This thesis consists of two independent papers:
\r\n\r\nPAPER I:
\r\n\r\nThe spectral reflectance of elemental sulfur is examined in a set of laboratory experiments to determine the factors that affect the transformation rate of monoclinic (\u03b2) sulfur and various other sulfur allotropes into orthorhombic (\u03b1) sulfur. The laboratory data have implications for the spectral variation and physical behavior of freshly solidified sulfur, if any exists, on Jupiter's satellite Io. Depending on its thermal history, molten sulfur on Io would initially solidify into a glassy solid or a monoclinic crystalline lattice; these forms might contain polymeric sulfur molecules as well as the more abundant S8 molecules. If freshly frozen sulfur on Io could lose heat rapidly and approach ambient dayside Io temperatures within several hours, then some of the metastable sulfur allotropes could be maintained on Io virtually indefinitely. Small droplets of sulfur ejected during plume eruptions might cool quickly enough to preserve these allotropes, but sulfur in large volcanic flows or lakes would probably remain warm long enough for phase transformations to proceed at a visible rate.
\r\n\r\nPAPER II:
\r\n\r\nPhotodissociation of methane at high levels in Neptune's atmosphere leads to the production of more complex hydrocarbon species such as ethane, acetylene, methylacetylene, propane, diacetylene, ethylacetylene, and butane. These gases diffuse to the lower stratosphere where temperatures are low enough to allow all seven of the aforementioned species to condense. Particle formation may not occur readily, however, as the vapor species become supersaturated. We present a theoretical analysis of particle formation mechanisms at conditions relevant to Neptune's troposphere and stratosphere and show that hydrocarbon nucleation is very inefficient under Neptunian conditions: saturation ratios much greater than unity are required for aerosol formation by either heterogeneous, ion-induced, or homogeneous nucleation. Thus, stratospheric hazes may form far below their saturation levels. We compare nucleation models with detailed atmospheric photochemical models in order to place realistic constraints on the altitude levels at which we expect hydrocarbon hazes or clouds to form on Neptune.
\r\n", "doi": "10.7907/S8F2-V423", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:16806", "collection": "thesis", "collection_id": "16806", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10212024-225714489", "primary_object_url": { "basename": "Diner_DJ_1978.pdf", "content": "final", "filesize": 60123682, "license": "other", "mime_type": "application/pdf", "url": "/16806/1/Diner_DJ_1978.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Silicon Vidicon Imaging of Jupiter 4100-8300\u00c5: Spectral Reflectivity, Limb-Darkening, and Atmospheric Structure. II. Simultaneous Ultraviolet (0.36 \u00b5m) and Infrared (8-20 \u00b5m) Imaging of Venus: Properties of Clouds in the Upper Atmosphere", "author": [ { "family_name": "Diner", "given_name": "David Joseph", "clpid": "Diner-David-Joseph" } ], "thesis_advisor": [ { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Part 1 presents the results of high spatial resolution area photometry of Jupiter in six continuum wavelength channels from 4100-8300\u00c5. Spectral reflectivity and limb-darkening data in belts and zones are fitted by a simple semi-infinite homogeneous scattering model which provides a convenient parameterization of the results, as well as a determination of the spectral and spatial variations in the continuum single scattering albedo and information regarding the shape of the single scattering phase functions. It is found that belts are generally more backscattering than zones, particularly in the blue, and there is a trend toward increased forward scattering\r\nat longer wavelengths. The numerical results are compared to earlier ground-based observations of jovian limb-darkening (Harris, 1961; Binder and McCarthy, 1973; Pilcher and Kunkle, 1976) and significant disagreement is found in some cases, Extrapolations of the limb\u00ad darkening data to 12\u00b0 phase angle are compared with the results of the Pioneer 10-imaging photopolarimeter (IPP) experiment (Tomasko et al., 1976). Although there is quantitative disagreement between the vidicon results and the IPP data, the ground-based and Pioneer 10 results show the same relative spectral and regional trends in the shape of the limb structure profiles from the blue to the red and between a belt and a zone. The limb-darkening profiles are also com\u00ad pared to models derived from measurements of the spatial distribution of equivalent width of the H\u2082 4-0 S(1) quadrupole line (Cochran, 1976). It is found that these models fare reasonably well in the South Tropical Zone but are much too limb-darkened relative to the data in the North Equatorial Belt. A discussion of the possible causes of the differences between the vidicon data and other ground\u00ad based, Pioneer 10, and spectroscopic results is presented.
