We have studied the global cloud distribution on Mars using red and blue global map swaths taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC).
\r\n\r\nIn Chapters 1 and 4, we summarize the results for the first and second MGS mapping years, respectively. In Chapter 2, we investigate the mechanism for a new type of \"flushing\" dust storm first observed by MGS. These dust storms moved from the northern high latitudes southward across the equator, and led to a planet-encircling dust storm in the first MGS mapping year (1999). In Chapter 3, we track cloud motion to measure winds using images separated by 2 hours.
\r\n\r\nThe systematic daily global coverage of MGS not only provides us with detailed and coherent pictures of Martian cloud evolution, but also increases the number of cloud-tracked wind vectors by three orders of magnitude. Except for the global dust storm in the second MGS mapping year (2001), Martian weather is highly repeatable. When the 2001 global dust storm initiated, Hellas storms increased in frequency, transporting dust out of the basin daily. When the 1999 planet-encircling dust storm initiated, \"flushing\" storms also increased in frequency, transporting dust to the southern subtropics daily. These observations suggest that timely dust supply by local or regional storms could have a global impact.
", "doi": "10.7907/CYNM-8830", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:934", "collection": "thesis", "collection_id": "934", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03122003-112232", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 1586608, "license": "other", "mime_type": "application/pdf", "url": "/934/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High-Precision Infra-Red Stellar Interferometry", "author": [ { "family_name": "Lane", "given_name": "Benjamin Frederick", "orcid": "0000-0002-8006-0243", "clpid": "Lane-Benjamin-Frederick" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Colavita", "given_name": "M. Mark", "clpid": "Colavita-M-M" }, { "family_name": "Brown", "given_name": "Michael E.", "clpid": "Brown-M-E" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "clpid": "Kulkarni-S-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This dissertation describes work performed at the Palomar Testbed Interferometer (PTI) during 1998-2002. Using PTI, we developed a method to measure stellar angular diameters in the 1-3 milli-arcsecond range with a precision of better than 5%. Such diameter measurements were used to measure the mass-radius relations of several lower main sequence stars and hence verify model predictions for these stars. In addition, by measuring the changes in Cepheid angular diameters during the pulsational cycle and applying a Baade-Wesselink analysis we are able to derive the distances to two galactic Cepheids (eta Aql and zeta Gem) with a precision of order 10%; such distance determinations provide an independent calibration of the Cepheid period-luminosity relations that underpin current estimates of cosmic distance scales.
\r\n\r\nSecond, we used PTI and the adaptive optics facility at the Keck Telescope on Mauna Kea to resolve the low mass binary systems BY Dra and GJ 569B, resulting in dynamical mass determinations for these systems. GJ 569B most likely contains at least one substellar component, and as such represents the first dynamical mass determination of a brown dwarf.
\r\n\r\nFinally, a new observing technique - dual-star phase referencing - was developed and demonstrated at PTI. Phase referencing allows interferometric observations of stars previously too faint to observe, and is a prerequisite for large-scale interferometric astrometry programs such as the one planned for the Keck Interferometer; interferometric astrometry is a promising technique for the study of extra-solar planetary systems, particularly ones with long-period planets.
", "doi": "10.7907/618C-6550", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2232", "collection": "thesis", "collection_id": "2232", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292003-140024", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 7693697, "license": "other", "mime_type": "application/pdf", "url": "/2232/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "History and Current Processes of the Martian Polar Layered Deposits", "author": [ { "family_name": "Byrne", "given_name": "Shane", "orcid": "0000-0002-6735-4685", "clpid": "Byrne-Shane" } ], "thesis_advisor": [ { "family_name": "Gurnis", "given_name": "Michael C.", "clpid": "Gurnis-M-C" } ], "thesis_committee": [ { "family_name": "Brown", "given_name": "Michael E.", "clpid": "Brown-M-E" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Richardson", "given_name": "Mark I.", "clpid": "Richardson-M-I" }, { "family_name": "Gurnis", "given_name": "Michael C.", "clpid": "Gurnis-M-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Martian polar layered deposits constitute a detailed record of geologically recent environmental conditions. In this thesis I examine processes that have affected this history over timescales ranging from \u224810\u00b2 to \u224810\u2077 Martian years. To complete the work in this thesis I developed a geographic database of the Martian polar regions to enable comparisons of different datasets spread over different missions.
\r\n\r\nI report on the discovery of a large sand rich unit underlying the northern polar layered deposits. The presence of this unit suggests there once existed a radically different polar environment where there was no polar cap. A major new question now arises of where that water went during this time period and how the old polar cap (if there was one) was removed.
\r\n\r\nI describe analysis and modeling of evolving landforms on the southern residual CO\u2082 cap. This modeling suggests that these landforms are underlain by a water ice layer. THEMIS observations were used to confirm this hypothesis. This limits the size of the residual CO\u2082 cap reservoir to no more than 5% of the current atmosphere, which puts an important constraint on models of atmospheric evolution. Analysis of the size distribution coupled with this modeling indicates a uniform age for a large group of these features, implying some environmental change on the order of Martian centuries ago.
\r\n\r\nI examined geomorphologic evidence for flow processes at the margin of the south polar layered deposits. Indications of multiple episodes of previous flow are seen. However much evidence of brittle processes such as faulting, slumping and landsliding is also present. This leads to the conclusion that, during some periods, flow of the layered deposits is incapable of relieving the gravitationally generated stresses within the ice sheet. The evidence suggests that periods where flow was possible occurred intermittently and were separated by periods in which sublimation-based retreat of the ice dominated.
", "doi": "10.7907/XRZN-4T75", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:877", "collection": "thesis", "collection_id": "877", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03052003-124751", "primary_object_url": { "basename": "fenton_phd_doubleside.pdf", "content": "final", "filesize": 8755188, "license": "other", "mime_type": "application/pdf", "url": "/877/11/fenton_phd_doubleside.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Aeolian Processes on Mars: Atmospheric Modeling and GIS Analysis", "author": [ { "family_name": "Fenton", "given_name": "Lori Kay", "orcid": "0000-0001-8116-4901", "clpid": "Fenton-Lori-Kay" } ], "thesis_advisor": [ { "family_name": "Brown", "given_name": "Michael E.", "clpid": "Brown-M-E" } ], "thesis_committee": [ { "family_name": "Brown", "given_name": "Michael E.", "clpid": "Brown-M-E" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Sieh", "given_name": "Kerry E.", "clpid": "Sieh-K-E" }, { "family_name": "Richardson", "given_name": "Mark I.", "clpid": "Richardson-M-I" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Wind is currently the dominant geological agent acting on the surface of Mars. A study of Martian aeolian activity leads to an understanding of the forces that have sculpted the planet's face over the past billion years or more and to the potential discovery of climate shifts recorded in surface wind features that reflect ancient wind patterns. This work takes advantage of newly available tools and data to reconstruct the sedimentary history reflected in aeolian features on Mars. The thesis is divided into two main projects. In the first section, a widely accepted hypothesis, that oscillations in Martian orbital parameters influence atmospheric circulation patterns, is challenged. A Mars global circulation model is run at different obliquity, eccentricity, and perihelion states and the predicted surface wind orientations are correlated with observed aeolian features on the Martian surface. The model indicates that orbital parameters have little effect on wind patterns, suggesting that aeolian features not aligned with the current wind regime must have formed under atmospheric conditions unrelated to orbital parameters. In the second project, new spacecraft data and a mesoscale model are used to determine the sedimentary history of Proctor Crater, a 150 km diameter crater in the southern highlands of Mars. Using high-resolution imagery, topography, composition, and thermal information, a GIS was constructed to study the aeolian history of the crater, which was found to have a complex interaction of deposition and erosion. Surficial features include 450 m of sediments filling the crater basin, small bright bedforms, dust devil tracks, and a dark dunefield consisting of coarse, basaltic sand and containing slipfaces indicative of a multidirectional, convergent wind regime. All wind features, both ancient and contemporary, are coaligned, indicating that formative wind directions have changed little since the first aeolian features formed in this area. Mesoscale model runs over Proctor Crater indicate that two dune slipfaces are created by winter afternoon geostrophic westerlies and summer evening katabatic easterlies, and that dust devil tracks are created by summer noontime rotational westerlies. Using all available tools, this thesis begins the work of understanding how aeolian processes have influenced the Martian surface.\r\n", "doi": "10.7907/C9V4-8050", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:4431", "collection": "thesis", "collection_id": "4431", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11072001-160517", "primary_object_url": { "basename": "01title_page.pdf", "content": "final", "filesize": 35117, "license": "other", "mime_type": "application/pdf", "url": "/4431/1/01title_page.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Low Order Model of Martian Circulation and Interannual Variability of Global Dust Storms", "author": [ { "family_name": "Pankine", "given_name": "Alexey Anatolyevich", "clpid": "Pankine-Alexey-Anatolyevich" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "The main theme of this work is the development of a simplified model of the martian circulation suitable for conducting computationally fast long term simulations of the martian climate system. In particular, we are looking for causes of the irregular occurrence of the martian global dust storms (GDSs). The low-order model (LOM) is constructed by Galerkin projection of a 2D (zonally averaged) general circulation model (GCM) onto a truncated set of basis functions. The resulting low-order model consists of twelve coupled nonlinear ordinary differential equations (ODEs). The forcing of the model is described by simplified physics based on Newtonian cooling and Rayleigh friction. The atmosphere and surface are coupled: atmospheric heating depends on the dustiness of the atmosphere, and the surface dust source depends on the strength of the atmospheric winds. Parameters of the model are tuned to fit output of the NASA Ames GCM.
\r\n\r\nThe model performance is examined for different seasons and dust opacities and it is found that the simulated mean meridional circulation and temperature fields compare well with the more sophisticated GCM. The time of occurence and duration of the global dust storms produced by the model compare well with observations by Viking Landers (VLs). The intensity of the meridional circulation as simulated by the LOM during northern summer is stronger than that predicted by the GCM. The situation can be improved if the Rayleigh friction varies seasonally. The LOM uncoupled from the dust source can be further simplified to form the Lorenz system with forcing.
\r\n\r\nThe model is applied to the problem of interannual variability of martian global dust storms. Basic hypotheses of the intrinsic and of the extrinsic irregularity of the martian climate system are tested. The intrinsic irregularity hypothesis implies that the system under consideration is chaotic, so that small variations in initial conditions make the behavior of the system essentially unpredictable. Different paths taken by the system in state space would correspond to years with and without a GDS. The extrinsic irregularity hypothesis, on the other hand, implies that without noise the system behaves periodically, but stochastic forcing of the system causes it to behave irregularly. It is concluded that the observed variability of GDSs is more easily explained by extrinsic irregularity. The stochastic forcing (``noise') could be provided by transient weather systems or some surface process, like size sorting or redistribution of the sand particles in the ``active' (i.e., storm generating) zones on the surface. The results are very sensitive to the value of the saltation threshold, which hints at the possible feedback between saltation threshold and dust storm activity. According to this hypothesis, the saltation threshold has adjusted its value so that dust storms are barely able to occur.
