Understanding the evolution of planetary climates and corresponding changes to planetary surfaces involves the study of terrains of various ages and morphologies. Here, I study Endeavour and Jezero, two craters within the martian Noachian Highlands. I use multiple approaches \u2014 including sedimentology, stratigraphy, geomorphology, numerical modeling, and the quantitative study of geologic structures in 3D \u2014 and a combination of orbital images from satellites and on-the-ground or in-situ images from rover-based instruments to conduct detailed and ground-truthed studies at both craters. At each site, I characterize the role of water in shaping the surface and thus constrain the climate of ancient Mars. Also presented in this work is a methodological approach to optimize the usage of rover and orbital images for three-dimensional orientation of geologic structures.
\r\n\r\nIn Chapter 2, I find that rockfall is a potential source of erosion on Endeavour\u2019s crater rim. Repeated events of large clasts bouncing downslope and eroding bedrock could have generated incised landforms in the absence of flowing liquid water. Boulder deposits atop other crater-infilling units indicate the process of rockfall continued during or after the Noachian-Hesperian boundary (~2.5-2.7 Ga), potentially continuing to shape the crater rim morphology after regional surface desiccation. In contrast, the Jezero crater strata at Kodiak butte discussed in Chapter 3 are interpreted as either preserved fluvial bars in a braided river or mouth bars in a shallow lake, indicating water was abundant in the crater. Gravel- sized grains were transported by energetic flows, with minimal quiescent settling of fine-grained sediment. Deposits of such settings may have a lower biosignature preservation potential than those of Gilbert deltas, the previous depositional hypothesis. In Chapter 4, I performed traces of beds of the Jezero delta-fan structure in HiRISE and then used apparent dips of a given feature seen from multiple perspectives in rover images to estimate true surface orientations. I confirmed that the orientations of scarps, beds, or other quasi-planar surfaces measured from the highest-available resolution orbital datasets are accurate. However, it is challenging to distinguish hierarchical stratigraphic elements from each other and from erosional surfaces using orbital data, and therefore rover data adds key context for depositional interpretations that inform paleoenviroment. In particular, bedform internal structures could only be determined from rover datasets. In all, through a synthesis of methodological approaches and datasets, I find that the two studied craters potentially record disparate predominant morphology-shaping forces \u2014 dry rockfall in Endeavour, and fluvio-lacustrine activity at Jezero. These sites provide spatial and temporal snapshots of past surface conditions on Mars that can be used to build a more complete narrative of the planet\u2019s history.
", "doi": "10.7907/dry1-3w54", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17045", "collection": "thesis", "collection_id": "17045", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03052025-175659528", "primary_object_url": { "basename": "ParraSergio_PhdThesis_Final.pdf", "content": "final", "filesize": 9240598, "license": "other", "mime_type": "application/pdf", "url": "/17045/1/ParraSergio_PhdThesis_Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Location, Location, Location: Insights from Spatially-Resolved Observations of Marine Seep Carbonate Ecosystems and Carbonaceous Chondrite Surfaces", "author": [ { "family_name": "Parra", "given_name": "Sergio Alexander", "orcid": "0000-0002-2637-7960", "clpid": "Parra-Sergio-Alexander" } ], "thesis_advisor": [ { "family_name": "Orphan", "given_name": "Victoria J.", "orcid": "0000-0002-5374-6178", "clpid": "Orphan-V-J" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Fischer", "given_name": "Woodward W.", "orcid": "0000-0002-8836-3054", "clpid": "Fischer-W-W" }, { "family_name": "Orphan", "given_name": "Victoria J.", "orcid": "0000-0002-5374-6178", "clpid": "Orphan-V-J" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Meile", "given_name": "Christof", "orcid": "0000-0002-0825-4596", "clpid": "Meile-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Spatially heterogeneous, multi-component systems are prevalent topics of study in geobiology and planetary science. However, previous studies of these systems often represent limited measurements that abstract or separate the sample from its localized context, thereby obscuring or precluding insights into the drivers ultimately shaping these systems. This challenge motivates the work presented in this thesis, where we provide an extensive and spatially-resolved examination of two complex, heterogeneous systems in geobiology and planetary science: marine seep carbonates and carbonaceous chondrite surfaces, respectively. In marine seep systems worldwide, seep carbonates are a mineral byproduct of a microbial metabolism (the anaerobic oxidation of methane, or AOM) and can continue hosting metabolically active microbial communities, including methane-oxidizing microbes. However, much of our understanding of these endolithic microbial communities stems from bulk, centimeter-scale evaluations of microbial identity and/or metabolic activity across a limited number of samples. As such, the range of structural and environmental conditions that ultimately shape the degree and extent of microbial activity in seep carbonates, including AOM, remains relatively under-constrained. To address this gap, Chapters 1-3 investigate carbonate-hosted microbial communities at a methane seep site in Santa Monica. In Chapter 1, we explore carbonate \u2018nodules\u2019 from methane seep sediments at and below the sulfate-methane transition zone (SMTZ), analyzing their mineral composition, internal structures, and hosted microbial communities compared to their host sediment communities and porewater chemistry. We also discuss