\r\n\r\nSome numerical examples of limb-darkening expected from simple models are presented. In particular, the effects of Rayleigh scat\u00adtering, either by a fine, colored dust, or by the gaseous atmosphere on the spectral characteristics of limb-darkening are investigated. It is found that the observed backscattering may be explained by a combination of molecular scattering and scattering by small dust particles, and the increased forward scattering in the red arises from the \u03bb\u207b\u2074 dependence of Rayleigh scattering optical depth and inclusion of forward scattering cloud particles. Such a model works reasonably well in the North Equatorial Belt, but predicts a spectral variation in limb-darkening that is greater than the observations imply for the South Tropical Zone.
\r\n\r\nPart 2 discusses high spatial resolution images of Venus which were obtained in the 0.36 \u00b5m and 8-20 \u00b5m spectral regions throughout the 1974, 1975, and 1977 apparitions. The observing system, method of image acquisition, and data reduction and processing techniques are presented along with a discussion of the spectral, temporal, and spatial characteristics of the infrared and ultraviolet flux from the planet, The infrared data are compared with previous ground\u00ad based results obtained at lower spatial and spectral resolution (Sinton and Strong, 1960; Murray et al., 1963; Westphal et al., 1965; Ingersoll and Orton, 1974) and Venera 9 and 10 infrared radio\u00ad meter results (Ksanfomality et al., 1976).
\r\n\r\nDay-night contrasts in equatorial infrared flux were observed in images in which the evening and morning terminators were near the central meridian. A systematic increase in 8-14 \u00b5m flux associated with the emergence of the atmosphere from daylight into evening was observed, and is shown to exhibit significant day-to-day variability, The data also show that the daytime side of the morning terminator is warmer than the dark side, but this night-day asymmetry is system\u00adatically smaller than the day-night brightening seen in the Venus evening.
\r\n\r\nSouth and north infrared polar anomalies similar to the one observed near the Venus south pole by Murray et al, (1963) have been observed during the 1974 and 1975 apparitions, respectively. The ob\u00adservations indicate that the feature is most prominent between Venus midnight and dawn.
\r\n\r\nThe infrared limb-darkening in the equatorial and polar direc\u00adtions are compared and it is seen that the magnitude and spectral variation of the polar darkening are in general greater than the equatorial darkening. The magnitude of the equatorial darkening is consistent with a temperature lapse rate of roughly -3\u00b0K/km, assuming a model in which aerosol is distributed exponentially and mixed homogeneously with the atmospheric gas.
\r\n\r\nEvidence for a correlation between features observed in simul\u00adtaneous infrared (8-14 \u00b5m) and ultraviolet (0.36 \u00b5m) images has been found. The sense of the correlation is such that bright UV markings correspond to bright (warm) IR features, and similarly, dark UV markings correspond to dark (cool) IR features. This result implies that dark UV clouds are higher or denser than the bright regions.
", "doi": "10.7907/r1rr-5q90", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:5707", "collection": "thesis", "collection_id": "5707", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04082010-091644952", "primary_object_url": { "basename": "Terrile_rj_1978.pdf", "content": "final", "filesize": 11435423, "license": "other", "mime_type": "application/pdf", "url": "/5707/1/Terrile_rj_1978.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "High Spatial Resolution Infrared Imaging of Jupiter: Implications for the Vertical Cloud Structure from Five-Micron Measurements", "author": [ { "family_name": "Terrile", "given_name": "Richard John", "clpid": "Terrile-Richard-John" } ], "thesis_advisor": [ { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This study describes the design and construction of a 5 \u00b5m imaging system used at the Hale 5 m (200 inch) telescope to acquire high spatial resolution infrared images of Jupiter. These images, recorded in a spectral region clear of terrestrial and Jovian gaseous absorption, offer a unique look into the deep atmosphere and provide direct observational evidence for the existence of multiple layers of clouds in the Jovian atmosphere. Evidence of layering is provided by the observed trimodal nature and persistence of the 5 \u00b5m flux-frequency distribution of equal areas on the Jovian disk. This indicates that three distinct brightness temperatures have a higher probability of being observed than a continuum of temperatures, and that, despite \r\nsignificant observed variations in the lateral 5 \u00b5m cloud distribution, this phenomenon is a long term stable vertical cloud feature. Furthermore, the visible color differences correlate with areas of different\r\n5 \u00b5m intensity, implying that the colors are due to reflection from areas of different chemistry or state at different levels in the atmosphere. Also, short time scales are observed for large 5 \u00b5m flux variations over extensive areas of the Jovian disk, supporting the concept \r\nthat the redistribution of obscuring clouds accounts for the contrasts at 5 \u00b5m. Finally, the 5 \u00b5m limb-darkening and opacity models, derived from imaging and spectroscopic measurements, are consistent with multiple layering of clouds in the Jovian atmosphere.