", "doi": "10.7907/MGSA-ZT98", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:7438", "collection": "thesis", "collection_id": "7438", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01252013-101859233", "primary_object_url": { "basename": "Lee-yt-2001.pdf", "content": "final", "filesize": 27988916, "license": "other", "mime_type": "application/pdf", "url": "/7438/1/Lee-yt-2001.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Atmospheric Chemistry and Transport Modeling in the Outer Solar System", "author": [ { "family_name": "Lee", "given_name": "Yuan-Tai", "clpid": "Lee-Yuan-Tai" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "This thesis consists of 1-D and 2-D photochemical dynamical modeling in the upper atmospheres of outer planets. For 1-D modeling, a unified hydrocarbon photochemical model has been studied in Jupiter, Saturn, Uranus, Neptune, and Titan, by comparing with the Voyager observations, and the recent measurements of methyl radicals by ISO in Saturn and Neptune. The CH_3 observation implies a kinetically sensitive test to the measured and estimated hydrocarbon rate constants at low temperatures. We identify the key reactions that control the concentrations of CH_3 in the model, such as the three-body recombination reaction, CH_3 + CH_3 + M \u2192 C_(2)H_6 + M, and the recycling reaction H + CH_3 + M \u2192CH_4 + M. The results show reasonable agreement with ISO values. In Chapter 4, the detection of PH_3 in the lower stratosphere and upper troposphere of Jupiter has provided a photochemical-dynamical coupling model to derive the eddy diffusion coefficient in the upper troposphere of Jupiter. Using a two-layers photochemical model with updated photodissociation cross-sections and chemical rate constants for NH_3 and PH_3, we find that the upper tropospheric eddy diffusion coefficient <10^5 cm^2 sec^(-1) and the deeper tropospheric value >10^6 cm^2 sec^(-1) are required to match the derived PH_3 vertical profile by the observation. The best-fit functional form derivation of eddy diffusion coefficient in the upper troposphere of Jupiter above 400 mbar is K = 2.0 x 10^4 (n/2.2 x 10^19)^(-0.5)cm^2 sec^(-1). On the other hand, Chapter 5 demonstrates a dynamical-only 2-D model of C_(2)H_6 providing a complete test for the current 2-D transport models in Jovian lower stratosphere and upper troposphere (270 to 0.1 mbar pressure levels). Different combinations of residual advection, horizontal eddy dispersion, and vertical eddy mixing are examined at different latitudes.
\r\n", "doi": "10.7907/y7ep-g464", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:7433", "collection": "thesis", "collection_id": "7433", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01242013-112821494", "primary_object_url": { "basename": "Toigo 2001.pdf", "content": "final", "filesize": 34046802, "license": "other", "mime_type": "application/pdf", "url": "/7433/1/Toigo 2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Behavior of Dust in the Martian Atmosphere", "author": [ { "family_name": "Toigo", "given_name": "Anthony Domenick", "clpid": "Toigo-Anthony-Domenick" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" }, { "family_name": "Richardson", "given_name": "Mark I.", "clpid": "Richardson-M-I" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Two aspects of the dust cycle on Mars are examined: the seasonal variation of dust aerosols\r\nin the atmosphere as observed by spacecraft and dust lifting by high wind stress at the south\r\npole during late spring employing a specially developed mesoscale atmospheric model. Reanalysis\r\nof Viking mission optical depth measurements shows that the visible to infrared\r\nratio of total extinction opacity varies with season, and is due to seasonally varying water\r\nice haze. The Martian atmosphere is clearer of dust, especially during northern spring and\r\nsummer, than previously thought. Water ice hazes can provide roughly 50% of the total\r\nvisible opacity in these seasons, and that they represent only 1-5% of the total water column.\r\nNext, the conversion for use on Mars of a terrestrial mesoscale atmospheric model\r\n(the Mars MM5) is presented and described. Validation of the Mars MM5 is conducted\r\nby comparison with a general circulation model on scales of a few hundred kilometers and\r\nwith Martian surface landers (Viking Lander 1, Viking Lander 2, and Mars Pathfinder)\r\non scales of a few kilometers, and in both cases there is good agreement in the meteorological\r\nvariables of temperature, pressure, and wind. Tides are found to be at least as\r\nimportant as slopes in generating the diurnal cycle of winds at the lander sites, in contrast\r\nto previous one-dimensional studies. Finally, assuming that dust injection is related to the\r\nmovement of sand-sized grains or aggregates, the Mars MM5 predicts wind stresses of sufficient\r\nstrength to initiate movement of sand-sized particles, and hence dust lifting, during\r\nlate southern spring in the south polar region. It is found that the direct cap edge thermal\r\ncontrast provides the primary drive for high surface wind stresses at the cap edge at this season\r\nwhile sublimation flow is not found to be particularly important. Comparison between\r\nsimulations, in which dust is injected when wind stresses are high and those with inactive\r\ndust injection, show no signs of consistent feedback due to dust clouds on the surface wind stress fields during the late spring season examined here.\r\n", "doi": "10.7907/7v06-j640", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:8210", "collection": "thesis", "collection_id": "8210", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022014-104651690", "primary_object_url": { "basename": "Okin_gs_2001.pdf", "content": "final", "filesize": 60114054, "license": "other", "mime_type": "application/pdf", "url": "/8210/1/Okin_gs_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Wind, Driven Desertification: Process Modeling, Remote Monitoring, and Forecasting", "author": [ { "family_name": "Okin", "given_name": "Gregory Stewart", "orcid": "0000-0002-0484-3537", "clpid": "Okin-Gregory-Stewart" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" } ], "thesis_committee": [ { "family_name": "Randerson", "given_name": "James T.", "orcid": "0000-0001-6559-7387", "clpid": "Randerson-J-T" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Schlesinger", "given_name": "William H.", "clpid": "Schlesinger-W-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Arid and semiarid landscapes comprise nearly a third of the Earth's total land surface. These areas are coming under increasing land use pressures. Despite their low productivity these lands are not barren. Rather, they consist of fragile ecosystems vulnerable to anthropogenic disturbance.
\r\n\r\nThe purpose of this thesis is threefold: (I) to develop and test a process model of wind-driven desertification, (II) to evaluate next-generation process-relevant remote monitoring strategies for use in arid and semiarid regions, and (III) to identify elements for effective management of the world's drylands.
\r\n\r\nIn developing the process model of wind-driven desertification in arid and semiarid lands, field, remote sensing, and modeling observations from a degraded Mojave Desert shrubland are used. This model focuses on aeolian removal and transport of dust, sand, and litter as the primary mechanisms of degradation: killing plants by burial and abrasion, interrupting natural processes of nutrient accumulation, and allowing the loss of soil resources by abiotic transport. This model is tested in field sampling experiments at two sites and is extended by Fourier Transform and geostatistical analysis of high-resolution imagery from one site.
\r\n\r\nNext, the use of hyperspectral remote sensing data is evaluated as a substantive input to dryland remote monitoring strategies. In particular, the efficacy of spectral mixture analysis (SMA) in discriminating vegetation and soil types and detennining vegetation cover is investigated. The results indicate that hyperspectral data may be less useful than often thought in determining vegetation parameters. Its usefulness in determining soil parameters, however, may be leveraged by developing simple multispectral classification tools that can be used to monitor desertification.
\r\n\r\nFinally, the elements required for effective monitoring and management of arid and semiarid lands are discussed. Several large-scale multi-site field experiments are proposed to clarify the role of wind as a landscape and degradation process in dry lands. The role of remote sensing in monitoring the world's drylands is discussed in terms of optimal remote sensing platform characteristics and surface phenomena which may be monitored in order to identify areas at risk of desertification. A desertification indicator is proposed that unifies consideration of environmental and human variables.
", "doi": "10.7907/7ND2-DH05", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:903", "collection": "thesis", "collection_id": "903", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03092004-155058", "primary_object_url": { "basename": "Tulaczyk_s_1999.pdf", "content": "final", "filesize": 17782172, "license": "other", "mime_type": "application/pdf", "url": "/903/1/Tulaczyk_s_1999.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Basal mechanics and geologic record of ice streaming, West Antarctica", "author": [ { "family_name": "Tulaczyk", "given_name": "Slawek M.", "clpid": "Tulaczyk-Slawek-M" } ], "thesis_advisor": [ { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" } ], "thesis_committee": [ { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Engelhardt", "given_name": "Hermann", "clpid": "Engelhardt-H" }, { "family_name": "Scott", "given_name": "Ronald F.", "clpid": "Scott-R-F" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Piston coring in boreholes drilled at the UpB camp through Ice Stream B, West Antarctica, provided the first samples of sediments ever recovered from beneath an active ice stream. Sedimentological analyses indicate that the samples come from the layer of weak, subglacial till underlying this ice stream (the UpB till). Textural properties of the till and the Tertiary diatoms found in it suggest that the UpB till is recycled from the sediments of the inferred eastern subglacial extension of the Ross Sea sedimentary basin. Geotechnical tests show that the UpB till can be modeled as a compressible, Coulomb-plastic material whose strength is practically independent of deformation rate but is determined by effective stress which also determines the water content. Simulations of the subglacial behavior of such till have successfully reproduced fundamental features of the observed, subglacial till kinematics, e.g., viscous-like vertical distribution of strain and oscillations in tilt rates. The compressible-Coulomb-plastic till model offers a framework for understanding and modeling of ice stream motion and ice-till interactions. The high porosity of the UpB till ([approximately] 0.4) suggests that effective stress is consistently very low, ca. 0.1 to 30 kPa, in the subglacial zone of Ice Stream B. These conditions are explained by the 'undrained-bed' model of sub-ice-stream hydrology that includes only local exchange of water between the water stored in the till pore space and the water stored as basal ice. In this model, there is a negative feedback effect between the basal melting rate and till strength which forces a steady-state in which the basal melting rate is zero and the till is water-rich and weak. Coupling of the undrained-bed model with an equation for the velocity of ice stream sliding yields the undrained plastic-bed model of ice streaming (the UpB model). In accordance with the existing observations, the physics of the UpB model produces two stable modes: an active 'ice-stream' mode and an 'ice-sheet' mode. The model may experience thermally-triggered switches between the two modes and it can be used to test the hypothesis that the West Antarctic Ice Sheet will become unstable in the near-future.", "doi": "10.7907/N04E-S040", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:16178", "collection": "thesis", "collection_id": "16178", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09072023-170005385", "primary_object_url": { "basename": "Holt_JW_1997.pdf", "content": "final", "filesize": 65389008, "license": "other", "mime_type": "application/pdf", "url": "/16178/1/Holt_JW_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Detailed Records of Geomagnetic Field Behavior from Death Valley and Hawaii. II. An Age Constraint on Gulf of California Rifting from Santa Rosal\u00eda, Baja California", "author": [ { "family_name": "Holt", "given_name": "John William", "clpid": "Holt-John-William" } ], "thesis_advisor": [ { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "thesis_committee": [ { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Detailed records of geomagnetic field behavior were produced and analyzed from Plio/Pleistocene sedimentary rocks of Death Valley, California and from Pleistocene/Holocene volcanic rocks of Hawaii. These records provide new information about geomagnetic field polarity reversals, excursions, secular varia\u00adtion, and the paleomagnetic recording process in sediments. In addition, a magnetostratigraphic and geochronlogic study of Mio/Pliocene marine sedimen\u00adtary rocks in Baja California, Mexico was performed in order to provide a new age constraint on Gulf of California rifting.