key implications of the connectivity of seep sediments to nodules over geologic timescales and the preservation of microbial \u2018thumbprints\u2019. Chapter 2 describes rare tripartite associations between two groups of anaerobic methanotrophic archaea (ANME-1 and ANME-2) and a bacterial partner within seep carbonate crusts and other substrates at the seafloor, with implications towards understudied diversity in the syntrophic interactions governing AOM beyond seep carbonates. Chapter 3 examines the impact of seep carbonate internal structure on endolithic communities from various carbonate crusts, revealing similarities and differences between surface and interior communities that may reflect the importance of pore networks in maintaining favorable local environments. In Chapter 4, we pivot to an extensive analysis of spectra from carbonaceous chondrite surfaces. Carbonaceous chondrites (CCs) are a group of meteorites that represent the oldest materials in the solar system, whose mineralogy preserves a record of early alteration processes thought to be shared with certain asteroids. However, most studies connecting specific CCs to specific asteroids have relied on spectroscopic measurements of bulk powder CCs, which are spatially unresolved and destroy textures, thereby hindering tying shared spectral features to particular phases, petrologic contexts, and alteration histories. As such, Chapter 4 presents an analysis of CCs measured using microimaging hyperspectral visible-and-shortwave-infrared (VSWIR) spectroscopy, where we capture chondrite surfaces features at high spatial resolution. We also compare CC spectral features with asteroids using the Expanded Bus-DeMeo taxonomy, which provides a systematic framework to examine and identify shared drivers of spectral diversity within this spectral range, including Fe-bearing minerals from both original and terrestrial alteration processes. Together, these studies emphasize the importance of spatially-resolved sampling across disciplines, specifically in geobiology and planetary science, thereby capturing and highlighting the heterogenous nature of key systems in these fields and bettering our understanding of the factors shaping them.", "doi": "10.7907/c0w0-ns76", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:14607", "collection": "thesis", "collection_id": "14607", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05252022-013922276", "primary_object_url": { "basename": "Scheller_thesisdocument_March2022_final_edited.pdf", "content": "final", "filesize": 70105539, "license": "other", "mime_type": "application/pdf", "url": "/14607/4/Scheller_thesisdocument_March2022_final_edited.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "A Multi-Disciplinary Approach: How Aqueous Minerals Hold the Key to Understanding the Climate and Habitability of Terrestrial Planets", "author": [ { "family_name": "Scheller", "given_name": "Eva Linghan", "orcid": "0000-0002-9981-5802", "clpid": "Scheller-Eva-Linghan" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Understanding the interplay between geological processes and the climate within the ancient pasts of terrestrial planets holds the key to deciphering what makes terrestrial planets habitable. The climates of both Mars and Earth were drastically different in their ancient pasts. Liquid water once flowed on Mars ~3-4 Ga, creating fluvial valleys and aqueous minerals, until Mars dried out to the desert planet we know today. During the Pleistocene (~ 2.6 Ma \u2013 11.7 ka) and Neoproterozoic (640-710 Ma), Earth experienced widespread glaciations and even a global glaciated state, respectively. Aqueous minerals, such as clays and carbonates, record the history of their aqueous environments and can be used to track these dramatic changes in climate and environment. In Chapter 2, I use hyperspectral infrared imagery and high resolution images retrieved by the Mars Reconnaissance Orbiter to characterize the lithology of some of the oldest Noachian ~3.8-4.1 Ga crust exposed on Mars. I document eight geological units and features that will be studied with the Perseverance rover and record the presence of pyroxene-bearing igneous crustal materials, aqueous environments that led to widespread clay formation, and basin-forming impact processes that brecciated the crust. Associated younger Noachian-aged magnesium carbonate-bearing geological units will also be studied and sampled with the Perseverance rover. In Chapter 3, I review magnesium carbonate formation on Earth and Mars and find that textures of nodules, crusts, veins, sparry crystals, and thrombolites/stromatolites, their associated host lithologies and related secondary mineralogy can be used to distinguish between formation within weathering, lacustrine, hydrothermal, diagenetic, or microbially influenced aqueous environments, respectively, with rover analyses. Laboratory analysis of stable and radiogenic isotopes of returned samples will allow us to analyze the surface temperature and atmospheric isotopic composition of ancient Mars. In Chapter 4, I characterize the paragenesis of hydrated carbonates. In frigid environments, carbonates form in hydrated species known as monohydrocalcite (MHC) and ikaite that transform to calcite upon heating. Through petrographic analysis of Pleistocene ikaite pseudomorphs and a review of more ancient examples, I define a new carbonate microtexture, guttulatic calcite, which is diagnostic for carbonate dehydration and can be used to document frigid temperature conditions. In Chapter 5, I characterize the stable carbon, oxygen (\u03b4\u00b9\u2078OCARB), and clumped (\u0394\u2084\u2087) isotope systematics of hydrated carbonates. Through heating experiments of modern MHC, I measure and model change in \u03b4\u00b9\u2078OCARB and \u0394\u2084\u2087 signatures facilitated by equilibrium exchange as MHC is dehydrated. Using the determined correction for dehydration overprint allows reconstruction of precursor ikaite formation temperatures and isotopic signatures. The textural and