\r\n\r\nFurther information about the Jovian clouds results from the combination of 5 \u00b5m spectroscopic and imaging data sets. From the shape of the 5 \u00b5m spectrum true maximum brightness temperatures are derived, corrected for the clearest regions in the Jovian atmosphere. Furthermore, from data on spectral line saturation, limits are placed on the 5 \u00b5m cloud reflectivity over the field of view of the spectrometer. With this information, combined with the knowledge of the spatial flux distribution from imaging, constraints are derived for the optical properties of the upper Jovian clouds.\r\n\r\nA three layer cloud model is developed which is consistent with all of the observational data at 5 \u00b5m. The three model cloud layers have cloud top temperatures of T_1 \u2264 190\u00b0K (presumably T_1 \u2243 140\u00b0K), T_2 = 228 \u00b1 2\u00b0K and T_3 = 292 \u00b1 8\u00b0K. The highest layer, found only over the white zones and red spots, has optical depth near unity and transmits radiation from deeper levels. This upper level has a mean\r\n5 \u00b5m cloud reflectivity less than 0.4, while the whole central 25% of the disk has a mean reflectivity less than 0.1. The middle cloud deck is present under the upper level clouds and over the brown colored Jovian belts. This level is optically thick everywhere except in regions where blue-gray areas are visible. Here the middle level thins \r\nto a mean optical depth of about 2 and allows radiation from the deepest and hottest level to be detected.\r\n", "doi": "10.7907/q0w2-hn20", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" }, { "id": "thesis:5708", "collection": "thesis", "collection_id": "5708", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04082010-105350789", "primary_object_url": { "basename": "Hansen_ol_1972.pdf", "content": "final", "filesize": 2725728, "license": "other", "mime_type": "application/pdf", "url": "/5708/1/Hansen_ol_1972.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Thermal Radiation from the Galilean Satellites Measured at 10 and 20 Microns", "author": [ { "family_name": "Hansen", "given_name": "Olav Louis", "clpid": "Hansen-Olav-Louis" } ], "thesis_advisor": [ { "family_name": "Westphal", "given_name": "James A.", "clpid": "Westphal-J-A" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The four Galilean Satellites have been observed in two broad bandpasses, centered near 10\u03bc and 20\u03bc respectively, during Jupiter's 1971-apparition.\r\n\r\nTwo types of measurements were obtained. The first consisted of monitoring the infrared flux as a function of each satellite's orbital position, the other of flux measurements during satellite eclipses. The latter type was \r\nobtained only in the 10\u03bc bandpass, and only for lo (J1), Europa (J2), and Ganymede (J3), because Callisto (J4) was not eclipsed in 1971.\r\n\r\nThe flux measurements obtained as a function of orbital position were averaged for each satellite and bandpass, and from the mean values the following quantities were derived: (1) the maximum (~subsolar) surface temperature, T_(max), (2) the ratio between the effective 20\u03bc emissivity, \r\n\u03b5_(20), and the effective 10\u03bc, emissivity, \u03b5_(10), (3) the bolometric Bond albedo, A_(bol), and (4) the effective phase integral, q. The results, listed in Table (i), indicate very low \"\u03b5_(20)/\u03b5_(10) \" ratios and high q-values.\r\n\r\n\r\nThe 10\u03bc flux measurements obtained during eclipses of J1, J2, and J3 have been compared to thermal models, and the following conclusions were drawn. (1) No homogeneous model [single parameter, y = (kpc)^(-1/2) can account for the observed temperature variations during eclipses. (2) A two- \r\nlayer model with a thin, thermally insulating layer covering a highly conductive subsurface is adequate to explain all the observations. (3) The atmospheric surface pressure on J1, J2, and J3 is less than 1 mbar. (4) The \r\nresults, listed in Table (ii), show that the surface covering of J1 is distinctly different from that of J2 or J3.\r\n", "doi": "10.7907/wn5g-m205", "publication_date": "1972", "thesis_type": "phd", "thesis_year": "1972" } ]