\r\n\r\nThe paleomagnetic studies in Death Valley were undertaken on siltstones, sand\u00ad stones, and evaporites exposed along the southern Death Valley fault zone in the Confidence Hills. These rocks contain multiple records of the R\u00e9union and Olduvai normal-polarity subchrons (2.15 - 2.13 Ma and 1.95 - 1.79 Ma, respec\u00adtively) within rocks formed as a result of deposition in different subenvironments of a saline ephemeral lake, with an average deposition rate of ~ 30 cm/kyr. Variations in bedding attitudes between the exposed sections allow a fold test of paleomagnetic directions. Two records of the upper Olduvai polarity reversal were obtained which agree despite differences of lithology, depositional environ\u00adment, and structural tilting. These records indicate several phases of polarity shifts during the transition of the geomagnetic field from normal to reversed polarity. Transitional virtual geomagnetic poles (VGP's) lie in longitudinal bands ~ 90\u00b0 away from the sampling site longitude, vastly different from VGP's pro\u00adduced by studies in other locations around the world but consistent with site\u00ad dependent trends of VGP paths observed in global data compilations. Studies of the anisotropy of anhysteritic remanence conclude that inclination shallowing in sediments during periods of low ambient magnetic field intensity is a possible cause for this site dependence of VGP paths. However, some aspect of the transitional geomagnetic field is recorded by the sedimentary rocks of Death Valley whether or not inclination shallowing took place.
\r\n\r\nA detailed record of the R\u00e9union normal-polarity subchron was obtained from one of the sections in the Confidence Hills. This record shows that the R\u00e9union subchron was a single normal-polarity event of ~ 20 kyr duration, which is a significant finding due to the lack of previous data in this time interval. The pres\u00adence of a lithofacies which contains disruptive anhydrite crystals dispersed throughout the matrix creates two small gaps in the record just prior to the nor\u00admal-polarity R\u00e9union interval. Remagnetizations within this lithofacies facilitate the interpretation of the depositional environment responsible for growth of the disruptive evaporites.
\r\n\r\nSamples of the 1 km core produced by the Hawaii Scientific Drilling Project (HSDP) provided the basis for a study of geomagnetic field excursions and secular variation during the past 400 kyr at Hawaii. This core consists of over 200 lava flows erupted from Mauna Loa and Mauna Kea volcanoes. In contrast to previous hypotheses that the non-dipole field has been anomalously low in the central Pacific region for the past few hundred kyrs, the results of this study show that secular variation, and hence, the non-dipole field component, at Hawaii is consistent with secular variation elsewhere on the globe for the past 400 kyr. In addition, the data show evidence for a persistent axial quadrupole in the time\u00ad averaged field. This research also resulted in the first records of geomagnetic field excursions in the central Pacific which may be correlated with those found elsewhere on the globe, lending support to the hypothesis that these are global events rather than local perturbations of the geomagnetic field.
\r\n\r\nPaleomagnetic and geochronologic studies of marine sedimentary rocks in the Santa Rosal\u00eda basin, Baja California Sur, show that despite the presence of local copper ore deposition, primary magnetic remanence directions may be obtained from most of the marine sandstones overlying the basement in that area. Using preliminary magnetostratigraphy and an \u2074\u2070Ar/\u00b3\u2079Ar isotopic age of 6.76 \u00b1 0.45 Ma (1\u03c3) obtained for a volcanic unit interbedded with the sandstones, a correla\u00adtion with the geomagnetic polarity time scale was made possible, yielding an age of 7.1 \u00b1 0.05 Ma for the base of the marine section. This provides a new age constraint on Gulf of California rifting and may help to refine models of North America - Pacific plate boundary interactions during the period 12 - 3.5 Ma.
", "doi": "10.7907/y9sj-ca84", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:194", "collection": "thesis", "collection_id": "194", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01152008-142257", "primary_object_url": { "basename": "Packman_ai_1997.pdf", "content": "final", "filesize": 41426789, "license": "other", "mime_type": "application/pdf", "url": "/194/1/Packman_ai_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Exchange of colloidal kaolinite between stream and sand bed in a laboratory flume", "author": [ { "family_name": "Packman", "given_name": "Aaron Ian", "clpid": "Packman-A-I" } ], "thesis_advisor": [ { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "thesis_committee": [ { "family_name": "List", "given_name": "E. John", "clpid": "List-E-J" }, { "family_name": "Hering", "given_name": "Janet G.", "clpid": "Hering-J-G" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Experiments were conducted in a recirculating flume to study the exchange of colloids between a stream and sand bed. Observations of the net transport of kaolinite clay from the stream to the bed were used to validate models for colloid exchange which include the hydraulics of water exchange along with the particle-specific effects of filtration and settling.\r\n\r\nThe flume allowed extensive control of the stream conditions (slope, depth, velocity) and bed parameters (bed depth, bedform height, wavelength, and velocity). All experiments had steady, uniform stream flow and well-developed bedforms. To define the chemistry of the system, the composition of the flume water was controlled, the clay was reproducibly prepared, and the sand was cleaned prior to every experiment.\r\n\r\nExperiments involved observing the exchange of both a conservative lithium chloride tracer and the kaolinite tracer. Net exchange was determined by measuring the change of tracer concentration in the stream water. Vertical profiles of the tracer distribution in the bed were also measured.\r\n\r\nColumn experiments were performed to measure kaolinite filtration by the bed sediment. The pH and ionic strength of both the flume and column water were controlled to vary the extent of filtration.\r\n\r\nTwo mechanisms are responsible for exchange between the stream and stream bed--an advective pore-water flow driven by bedform-induced pressure variations at the surface of the bed (pumping), and the burial and release of water due to bedform motion (turnover). Pumping causes kaolinite to be carried deep in the bed where it is trapped due to filtration and settling. Turnover causes continuous mixing of the uppermost portion of the bed which hinders penetration of clay to the deeper bed.\r\n\r\nModels incorporating the relevant physical and chemical processes controlling colloid transport were developed to predict the net exchange of kaolinite between the stream and sand bed. Model parameters were nondimensionalized so the models can be applied to problems of any scale. Models for conservative solutes were developed to predict the exchange with a finite bed and exchange due to fast-moving bedforms. Models for colloid transport were developed which are based on the solute transport models, but include the impact of settling on particle flow paths and filtration along path lines. When input data were taken from laboratory experiments, the models generally predicted the flume results well with no calibration. In all flume experiments, filtration and settling of colloids in the bed were sufficiently high so that it could be assumed that all colloid which entered the bed was irreversibly trapped.\r\n\r\nAdditional model simulations were performed to demonstrate the effect of major input variables on exchange. These simulations cover cases not examined in experiments and provide a sensitivity analysis for the model inputs.\r\n", "doi": "10.7907/FYMP-BR13", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5516", "collection": "thesis", "collection_id": "5516", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01132010-093747416", "primary_object_url": { "basename": "Nagy_ea_1997.pdf", "content": "final", "filesize": 17758433, "license": "other", "mime_type": "application/pdf", "url": "/5516/1/Nagy_ea_1997.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Extensional Deformation and Volcanism Within the Northern Puertecitos Volcanic Province, Sierra Santa Isabel, Baja California, Mexico", "author": [ { "family_name": "Nagy", "given_name": "Elizabeth Ann", "clpid": "Nagy-Elizabeth-Ann" } ], "thesis_advisor": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Farley", "given_name": "Kenneth A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Geologic features at the western edge of the Gulf Extensional Province (GEP) in northeastern Baja California, Mexico, record details of Pacific-North American (PAC-NAM) plate boundary history prior to and during its establishment within the Gulf of California. Methods of study in Santa Isabel Wash (SIW) (informally named) in the northern Sierra Santa Isabel include geologic mapping of ~140 km^2 (1:20000 scale) along the northern margin of the Miocene-Pliocene Puertecitos Volcanic Province (PVP), ^(40)Ar/^(39)Ar geochronology, electron microprobe analysis, paleomagnetic study, and petrography. Local Neogene stratigraphy (spanning ~17-6 Ma) includes volcaniclastic breccias, basaltic to dacitic lava flows, and rhyolitic pyroclastic flow deposits. The completeness of the lithologic package improves stratigraphic correlations between the PVP and nearby regions.
\r\n\r\nHigh-angle extension-related faults cut all rocks in SIW. The southeastward projection of the pre-6 Ma Matorni accommodation zone, which separates a northern region of greater and more prolonged extension from a less extended southern zone, may pass on the north side of SIW. Paleomagnetic analysis indicates no vertical axis rotations in SIW since 6 Ma. This contrasts with regions north of the Matomi accommodation zone where clockwise rotation has accompanied extensional deformation since 3-6 Ma. About 500 meters of post-6 Ma, E-side-down displacement occurs across two major, NNW-striking normal faults on the west side of SIW. These, and smaller synthetic and antithetic faults in the hanging walls, accommodate up to 4% E- to ENE-directed extension. Quaternary deformation is also documented.
\r\n\r\nA new model developed to explain ENE-directed extension in northeastern Baja California partitions present-day PAC-NAM plate motion between NNW-striking, sinistral dip-slip faults and N- to NNW-striking, dextral (oblique?) strike-slip fault(s) in the northernmost Gulf of California. The model offers explanations for the geometry of plate motion accommodation between the latitudes of the Agua Blanca fault and the PVP, bathymetric features near Wagner and Consag basins, the position and jumps of nearby spreading centers since 6 Ma, the greater width and bend in coastline of the northernmost Gulf of California, the incorporation of the PVP into the GEP 2-3 Ma, and suggests a transitional tectonic scenario between oceanic spreading centers and continental transforms (\"Wagner Transition Zone\").
", "doi": "10.7907/znpy-3311", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5736", "collection": "thesis", "collection_id": "5736", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04222010-100328955", "primary_object_url": { "basename": "Haldemenn_afc_1997.pdf", "content": "final", "filesize": 37232907, "license": "other", "mime_type": "application/pdf", "url": "/5736/1/Haldemenn_afc_1997.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Interpreting Radar Scattering: Circular-Polarization Perspectives from Three Terrestrial Planets", "author": [ { "family_name": "Haldemann", "given_name": "Albert Frank Christian", "clpid": "Haldemann-Albert-Frank-Christian" } ], "thesis_advisor": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Planetary radar astronomy has used circular polarization radar signals to probe the surfaces of many solar system targets. However the trend for terrestrial observations has been toward greater use of linearly polarized imaging radars. Fortunately the latest generation of imaging radars has been developed with a multi-polarization capability. This should allow a synergy of the two research communities to occur.
\r\n\r\nOne of the unresolved debates on planetary radar astronomy is the nature of the scattering processes from cold planetary ices. This question recently received input from a terrestrial source: Greenland (Rignot et al. 1993). In this thesis a survey is made of high altitude sites to discover if the Greenland percolation zone scattering behavior is wide-spread on the Earth. The survey was carried out with the enormous, publicly available dataset from the 1994 missions of Shuttle Imaging Radar payload. This instrument (SIR-C) obtained full-polarization information with its linear-polarization system. These data allow reconstruction of circular polarizations for comparison to planetary results. The search proved fruitful. Hundreds of square kilometers in western Tibet's Kunlun Shan, and in the Central Andes at the latitude of Santiago display radar scattering behavior quite similar to that in Greenland where internal reflections of the radar waves within icy inclusions in the firn enhance scattering in the same sense of circular polarization.
\r\n\r\nA separate unresolved issue in the planetary radar astronomy is the question of the nature of the highlands of Venus that exhibit high radar reflectivity and low emissivity. These so-called anomalous radar behavior in these regions have alternately been ascribed to high-dielectric doping or low dielectric volume scatterinig. We present new dual circular-polarization radar maps of the western hemisphere of Venus. The results are from a 1993 experiment to image Venus with 3.5 cm radar. Maps of Venusian radar albedo were made for each of two days of observation in both OS (echo principally due to specular reflection) and SS (diffuse echo) channels. On both days, the sub-earth longitude was near 300E. The SS maps are dominated by a significant component of diffuse backscatter from the 285E longitude highlands: Beta, Phoebe, and Themis Regiones. Beta Regio includes previously observed radar-anomalous regions. The nature of these altitude-related electrical properties on Venus is one of the outstanding surface process questions that remain after the Magellan mission. Our experiment provides the first full-disk polarization ratio (\u00b5_c) maps. The data show that different geology determines different radar scattering properties within Beta. Diffuse scattering is very important in Beta, and may be due to either surface or volume scattering. We find a strong correlation of the SS albedo \u03c3_(SS) with altitude R_p (km) in Beta, \u03c3_(SS) \u221d0.3R_p. Also, \u03c3_(OS) \u221d0.7 R_p. The onset of this relationship is at the R_p~6054 km planetary radius contour. The nature and morphology of the highland radar anomalies in Beta is consistent with a diffuse scattering mechanism. In Beta Regio we find \u00b5_c > 0.5 in general, with \u00b5_c as high as 0.8 between Rhea and Theia Montes, to the west of Devana Chasma. These values are compatible with measurements of blocky terrestrial lava flows if surface scattering dominates. If volume scattering is important, the high RCP cross-sections may indicate an important decrease in embedded scatterer size with altitude, which could be related to enhanced weathering.
\r\n\r\nFinally, the techniques of planetary radar astronomy were used in an applied sense. Results are presented of 3.5-cm delay-Doppler and Doppler-only (continuous wave or CW) radar experiments to assess three potential Mars Pathfinder landing sites: Ares Vallis, Tritonis Lacus, and northwest (NW) Isidis. The regional relief at all of the landing sites is appropriate for a Pathfinder landing sequence: east-west slopes do not exceed 3\u00b0 at any of the sites. We find that Ares Vallis has a Hagfors rms slope of \u03b8_(rms)=4.8\u00b0\u00b11.1\u00b0 as measured by delay-Doppler radar, and \u03b8_(rms)=6.4\u00b0\u00b10.6\u00b0 measured by CW radar. These values are similar to, or less than the previous measurements of the Viking Lander 1 region (\u03b8_(rms)=6\u00b0, Tyler et al. 1976, Harmon 1997). The Tritonis Lacus landing site is rougher with delay- Doppler, \u03b8_(rms)=5.6\u00b0\u00b10.6\u00b0, while the NW Isidis landing site is very smooth, both in a regional sense (slopes < 0.7\u00b0) and in a Hagfors rms slope sense: \u03b8_(rms)=1.8\u00b0\u00b10.2\u00b0. Reflectivities at all of the sites should be sufficient to allow the radar altimeter on Pathfinder to function properly.
\r\n", "doi": "10.7907/YQ6F-ZS42", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:4423", "collection": "thesis", "collection_id": "4423", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-083125", "primary_object_url": { "basename": "Ray_tw_1995.pdf", "content": "final", "filesize": 60568633, "license": "other", "mime_type": "application/pdf", "url": "/4423/1/Ray_tw_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Remote monitoring of land degradation in arid/semiarid regions", "author": [ { "family_name": "Ray", "given_name": "Terrill Wylie", "clpid": "Ray-T-W" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Anderson", "given_name": "Donald L.", "clpid": "Anderson-D-L" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Blom", "given_name": "Ron", "clpid": "Blom-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nLand degradation is a serious and growing problem on a world-wide scale -- 11% of the Earth's vegetated surface having suffered serious damage in the last 45 years. Human activity, especially sprinkler irrigation agriculture, can cause dramatic changes in arid regions as the fragile natural plant cover is stripped off and its root system destroyed in the process of cultivation. Satellite and airborne remote sensing data covering the Manix Basin of Eastern California over the last two decades shows that abandoned fields there suffered progressive degradation, as the topsoil eroded due to the lack of protective plant cover. Blowing sand buried and disrupted the downwind plant cover, which caused the downwind area to lose its protection against wind erosion and expanded the region of damage.\r\n\r\nBecause the amount and kind of plant cover is an important marker both of where wind erosion has occurred and where it is likely to occur in the future, especially designed satellite monitoring systems should be able to sense to signatures of undisturbed and disturbed vegetation cover in arid regions. However, this problem cannot be addressed by standard vegetation indices, because of the adaptation of arid region plants to the scarcity of water. Furthermore, weekly to monthly sampling will be necessary because blowing sand visible to satellite remote sensing is highly dependent on the local weather, and this can change within a few months. A new vegetative index suitable for arid regions is proposed for the wavelength region from 0.4-1.0 [...].\r\n\r\nThe detection and identification of arid region plant communities requires a highly calibrated remote sensing system with higher spectral resolution than that currently offered by Landsat Thematic Mapper. The way in which regions of blowing sand can appear and disappear with rapidity demonstrates the need for a remote monitoring system that can survey large areas on a regular basis. Such a system must be supported by focused ground observations and a continuing analysis of the satellite data.\r\n", "doi": "10.7907/65EA-Y568", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4414", "collection": "thesis", "collection_id": "4414", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11052007-080036", "primary_object_url": { "basename": "Stephens_sk_1995.pdf", "content": "final", "filesize": 8685339, "license": "other", "mime_type": "application/pdf", "url": "/4414/1/Stephens_sk_1995.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Carbonate formation on Mars : experiments and models", "author": [ { "family_name": "Stephens", "given_name": "Stuart Keller", "clpid": "Stephens-S-K" } ], "thesis_advisor": [ { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe experiments reported in this thesis were motivated by a desire to explain the small present [...] pressure in the Martian atmosphere, given the hypothesis that Mars once possessed a much denser [...] atmosphere. We adopted the premise that carbonate production on the surfaces of regolith particles, mediated by small amounts of [...], might explain the decline in the surface pressure over geologic timescales.\r\n\r\n\tWe exposed powders [...] of basalt glass, and of monominerallic diopside, olivine, plagioclase, and quartz, to conditions simulating the past and present surface of Mars ([...], and [...] contents equivalent to <1 to >5000 monolayers on particle surfaces). A sensitive manometer was used to acquire precise measurements of pressure over periods of [...] days. Initial pressure drops were attributed to adsorption of [...] on particle surfaces and dissolution of [...]. Continuing uptake of gas in most experiments suggested that [...] reacted with powders to form carbonate. Fits to [...] after [...] day gave [...], implying logarithmic reaction kinetics (i.e., reaction rate, [...]. Subsequent fits to [...], incorporating adsorption and dissolution, gave rates of D = 0.01-2 monolayers [...] per [...], with [...] day. Reaction amounts totaled [...] monolayers. Parabolic kinetics, arising from diffusion through a product layer, probably did not exceed P(t) [...]\r\n\r\nRates varied with sample composition (basalt and diopside > olivine > plagioclase and quartz). Basalt glass was not more reactive than diopside. Basalt powder pretreated with weak acid displayed rates reduced by over an order of magnitude (although diopside did not), suggesting something removed by acid contributes to [...] uptake. Rates increased with [...] content, temperature, and CO2 pressure, vA fit to data for basalt at 295 K gave [...], where H is [...] content in monolayers and D is in monolayers [...] per log [...]t; at 248-263 K, the-effect of [...] is stronger: [...]. [...] for \"dry\" experiments; no lower limit was put on [...] required for reaction.\r\n\r\nReflectance spectra at mid-infrared wavelengths [...] were obtained for all \"dry\" and \"vapor\" experimental powders, and ratioed to starting spectra for maximum sensitivity to added phases. Prominent spectral features near [...] in basalt and diopside coincided with [...] absorptions at 6.9 [...] for calcite. Additional absorptions near 6.1 [...] in basalt and 4.0 [...] in diopside were also consistent with the presence of calcite. Absorption ratios near 7 [...] ranged from [...] (corresponding to perhaps 3 wt% added calcite) to as little as [...], below which we were unable to identify added phases. There was a clear positive correlation between absorption ratios and experimental [...] uptakes (and hence [...] content), strengthening the conclusion that carbonate--probably calcite but perhaps magnesite or dolomite--formed in pressure-drop experiments.\r\n\r\nOur experiments suggested that this process does occur, but modeling and application to Mars indicated that it may be insufficient to explain the carbonate production required to reduce atmospheric pressure by [...] bar over geologic time. The principal difficulty lies in the lack of evidence for the reaction proceeding easily beyond one monolayer of product. Although some experiments displayed evidence for the growth of more than a monolayer, they also showed that this arises in a regime of logarithmic reaction kinetics, where [...] uptake is limited by declining surface area available for reaction. For a global layer of basalt powder, only high specific surface area [...], a deep regolith (>100 m), or plentiful [...] (equivalent to films >5 monolayers thick) allow total [...] stored as carbonate to exceed [...] mb. Diffusion-limited kinetics were not ruled out for timescales much longer than experimental durations, and models with thicker carbonate growths show that this could account for storage of an early Martian atmosphere.\r\n\r\nOther mechanisms for the loss of [...] may also contribute in the transition to the present surface pressure. Or, Mars may simply never have had a dense, [...] atmosphere, although this requires explanations other than a [...] greenhouse for the morphological features used to support the hypothesis of a warm, wet early Mars. If large amounts of carbonate minerals do represent a sink for atmospheric [...], the question of their location on the surface still remains since they have not been confirmed spectroscopically.\r\n", "doi": "10.7907/PSFY-MZ22", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4424", "collection": "thesis", "collection_id": "4424", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-091745", "primary_object_url": { "basename": "Leshin_la_1995.pdf", "content": "final", "filesize": 11818246, "license": "other", "mime_type": "application/pdf", "url": "/4424/1/Leshin_la_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Abundance and Hydrogen Isotopic Composition of Water in SNC Meteorites: Implications for Water on Mars", "author": [ { "family_name": "Leshin", "given_name": "Laurie Ann", "clpid": "Leshin-Laurie-Ann" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Burnett", "given_name": "Donald S.", "clpid": "Burnett-D-S" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Wyllie", "given_name": "Peter J.", "clpid": "Wyllie-P-J" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "Caltech Distinguished Alumni Award" }, { "literal": "div_gps" } ], "abstract": "The water in the current martian atmosphere contains ~5 times more deuterium (D) than water on Earth (corresponding to a \u03b4D value of ~+4000) resulting from preferential loss of hydrogen relative to deuterium from the martian atmosphere. This thesis places constraints on the D/H of other martian water reservoirs by measuring the D/H of water in hydrous phases within the SNC meteorites, thought to be samples of martian igneous rocks.
\r\n\r\nResults from vacuum extractions of volatiles from bulk SNC samples by stepwise heating show the water yields to decrease and \u03b4D values to increase to well above terrestrial values with increasing temperature, indicative of mixing between terrestrial ~+2000 for Shergotty, the most Denriched sample. However, even the highest \u03b4D values measured may represent lower limits on the true values due to partial exchange with lighter terrestrial water.
\r\n\r\nD/H and water contents of individual amphibole, biotite and apatite grains in several SNC meteorites were measured using an ion microprobe. The amphiboles contain an order of magnitude less water than previously assumed, suggesting that SNC parent magmas may have been less hydrous than previously proposed. The \u03b4D values of the phases range from ~+500 to +4300. The variability and D-enriched nature of these values imply that the primary igneous phases have not retained a martian magmatic water signature. Rather, the high and variable D/H of the water in these phases, like that released at high temperatures from bulk SNC samples, is concluded to result from the interaction of the samples with D-enriched martian crustal fluids after crystallization, probably in an environment similar to terrestrial magmatic hydrothermal systems.
\r\n\r\nThe data presented in this thesis represent the first direct evidence for ubiquitous crustal water-igneous rock interaction on another planet. Moreover, the results imply that a large amount of water must have been lost from the martian system since water in the martian crust, in addition to the atmosphere, appears to reflect D-enrichment processes.
", "doi": "10.7907/36AJ-NW91", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:7525", "collection": "thesis", "collection_id": "7525", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03182013-160237674", "primary_object_url": { "basename": "Keszthelyi_lp_1994.pdf", "content": "final", "filesize": 51471055, "license": "other", "mime_type": "application/pdf", "url": "/7525/1/Keszthelyi_lp_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "On the Thermal Budget of Pahoehoe Lava Flows", "author": [ { "family_name": "Keszthelyi", "given_name": "L\u00e1szl\u00f3 P.", "clpid": "Keszthelyi-L\u00e1szl\u00f3-P" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Taylor", "given_name": "Hugh P.", "clpid": "Taylor-H-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Denlinger", "given_name": "Roger", "clpid": "Denlinger-R" }, { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In this thesis I investigate some aspects of the thermal budget of pahoehoe lava\r\nflows. This is done with a combination of general field observations, quantitative\r\nmodeling, and specific field experiments. The results of this work apply to pahoehoe\r\nflows in general, even though the vast bulk of the work has been conducted on the lavas\r\nformed by the Pu'u 'O'o - Kupaianaha eruption of Kilauea Volcano on Hawai'i. The field\r\nobservations rely heavily on discussions with the staff of the United States Geological\r\nSurvey's Hawaiian Volcano Observatory (HVO), under whom I labored repeatedly in\r\n1991-1993 for a period totaling about 10 months.
\r\n\r\nThe quantitative models I have constructed are based on the physical processes\r\nobserved by others and myself to be active on pahoehoe lava flows. By building up these\r\nmodels from the basic physical principles involved, this work avoids many of the pitfalls of\r\nearlier attempts to fit field observations with \"intuitively appropriate\" mathematical\r\nexpressions. Unlike many earlier works, my model results can be analyzed in terms of the\r\ninteractions between the different physical processes. I constructed models to: (1) describe\r\nthe initial cooling of small pahoehoe flow lobes and (2) understand the thermal budget of\r\nlava tubes.
\r\n\r\nThe field experiments were designed either to validate model results or to constrain\r\nkey input parameters. In support of the cooling model for pahoehoe flow lobes, attempts\r\nwere made to measure: (1) the cooling within the flow lobes, (2) the amount of heat\r\ntransported away from the lava by wind, and (3) the growth of the crust on the lobes.\r\nField data collected by Jones [1992], Hon et al. [1994b], and Denlinger [Keszthelyi and\r\nDenlinger, in prep.] were also particularly useful in constraining my cooling model for\r\nflow lobes. Most of the field observations I have used to constrain the thermal budget of\r\nlava tubes were collected by HVO (geological and geophysical monitoring) and the Jet\r\nPropulsion Laboratory (airborne infrared imagery [Realmuto et al., 1992]). I was able to\r\nassist HVO for part of their lava tube monitoring program and also to collect helicopterborne\r\nand ground-based IR video in collaboration with JPL [Keszthelyi et al., 1993].
\r\n\r\nThe most significant results of this work are (1) the quantitative demonstration that\r\nthe emplacement of pahoehoe and 'a'a flows are the fundamentally different, (2)\r\nconfirmation that even the longest lava flows observed in our Solar System could have\r\nformed as low effusion rate, tube-fed pahoehoe flows, and (3) the recognition that the\r\natmosphere plays a very important role throughout the cooling of history of pahoehoe lava\r\nflows. In addition to answering specific questions about the thermal budget of tube-fed\r\npahoehoe lava flows, this thesis has led to some additional, more general, insights into the\r\nemplacement of these lava flows. This general understanding of the tube-fed pahoehoe\r\nlava flow as a system has suggested foci for future research in this part of physical\r\nvolcanology.
", "doi": "10.7907/G5V5-T293", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:7472", "collection": "thesis", "collection_id": "7472", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02112013-110255064", "primary_object_url": { "basename": "Betts 1994.pdf", "content": "final", "filesize": 50949690, "license": "other", "mime_type": "application/pdf", "url": "/7472/1/Betts 1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Thermal and visible studies of Mars using the Termoskan data set", "author": [ { "family_name": "Betts", "given_name": "Bruce Harold", "clpid": "Betts-B-H" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Paige", "given_name": "David", "clpid": "Paige-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "In February and March, 1989, the Termoskan instrument on board the Phobos '88\r\nspacecraft of the USSR acquired the highest spatial resolution thermal data ever obtained\r\nfor Mars, ranging in resolution from 300 m to 3 km per pixel. It simultaneously obtained\r\nbroad band visible channel data. The panoramas cover a large portion of the equatorial\r\nregion from 30\u00b0S to 6\u00b0N. New and unique analyses facilitated by Termoskan are\r\npresented here. In addition, this thesis describes the instrument, data, and validation.\r\nTermoskan thermal data shows good temperature agreement with Viking IRTM.\r\nHowever, conversion of Termoskan visible data to bolometric albedo is problematic.
\r\n\r\nUtilizing the Termoskan data, I recognized a new feature on Mars: ejecta blanket\r\ndistinct in the thermal infrared (EDITH). Virtually all of the more than 100 such features\r\ndiscovered in the Termoskan data are located on the plains near Valles Marineris. I\r\ncompiled a data base of 110 EDITH and non-EDITH craters ranging in diameter from 4.2\r\nkm to 90.6 km. EDITHs have a startlingly clear dependence upon terrains of Hesperian\r\nage, and show almost no other correlations within the data base. The Hesperian terrain\r\ndependence cannot be explained by either atmospheric or impactor variations. Wind\r\npatterns or locally available aeolian material cannot provide a single overall explanation for\r\nthe observed variations. I postulate that most of the observed EDITHs are due to\r\nexcavation of thermally distinctive Noachian age material from beneath a relatively thin\r\nlayer of younger, more consolidated Hesperian volcanic material. The plausibility of this\r\ntheory is supported by much geological evidence for relatively thin near-surface Hesperian\r\ndeposits overlying massive Noachian megabreccias on the EDITH-rich plains units. I\r\nsuggest that absence of thermally distinct ejecta blankets on Noachian and Amazonian\r\nterrains is due to absences of distinctive near-surface layering. Thermally distinct ejecta blankets are excellent locations for future landers and remote sensing because of relatively dust free surface exposures of material excavated from depth.
\r\n\r\nAlso included in the thermal images are observations of several major channel and\r\nvalley systems including significant portions of Shalbatana, Ravi, Al-Qahira, and Ma'adim\r\nValles, the channel south of Hydraotes Chaos, channel material in Eos Chasma, and small\r\nportions Simud, Tiu, and Ares Valles and channel material in Gangis Chasma.\r\nSimultaneous broad band visible data exists for all but Ma'adim Vallis. I find that most of\r\nthe channels and valleys have higher inertias than their surroundings, consistent with\r\nprevious thermal studies of martian channels. I show for the first time that thermal inertia\r\nboundaries closely match all flat channel floor boundaries. Using Viking albedos,\r\nTermoskan temperatures, and thermal modelling, I derive lower bounds on typical channel\r\nthermal inertias ranging from 8.4 to 12.5 (10^(-3) cal cm^(-2) s^(-1/2) K^(-1). Lower bounds on\r\ninertia differences with the surrounding heavily cratered plains range from 1.1 to 3.5.\r\nAtmospheric and geometric effects are not sufficient to cause the inertia enhancements. I\r\nagree with previous researchers that localized, dark, high inertia areas within channels are\r\nlikely aeolian in nature. However, thermal homogeneity and strong correlation of thermal\r\nboundaries with the channel floor boundaries lead me to favor non-aeolian overall\r\nexplanations. Small scale aeolian deposition or aeolian deflation may, however, play some\r\nrole in the inertia enhancement Channel floor inertia enhancements are strongly\r\nassociated with channels showing fretted morphologies such as wide, flat floors and steep\r\nscalloped walls. Therefore, I favor fretting processes over catastrophic flooding for\r\nexplaining the inertia enhancements. Fretting may have emplaced more blocks on channel\r\nfloors or caused increased bonding of fines due to increased availability of water.\r\nAlternatively, post-channel formation water that may have been preferentially present due\r\nto the low, flat fretted floors may have enhanced bonding of original fines or dust fallout\r\nThe coupling of both EDITHs and channel inertias to morphology is unlike most sharp\r\nMartian inertia variations which are decoupled from observed surface morphology.
\r\n\r\nTermoskan observed morning limb brightening in the thermal channel, but not in\r\nthe visible channel. The thermal morning limb brightening is likely due to a water ice or\r\ndust haze that is warmer than the surface at the time of the observations. A water ice haze\r\nwith a scale height of 5 km could match the observations. Visible scattering is observed to\r\nbe significant on morning and evening limbs out to 60 or 70 km. Localized high altitude\r\nstratospheric clouds are observed in the visible channel.
\r\n\r\nThe Termoskan data show that the highland-lowland boundary in the Aeolis\r\nQuadrangle appears strongly correlated with a high-low thermal inertia boundary. The\r\nsharpness of that boundary varies from less than 4 km to more than 50 km. In all cases,\r\ninertias continue to decrease gradually for many tens of km into the lowlands. Several\r\nother large scale thermal boundaries are also observed in the data.
\r\n\r\nTermoskan observed fine thermal structure on the flanks of Arsia Mons and\r\nelsewhere, which represent examples of interesting and significant thermal variations seen\r\nat the limit of Termoskan's spatial resolution. Sharp variations and boundaries imply there\r\ncannot be global scale dust blanketing deeper than about one centimeter, if that.
\r\n\r\nTermoskan obtained the first ever thermal images of Phobos' shadow on the\r\nsurface of Mars, along with simultaneous visible images. The best observed shadow\r\noccurrence was on the flanks of Arsia Mons. For this occurrence, I combined the\r\nobserved decrease in visible illumination of the surface with the observed decrease in\r\nbrightness temperature to calculate thermal inertias of the Martian surface. Most of the\r\nderived inertias fall within the range 0.9 to 1.4, corresponding to 5 to 10 micron dust\r\nparticles for a homogeneous surface. Dust at the surface is consistent with previous\r\ntheories of Tharsis as a current area of dust deposition. Shadow derived inertias are\r\nsensitive to mm depths, whereas diurnally derived inertias are sensitive to cm depths. The\r\nshadow derived inertias are very similar to Haberle and Jakosky [1991] atmospherically\r\ncorrected Palluconi and Kieffer [1981] Viking IRTM diurnally derived inertias. Thus, if\r\nnear surface layering exists at all in this region, it is not very significant.
\r\n\r\n\r\n", "doi": "10.7907/M9T5-G181", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:933", "collection": "thesis", "collection_id": "933", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03112009-141429", "primary_object_url": { "basename": "Svitek_t_1992.pdf", "content": "final", "filesize": 9657969, "license": "other", "mime_type": "application/pdf", "url": "/933/1/Svitek_t_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Martian water frost : control of global distribution by small-scale processes", "author": [ { "family_name": "Svitek", "given_name": "Tomas", "clpid": "Svitek-T" } ], "thesis_advisor": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis analyzes the small\u2014scale physical processes occurring in the Martian water polar frosts. The small\u2014scale processes are considered from the point of view of how they control the global distribution and behavior of water on Mars. The analysis of the small\u2014scale properties of the surface frost is essential in efforts to find solutions for some outstanding, contradictory observations, to interpret correctly remote sensing observations, to model the surface\u2014frost thermal balance, and to implement the boundary conditions and parameterizations used in the global models of the volatiles' behavior on Mars. Two different problems are investigated in this thesis:\r\n\r\nThe effect of surface roughness on frost temperature and morphology is studied in Chapter 2 and 3. The investigation of the temperature/roughness feedback leads to the following suggestion: There is a natural tendency of volatile surfaces to develop spontaneously small-scale roughness in a sublimation\u2014dominated environment. The evidence for this claim consists of the model of a rough\u2014surface thermal balance, and of the terrestrial analogs of differential sublimation structures. Such a phenomenon can be tested by the Mars Observer and has important implications for the behavior of water frost on Mars.\r\n\r\nViking Lander 2 winter\u2014frost observations are described in Chapter 4. This study suggests that winter water frost occurred there in two forms: a) thin, almost continuous, early frost, and b) much thicker, patchy, later frost with local cold\u2014trapping of water vapor playing the crucial role. This conclusion is based on the correlation of multiple data sets (from both Viking Orbiter and Lander) and on the combined models of the physical processes occurring on a small scale \u2014 below the resolution of remote sensing. The evidence consists of the frost\u2014surface coverage and color transitions, and of the calculation of the vertical and horizontal water\u2014vapor transport near the surface. Again, this phenomenon can be confirmed or rejected by a set of observations from the Mars Observer.\r\n\r\nThe inherent rough\u2014surface morphology and the frost cold\u2014trapping must be a general property of at least some forms of the seasonal and residual frosts. Both effects must be considered in order to understand the global observations of the Martian frost and the surface environment of Mars in general.\r\n", "doi": "10.7907/EDK8-3457", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:2512", "collection": "thesis", "collection_id": "2512", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06072007-141923", "type": "thesis", "title": "Quantitative Studies of the Martian South Polar Region Using Spacecraft Images", "author": [ { "family_name": "Herkenhoff", "given_name": "Kenneth Edward", "clpid": "Herkenhoff-Kenneth-Edward" } ], "thesis_advisor": [ { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Spacecraft observations must be calibrated absolutely in order to investigate the photometric properties of the Martian surface and atmosphere. The accuracy of the Mariner 9 and Viking Orbiter television system calibration was evaluated by comparing the two data sets with each other and with Earth-based spectrophotometry of Mars and Phobos. The Viking imaging data are consistent with published estimates of the geometric albedo of Phobos, which is uncertain by about 20%. Mariner 9 data are calibrated to within about \u00b120% by comparing Phobos images with Viking data. Better photometric observations of Phobos are necessary to improve the calibration of the Viking Orbiter and Mariner 9 television systems. Similarly, inflight Phobos observations should be used to calibrate imaging systems on future Mars missions.
\r\n\r\nMariner 9 images were processed for comparison with nearly simultaneous infrared spectra of the south polar cap of Mars recorded in 1971-72. Combined analysis of these observations indicates that the southern residual cap was covered by carbon dioxide frost throughout the summer, in agreement with Viking Orbiter measurements made three Mars years later. Thermal modeling of the spectra shows that areas of intermediate albedo are cooled to the sublimation temperature of CO2, suggesting that frost is present but not visible. Topographic roughness may shade the CO2 from the sun and produce the variegated appearance of the residual cap.
\r\n\r\nFive color/albedo units, including polar frost, have been recognized and mapped in the southern layered deposits on Mars. Atmospheric dust scattering was measured in shadows and modeled in order to remove the component of brightness due to the atmosphere and quantify the albedo and color of the surface. The layered deposits appear to be mantled by red dust, except where eolian stripping has exposed the underlying bedrock. Frost and bare ground are mixed below the resolution of the images in many areas adjacent to the polar cap, some of which appear to be younger than the surrounding layered terrain. Dark material has been deposited in topographic depressions in much of the south polar region, including the layered deposits. The available observational data suggest that the layered deposits are composed of bright dust, ice, and a small amount of dark material. If the dark material is sand, a periodic change in polar winds seems required in order to transport the sand poleward into the layered terrain. In any case, the observations are not consistent with the layered deposits being composed only of bright dust and ice.
\r\n\r\nMaximum slopes of 10-20 degrees occur on an exposure of layered deposits within the south polar residual cap of Mars. A new photoclinometric technique is used to produce profiles of slope and albedo using high resolution Mariner 9 images. Stereophotogrammetry is also used to constrain the photoclinometric solutions, which resolve layer thicknesses of 100-300 meters. The results are limited by the ~200 meter resolution of the images, and thinner (unresolved) layers are likely. The ~25% maximum albedo variations are correlated with slope, indicating that frost is present on level areas. There is evidence for temporal changes in frost distribution in the 7 days (4\u00b0 of Ls) between the two images used in this study, demonstrating that future photoclinometric studies of the polar regions must be attempted carefully. The magnitude of the slopes derived here suggest that the layers are competent, perhaps due to the presence of a weathering rind.
\r\n\r\nWeathering of the layered deposits by sublimation of water ice can account for the data presented here and previous observations of the north polar deposits. The non-volatile component of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust or sand. Deposition of sand in the layered deposits is problematical, so inclusion of dark dust is preferred. The dark dust may be similar to the magnetic material found at the Viking Lander sites, and may therefore preferentially form ~ 100\u00b5 filamentary residue particles upon weathering. Once eroded from the layered deposits, these particles may then saltate to form the dark sand dunes found in both polar regions. Eventual destruction of the particles could allow recycling of the dark dust into the layered deposits via atmospheric suspension.
", "doi": "10.7907/bty4-vk56", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:2759", "collection": "thesis", "collection_id": "2759", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06282007-082748", "primary_object_url": { "basename": "maher-ka_1989 .pdf", "content": "final", "filesize": 18356906, "license": "other", "mime_type": "application/pdf", "url": "/2759/43/maher-ka_1989 .pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Geology of the Jackson Mountains, Northwest Nevada", "author": [ { "family_name": "Maher", "given_name": "Kevin A.", "clpid": "Maher-Kevin-A" } ], "thesis_advisor": [ { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" } ], "thesis_committee": [ { "family_name": "Silver", "given_name": "Leon T.", "clpid": "Silver-L-T" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Saleeby", "given_name": "Jason B.", "clpid": "Saleeby-J-B" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Jackson Mountains are located in the western Great Basin in Humboldt County, northwest Nevada. The range contains a late Paleozoic to Mesozoic depositional sequence. This sequence records sedimentation, volcanism and deformation in a back-arc setting. The Mississippian to late Early Permian McGill Canyon Formation was deposited in basinal to slope to distal shelf environments, dominated by hemipelagic and turbiditic facies. In the Permian there was an volcanic arc andesite component, and a nearby contemporaneous carbonate platform shed olistostromes into the unit. The McGill Canyon was laid down in an area between the McCloud arc and the Havallah back-arc basin. The late Middle Triassic to middle Norian Bliss Canyon Formation was laid down in basinal to fore-reef to carbonate platform to lagoonal to terrigenous littoral environments. Both of these formations are of flap sequences deposited on an east-facing, back-arc margin. The Bliss Canyon represents the western margin of the Early Mesozoic marine basin of the western Great Basin. From the late Norian to the Bathonian, several stages of subearial volcanism and alluvial epiclastic sedimentation laid down the Happy Creek Formation, a thick arc andesite volcanic pile. The Happy Creek is part of the Early Mesozoic Cordilleran magmatic arc province. In the Bathonian, this volcanic pile was cut by a conjugate sinistral high-angle wrench fault system as volcanism waned. During the Callovian, sediments of the King Lear Formation filled in and then overlapped the wrench basins. These sediments were derived from the east, where a west-vergent thrust system was active. This phase of thrusting ceased by the Oxfordian. Arc-related silicic volcanism and alluvial to fluvial sedimentation within the King Tear continued into the Aptian, when the thrusts were reactivated during a second phase. Both phases of thrusting verged both east and west. Stocks, dikes and sills of the Early Mesozoic Intrusive suite are comagmatic with the volcanism in the Happy Creek and King Lear, and intrude the sedimentary units. This suite both plugs and is truncated by the wrench faults and the first phase of thrusting, but is cut by the second phase. The Jackson Mountains are part of the Black Rock terrane in northwest Nevada. Within this terrane, the rocks share a common tectonic history and stratigraphy distinct from the neighboring terranes, and are separated from them by Mesozoic thrust and strike-slip faults.
", "doi": "10.7907/DE6N-4051", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:4554", "collection": "thesis", "collection_id": "4554", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11142006-131417", "primary_object_url": { "basename": "Kirk_rl_1987.pdf", "content": "final", "filesize": 17917757, "license": "other", "mime_type": "application/pdf", "url": "/4554/1/Kirk_rl_1987.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Thermal Evolution of Ganymede and Implications for Surface Features. II. Magnetohydrodynamic Constraints on Deep Zonal Flow in the Giant Planets. III. A Fast Finite-Element Algorithm for Two-Dimensional Photoclinometry", "author": [ { "family_name": "Kirk", "given_name": "Randolph Livingstone", "clpid": "Kirk-Randolph-Livingstone" } ], "thesis_advisor": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" } ], "thesis_committee": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "The work is divided into three independent papers:
\r\n\r\nPAPER I:
\r\n\r\nThermal evolution models are presented for Ganymede, assuming a mostly differentiated initial state of a water ocean overlying a rock layer. The only heat sources are assumed to be primordial heat (provided by accretion) and the long-lived radiogenic heat sources in the rock component. As Ganymede cools, the ocean thins, and two ice layers develop, one above composed of ice I, and the other below composed of high-pressure polymorphs of ice. Subsolidus convection proceeds separately in each ice layer, its transport of heat calculated using a simple parameterized convection scheme and the most recent data on ice rheology. The model requires that the average entropy of the deep ice layer exceed that of the ice I layer. If the residual ocean separating these layers becomes thin enough, then a Rayleigh-Taylor-like (\"diapiric\") instability may ensue, driven by the greater entropy of the deeper ice and merging the two ice mantles into a single convective layer. This instability is not predicted by linear analysis but occurs for plausible finite amplitude perturbations associated with large Rayleigh number convection. The resulting warm ice diapirs may lead to a dramatic \"heat pulse\" at the surface and to fracturing of the lithosphere, and may be directly or indirectly responsible for resurfacing and grooved terrain formation on Ganymede. The timing of this event depends rather sensitively on poorly known rheological parameters but could be consistent with chronologies deduced from estimated cratering rates. Irrespective of the occurrence or importance of the heat pulse, we find that lithospheric fracturing requires rapid stress loading (on a timescale \u227e 104) years). Such a timescale can be realized by warm ice diapirism, but not directly by gradual global expansion. In the absence of any quantitative and self-consistent model for the resurfacing of Ganymede by liquid water, we favor resurfacing by warm ice flows,which we demonstrate to be physically possible, a plausible consequence of our models, compatible with existing observations, and a hypothesis testable by Galileo. We discuss core formation as an alternative driver for resurfacing, and conclude that it is less attractive. We also consider anew the puzzle of why Callisto differs so greatly from Ganymede, offering several possible explanations. The models presented do not provide a compelling explanation for all aspects of Ganymedean geological evolution, since we have identified several potential problems, most notably the apparently extended period of grooved terrain formation (several hundred million years), which is difficult to reconcile with the heat pulse phenomenon.
\r\n\r\nPAPER II:
\r\n\r\nThe observed zonal flows of the giant planets will, if they penetrate below the visible atmosphere, interact significantly with the planetary magnetic field outside the metalized core. The appropriate measure of this interaction is the Chandrasekhar number Q = (H2)/(4\u03c0\u03c1\u03bd\u03b12\u03bb) (where H = radial component of the magnetic field, \u03bd = eddy viscosity, \u03bb = magnetic diffusivity, \u03b1-1 = lengthscale on which \u03bb varies); at depths where Q \u2273 1 the velocity will be forced to oscillate on a small lengthscale or decay to zero. We estimate the conductivity due to semiconduction in H2 (Jupiter, Saturn) and ionization in H2O (Uranus, Neptune) as a function of depth; the value \u03bb \u2243 1010 cm2s-1 needed for Q = 1 is readily obtained well outside the metallic core (where \u03bb \u2243 102 cm2s-1).
\r\n\r\nThese assertions are quantified by a simple model of the equatorial zonal jet in which the flow is assumed uniform on cylinders concentric with the spin axis, and the viscous and magnetic torques on each cylinder are balanced. We solve this \"Taylor constraint\" simultaneously with the dynamo equation to obtain the velocity and magnetic field in the equatorial plane. With this model we reproduce the widely differing jet widths of Jupiter and Saturn (though not the flow at very high or low latitudes) using \u03bd = 2500 cm2s-1, consistent with the requirement that viscous dissipation not exceed the specific luminosity. A model Uranian jet consistent with the limited Voyager data can also be constructed, with appropriately smaller \u03bd, but only if one assumes a two-layer interior. We tentatively predict a wide Neptunian jet.
\r\n\r\nFor Saturn (but not Jupiter or Uranus) the model has a large magnetic Reynolds number where Q = 1 and hence exhibits substantial axisymmetrization of the field in the equatorial plane. This effect may or may not persist at higher latitudes. The one-dimensional model presented is only a first step. Variation of the velocity and magnetic field parallel to the spin axis must be modeled in order to answer several important questions, including: 1) What is the behavior of flows at high latitudes, whose Taylor cylinders are interrupted by the region with Q \u2273 1? 2) To what extent is differential rotation in the envelope responsible for the spin-axisymmetry of Saturn's magnetic field?
\r\n\r\nPAPER III:
\r\n\r\nIt is shown that the problem of two-dimensional photoclinometry (PC) -- the reconstruction of a surface z(x,y) from a brightness image B(x,y) -- may be formulated in a natural way in terms of finite elements. The resulting system of equations is underdetermined as a consequence of the lack of boundary conditions for z, but a unique solution may be chosen by minimizing a function S expressing the \"roughness\" of the surface. An efficient PC algorithm based on this formulation is presented, requiring ~ 10.66 (four-byte) memory locations and ~104 floating multiplications/additions per pixel, and incorporating: 1) Minimization of the roughness by the penalty method, which yields the smallest set of equations. 2) Iterative solution of the nonlinear equations by Newton's method. 3) Solution of the linearized equations by an inner iterative cycle of successive over-relaxation, which takes advantage of the extreme sparseness of the system. 4) Multigridding, in which the solutions to the smaller problems obtained by reducing the resolution are used recursively to greatly speed convergence at the higher resolutions, and 5) A rapid noniterative initial estimate of z obtained by exploiting the special symmetry of the equations obtained in the first linearization.
\r\n\r\nThe algorithm is extensively demonstrated on 200 by 200 pixel synthetic \"images\" generated from digital topographic data for northern Utah over a range of phase angles. Rms error in the solution is ~ 22 m, out of ~ 660 m total relief. The error is dominated by \"stripes\" with the same azimuth as the light source, resulting from use of the roughness criterion in lieu of boundary conditions; the rms error along profiles parallel to the stripes is only ~ 2-8 m, depending on the phase angle. Satisfactory solutions are obtained even in the presence of quantization error, noise, and moderate blur in the image.
\r\n\r\nApplications of the PC algorithm to both remote sensing and photomicrography are sketched; a photoclinometric map of a low-relief Precambrian era fossil is presented as an example of the latter. Prospects for dealing with photometrically inhomogeneous surfaces, and an extension of the method to the analysis of side-looking radar data (\"radarclinometry\") are also discussed.
", "doi": "10.7907/T5PT-S948", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:7484", "collection": "thesis", "collection_id": "7484", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02202013-103037890", "primary_object_url": { "basename": "Rudy 1987.pdf", "content": "final", "filesize": 28898031, "license": "other", "mime_type": "application/pdf", "url": "/7484/1/Rudy 1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mars: High Resolution VLA Observations at Wavelengths of 2 and 6 cm and Derived Properties", "author": [ { "family_name": "Rudy", "given_name": "Donald James", "clpid": "Rudy-Donald-James" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" } ], "thesis_committee": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Observations of Mars at wavelengths of 2 and 6cm were made using the VLA in its A configuration. Two seasons were observed; late spring in the northern hemisphere (LS ~ 60\u00b0) and early summer in the southern summer (LS ~ 300\u00b0). The sub-earth latitudes were 25\u00b0N and 25\u00b0S, for each of these seasons respectively. So the geometry for viewing the polar region was optimal in each case. Whole-disk brightness temperatures were estimated to be 193.2 K \u00b1 1.0 at 2 cm and 191.2 K \u00b1 0.6 at 6 cm for the northern data set and 202.2 K \u00b1 l.0 at 2 cm and 195.4 K \u00b1 0.6 at 6 cm for the southern data set (formal errors only). Since measurements of the polarized flux were taken at the same time, whole-disk effective dielectric constants could be estimated and from these, estimates of sub-surface densities could be made. The results of these calculations at 2cm yielded whole-disk effective dielectric constants of 2.34 \u00b1 0.05 and 2.02 \u00b1 0.03 which imply sub-surface densities of 1.24 g cm-3 \u00b1 0.06 and 1.02 g cm-3 \u00b1 0.05 for the north and south, respectively. The same calculations at 6 cm yielded effective densities of 1.45 g cm-3 \u00b1 0.10 and 1.31 g cm-3 \u00b1 0.07 from effective dielectric constants of 2.70 \u00b1 0.09 and 2.48 \u00b1 0.06 for the north and south data sets, respectively.
\r\n\r\nFrom the mapped data these parameters were also estimated as a function of latitude between latitudes of 15\u00b0S and 60\u00b0N for the north data set; and between latitudes of 30\u00b0N and 60\u00b0S for the south data set. A region in which the brightness temperature behaves in an anomalous manner was discovered in both data sets. This region lies between about 10\u00b0S and 40\u00b0S. Here the brightness temperatures at both wavelengths in both data sets appears lower, by 4 K to 8 K, than a nominal model would predict. In addition to the effective dielectric constant and sub-surface density the radio absorption length of the sub-surface was estimated. The radio absorption length for most of these latitudes was about 15 wavelengths with formal errors on the order of 5 or 10 wavelengths. This is true for both data sets. The estimation of the effective dielectric constant at most latitudes was between 2 and 3.5 with only slight differences between the two different wavelengths. The two data sets show the same relative trends, but are off by a scaling factor.
\r\n\r\nThese estimates of the dielectric constant lead to estimation of the sub-surface densities as a function of latitude. Most calculations of the sub-surface density yielded results between 1 and 2 g cm-3 with errors on the order of 0.5 g cm-3. These results seem to imply that the sub-surface is not much different than the surface as observed by the Viking and Mariner missions. In line with this, an examination of the correlation of the dielectric constant at each wavelength with the thermal inertia, determined by the Viking infrared measurements, shows a relatively strong correlation, at both wavelengths, for the North data set. The South data set, however, shows little to nocorrelation between the radio parameters and the thermal inertia. Since the South data set is primarily composed of latitudes which contain the anomalous region, it is not suprising that the South data set shows no correlation.
\r\n\r\nIn addition, the thermal-radiative model used to estimate the above parameters was used to estimate the variability of the whole-disk brightness temperature of Mars. This was done in an effort to establish a background for those astronomers wishing to use Mars as a calibration source. The parameters investigated for their effect on the whole-disk brightness temperature of Mars were: the sub-earth longitude, the sub-earth latitude, the sub-earth time of day, the dielectric constant, and the radio absorption length. A nominal model was first created which established the variation of the brightness temperature as a function of season and radio absorption length. A nominal value of 2.2 was used for the dielectric constant, and the sub-earth latitude was set at 0\u00b0N and the sub-earth longitude was set at 75\u00b0W. The sub-earth time of day was held at noon for this nominal model. This is equivalent to a 0\u00b0 phase angle. The most important geometric factor was the sub-earth latitude. The error in estimating the whole-disk brightness temperature of Mars by using the wrong sub-earth latitude can be as large as 5 to 10%. The charts presented will be useful to estimate the whole-disk brightness temperature which the thermal model would predict. It is believed that the error in this estimate is less than or equal to 5 K.
\r\n", "doi": "10.7907/3g59-p796", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:5720", "collection": "thesis", "collection_id": "5720", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04162010-092926816", "primary_object_url": { "basename": "Paige_da_1985.pdf", "content": "final", "filesize": 7612070, "license": "other", "mime_type": "application/pdf", "url": "/5720/1/Paige_da_1985.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Annual Heat Balance of the Martian Polar Caps from Viking Observations", "author": [ { "family_name": "Paige", "given_name": "David Abbey, Jr.", "orcid": "0009-0001-6122-9904", "clpid": "Paige-David-Abbey-Jr" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Zurek", "given_name": "Richard W.", "clpid": "Zurek-Richard-W" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis presents the first measurements of the annual heat budgets of the polar caps of Mars from spacecraft observations. The primary motivation for this work is to understand why seasonal CO2 frost deposits at the north pole of Mars disappear in the summer, whereas seasonal CO2 deposits near the south pole do not. This behavior is not expected to first order because both Martian poles receive the same total amount of sunlight at the top of the atmosphere over the course of a year. Understanding why the Martian north and south polar caps behave in an asymmetric fashion is important because the vapor pressures of permanent polar CO2 deposits determine the planet-wide surface pressures of CO2 gas, which is the dominant constituent of the Martian atmosphere.
\r\n\r\nAnnual radiation budgets for the core regions of the north and south polar caps are determined from solar reflectance and infrared emission observations obtained by the Infrared Thermal Mappers (IRTMs) aboard the two Viking orbiters. The results show that the absence of CO2 frost at the north pole during summer is primarily due to an asymmetry in the rates of CO2 frost sublimation at surface in the north and south during spring. Further analysis traces this difference to seasonal frost reflectivities being approximately 20% lower in the north than in the south during late spring. It is shown that seasonal frost deposits at the poles demonstrate a remarkable tendency to not become darker when contaminated with dust, and to become brighter with increasing rates of solar illumination. Since peak solar illumination rates are presently higher at the south pole than the north pole because of the large eccentricity of Mars' orbit, the tendency for the frost to become brighter with increasing rates of solar illumination explains the asymmetry. The tendency for the frost to not become darker when contaminated by dust explains why the seasonal behavior of the Martian polar caps is highly repeatable from year to year despite interannual variations in the occurrence of Martian global dust storms.
\r\n\r\nIt is suggested that the unexpected properties of Martian seasonal frost deposits revealed by the results of this study are caused by the tendency for dust particles within the frost to absorb solar radiation, sublimate the solid CO2 that supports them and sink into the frost. If the current behavior of Martian CO2 frost is an indicator to past events, then interactions between dust and frost have exerted a powerful stabilizing influence on the Martian climate system.
", "doi": "10.7907/DPB3-P589", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:7466", "collection": "thesis", "collection_id": "7466", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02062013-144652620", "primary_object_url": { "basename": "Jakosky_bm_1983.pdf", "content": "final", "filesize": 41355084, "license": "other", "mime_type": "application/pdf", "url": "/7466/1/Jakosky_bm_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Seasonal Behavior of Water Vapor in the Mars Atmosphere", "author": [ { "family_name": "Jakosky", "given_name": "Bruce Martin", "orcid": "0000-0002-0758-9976", "clpid": "Jakosky-Bruce-Martin" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" } ], "thesis_committee": [ { "family_name": "Muhleman", "given_name": "Duane Owen", "clpid": "Muhleman-D-O" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Farmer", "given_name": "C. Bernard", "clpid": "Farmer-C-Bernard" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Understanding the evolution of volatiles on Mars requires understanding the processes which are currently acting to cause exchange between the various reservoirs on annual and longer timescales. On the seasonal timescale, exchange of water can occur between the atmosphere and reservoirs of ice in the polar caps and of adsorbed water in the near-surface regolith covering the remainder of the planet. This exchange is driven by the seasonally-varying insolation and its consequent effects on the surface and subsurface temperatures and on the advance and retreat of the predominantly-CO2 polar caps. On a longer timescale, exchange can occur between these same reservoirs, and is driven by the changing annual insolation patterns which result from the 105-year timescale variations in Mars' orbital elements (predominantly the orbital obliquity). Observations of the seasonal water cycle and its variations from year to year from the Viking spacecraft and from Earth provide clues as to the importance of the various reservoirs and provide boundary conditions against which models of the various processes can be compared.
\r\n\r\nThe water vapor content of the Mars atmosphere was measured from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) for a period of more than one Martian year, from June, 1976, through April. 1979, and the results are presented here. The data reduction incorporates spatial and seasonal variations in surface pressure, and supplements earlier published versions of less-complete data. Column abundances vary between zero and about 100 precipitable microns (pr \u00b5m), depending on location and season, while the entire global abundance varies seasonally between an equivalent of about 1 and 2 km3 of ice. The first appearance of vapor at non-polar latitudes as northern summer approaches, and the drop in abundance at mid-latitudes as summer ends, both strongly imply the existence of a seasonal reservoir for water within the regolith. There appear to be no net annual sources away from the poles that contribute significant amounts of water. However, the strong annual gradient of vapor from north to south implies a net annual flow of vapor toward the south; this southward flow may be balanced in part by a northward flow during the global dust storms, by transport in the form of clouds or adsorbed onto dust grains, or during other years. The perennially-cold nature of the south-polar residual cap, along with the relatively large summertime vapor abundances over the cap, implies a net annual condensation of vapor onto the cap. Estimates are made of the southward transport, and are consistent with the movement of ice being important in the formation and evolution of the polar layered terrain, and with the formation of the individual layers at the rate of one per obliquity cycle (105 years).
\r\n\r\nThe global distribution of the annual average abundance of vapor is found to correlate well with Martian topography, as might be expected for a uniform constant atmospheric mixing ratio. If this topographic effect is divided out, the resulting residual map correlates with maps of surface albedo and thermal inertia; this correlation may be related to the control exerted by the surface and subsurface temperatures on the adsorption/desorption process and on the atmospheric temperature profile and, hence, the vapor holding capacity of the atmosphere.
\r\n\r\nThe vertical distribution of vapor within the atmosphere is inferred through comparison of the observed water vapor abundances with measurements of atmospheric temperatures. In order to not saturate, the vapor must be confined to the lowermost 1 to 3 scale heights (~ 10-30 km), with this height varying with location and season. Near-surface water vapor can condense out overnight and form a morning fog; estimates of the optical thickness of the resulting fog are made, and they agree well with observations of diurnal variations of opacity due to fog formation.
\r\n\r\nPrevious Earth-based near-infrared observations are re-interpreted here; they show that water ice condenses out onto the seasonal polar caps, but not during midday near the equator. Earth-based observations of the vapor column abundance are compared with the Viking MAWD results, and indicate that the seasonal cycle shows a remarkable repeatability, except during 1969 when large vapor abundances were present during southern summer. This difference is explained by postulating that all of the CO2 had sublimed off of the south residual cap that year, exposing the underlying water cap which would subsequently sublime and produce large amounts of atmospheric vapor; the rate and amount of CO2 sublimation may depend on the degree of dust storm activity each year and hence on the different thermal loads placed on the cap.
\r\n\r\nThe possible processes for producing seasonal changes in the atmospheric vapor abundances have been modeled in order to infer the relative importance of each process in the seasonal cycle. The equilibrium between water vapor and water adsorbed onto the regolith grains is sufficiently temperature-dependent that seasonal surface temperature variations are capable of driving a large exchange of water between the atmosphere and subsurface. For the likely range of regolith properties, this exchange is found to be from 10-150% of the observed seasonal change in atmospheric abundance; the differences between this exchange and the observed behavior result from transport of vapor due to the atmospheric circulation. Due to the latitudinal gradient of atmospheric vapor, there will also be a gradient of adsorbed water, with the south regolith containing much less water than that in the north; this gradient in the regolith will result independent of the vapor diffusivity in the regolith, as the near-surface water will be able to equilibrate on some timescale.
\r\n\r\nModels have been constructed which include regolith exchange, polar cap formation, and atmospheric transport. Comparison of the model results with the vapor observations and with other data regarding the physical nature of the surface allows constraints to be placed on the relative importance of each process. The models are capable of satisfactorily explaining the gross features of the observed behavior using plausible values for the regolith and atmosphere mixing terms. In the region between the polar caps, the regolith contributes as much water to the seasonal cycle of vapor as does transport in from the more-poleward regions, to within a factor of two. Globally, 10-50% of the seasonal cycle of vapor results from exchange of water with the regolith, about 40% results from the behavior of the residual caps, and the remainder is due to exchange of water with the seasonal caps. It is difficult to determine the relative importance of the processes more precisely than this because both regolith and polar cap exchange of water act in the same direction, producing the largest vapor abundance during the local summer. The system is ultimately regulated on the seasonal timescale by the polar caps, as the time to reach equilibrium between the atmosphere and regolith or between the polar atmosphere and the global atmosphere is much longer than the time for the polar caps to equilibrate with the local atmosphere. This same behavior will bold for longer timescales, with the polar caps being in equilibrium with the insolation as it changes on the obliquity timescale, and the atmosphere and regolith following along.
", "doi": "10.7907/f9fz-gg50", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:4566", "collection": "thesis", "collection_id": "4566", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11152004-162115", "type": "thesis", "title": "The Luminescent Solar Concentrator", "author": [ { "family_name": "Batchelder", "given_name": "John Samuel", "clpid": "Batchelder-John-Samuel" } ], "thesis_advisor": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" } ], "thesis_committee": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Luminescent Solar Concentrator (LSC) allows sunlight to be concentrated through the use of light pipe trapping of luminescence. Such concentrators do not require tracking, and they can reduce the cost of solar energy conversion by reducing the required area of photovoltaic cells. We have conducted the following experimental and theoretical investigations in order to optimize the LSC's performance.
\r\n\r\nThe spectral characteristics of 18 organic laser dyes are studied for their applicability as luminescing centers. The spectral homogeneity and self-absorption characteristics of representative dyes are examined in detail. The relative spectral homogeneity of such dyes is shown to depend upon the surrounding material using narrow band laser excitation. We develop three independent techniques for measuring self-absorption rates; these are time-resolved emission, steady state polarization anisotropy, and spectral convolution. Prototype devices are tested for performance, and the componant dyes are tested for stability to solar exposure.
\r\n\r\nA model is developed which predicts the efficiency and gain of and LSC from the spectroscopic characteristics of its components. A critical optical density (CODE) is assigned to the dyes surveyed which predicts the self-absorption limited performance for a particular dye. The maximum efficiency of an LSC is found using a simple model and the experimentally measured Stokes shift required to minimize self-absorption.
\r\n\r\nWe find that the performance of LSCs which achieve high light concentration is primarily limited by self-absorption and by photodegradation. The maximum efficiency possible is about 9% in such systems, and present devices can achieve about 3%. A typical lifetime for an LSC using organic laser dyes due to photodegradation is on the order of a month.
", "doi": "10.7907/W5W7-9660", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:4399", "collection": "thesis", "collection_id": "4399", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11042002-153232", "primary_object_url": { "basename": "Watson_k_1964.pdf", "content": "final", "filesize": 4070255, "license": "other", "mime_type": "application/pdf", "url": "/4399/1/Watson_k_1964.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. The Thermal Conductivity Measurements of Selected Silicate Powders in Vacuum from 150\u00b0 to 350\u00b0 K. II. An Interpretation of the Moon's Eclipse and Lunation Cooling as Observed through the Earth's Atmosphere from 8-14 Microns", "author": [ { "family_name": "Watson", "given_name": "Kenneth", "clpid": "Watson-Kenneth" } ], "thesis_advisor": [ { "family_name": "Brown", "given_name": "Harrison", "clpid": "Brown-Harrison" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Press", "given_name": "Frank", "clpid": "Press-F" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Brown", "given_name": "Harrison", "clpid": "Brown-Harrison" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "An apparatus was constructed to measure the thermal conductivity of powders in vacuum from 150\u00b0 to 350\u00b0K. It was found that the conductivity of selected silicate powders can be adequately represented, within the experimental errors, by a temperature independent term related to the contact conduction plus a temperature cube term which is due to radiative transfer between and through the grains. The conductivity for glass spheres approximately suggests an inverse grain size dependence and does not appear to be related in any simple manner to the elastic contact area between the spheres. The effects of angular grains, produced by crushing, and limited chemical composition range are not significant when compared with the experimental errors. The radiative transfer term which is grossly independent of chemical composition and grain texture is dominated by radiation between the grains for grain sizes > 300 \u03bc. Radiation through the grains is significant for grain sizes < 100 \u03bc.
\r\n\r\nPrevious interpretations of the eclipse observations of Pettit and Nicholson indicate that homogeneous constant thermal property models provide an adequate fit. The recent lunation observations of Murray and Wildey cannot be adequately explained by homogeneous models with either constant thermal properties or with thermal properties which are based on the results of this experimental investigation and existing specific heat data. It is suggested that the possibility of layering can best be examined in the region of the morning terminator.
\r\n", "doi": "10.7907/7HDE-1M52", "publication_date": "1964", "thesis_type": "phd", "thesis_year": "1964" } ]