isotopic proxies can now be used for reconstructing temperatures and isotopic signatures within Pleistocene and Neoproterozoic sedimentary deposits. In Chapter 6, I use the Perseverance rover\u2019s SHERLOC instrument\u2019s deep-UV Raman and fluorescence spectroscopy to discover evidence for two potentially habitable ancient aqueous environments that contain aromatic organic compounds. Spectral and textural observations of the olivinecarbonate assemblage within Jezero crater, Mars reveal carbonation of ultramafic protolith. A separate, later brine formed sulfate-perchlorate mixtures in void spaces. Fluorescence signatures consistent with multiple types of aromatic organic compounds occur throughout these samples, preserved in minerals related to both aqueous processes. These organic-mineral associations indicate that aqueous alteration processes led to the preservation and possibly formation of organic compounds on Mars. In Chapter 7, I model the global water budget and hydrogen isotopic composition (D/H) of Mars, using measured constraints from geomorphology, atmospheric escape rates, volcanic degassing processes, crust volatile content, and D/H. In my simulations, I find that chemical weathering sequestered a 0.1-1 km global equivalent layer of water, decreasing the volume of water participating in the hydrological cycle by 40 to 95% over the Noachian (~3.7-4 Ga) period, reaching present-day values by ~3 Ga. Between 30 and 99% of Martian water was sequestered through crustal hydration, demonstrating that irreversible chemical weathering can increase the aridity of terrestrial planets. In summary, this PhD thesis demonstrates that the formation of aqueous minerals is a major control on terrestrial planet climates and that aqueous minerals can be used to track the conditions of their formation environments.
", "doi": "10.7907/8rj3-6k52", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14167", "collection": "thesis", "collection_id": "14167", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05202021-183729767", "primary_object_url": { "basename": "RobackThesis-final.pdf", "content": "final", "filesize": 6346301, "license": "other", "mime_type": "application/pdf", "url": "/14167/2/RobackThesis-final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Investigating Sand Transport and Landslides, and Implications for Past and Present Environments on Mars and Earth", "author": [ { "family_name": "Roback", "given_name": "Kevin Patrick", "orcid": "0000-0001-5209-2873", "clpid": "Roback-Kevin-Patrick" } ], "thesis_advisor": [ { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "orcid": "0000-0002-2035-9198", "clpid": "Ingersoll-A-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "orcid": "0000-0002-3060-8442", "clpid": "Avouac-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Wind-driven movement of sand and landslide activity are among the most important processes driving modern-day change on planetary surfaces. This thesis uses novel techniques and datasets to investigate the forces driving these processes on the surface of Mars, and also considers possible applications of the techniques described to Earth. Chapter 1 introduces past work done to understand these processes, and outstanding questions our work aims to answer. Chapter 2 presents and tests a new technique which aims to improve predictions of sand transport driven by wind on planetary surfaces by correcting coarse-resolution GCM predictions for the short-timescale fluctuations they miss. Chapter 3 presents new multiyear measurements of ripple migration at two dune fields on the surface of Mars, and applies these measurements, in conjunction with the new techniques described in Chapter 2, to investigate the dynamics of the Martian atmosphere, and test the accuracy of predictions made by Martian climate models. In Chapter 4, we study a large-scale natural sand trap in the Meroe Patera dune field on Mars, and estimate its trapped volume of sand in comparison to the volume of \"missing\" sand in a dune-free shadow zone downwind of the crater. The volume of trapped sand is far less than the missing volume, suggesting past escape of sand from the crater, despite a lack of obvious evidence for such escape in the present day. In Chapter 5, we change focus from sand transport to introduce an analysis of controls on the global distribution of Martian landslides. Chapter 6 discusses the limitations of applying the techniques of satellite image and climate model analysis described in Chapters 2-4 to terrestrial settings, as well as the possible utility of Chapter 5\u2019s method on other planets.
", "doi": "10.7907/gykg-wz60", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13642", "collection": "thesis", "collection_id": "13642", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02192020-182835054", "type": "thesis", "title": "Investigating the Evolution of Surface Water on Mars through Spectroscopy of Secondary Minerals", "author": [ { "family_name": "Leask", "given_name": "Ellen Kathleen", "orcid": "0000-0002-3220-4003", "clpid": "Leask-Ellen-Kathleen" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Fischer", "given_name": "Woodward W.", "clpid": "Fischer-W-W" }, { "family_name": "Frankenberg", "given_name": "Christian", "clpid": "Frankenberg-C" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Despite its current arid climate, Mars\u2019 surface preserves a wide variety of morphologies and minerals that point to a water-rich past. However, the mechanisms and timing of this environmental change are not yet well understood. In this dissertation, we explore a variety of water-related minerals through visible-shortwave infrared (VSWIR) reflectance spectroscopy to better understand the environmental conditions at the time of their formation, and trace the evolution of surface water on Mars over time. We also demonstrate the capabilities of VSWIR spectroscopy at laboratory and field scales in a Mars analogue environment (Samail Ophiolite, Oman)\u2014an emerging technique for use on future landed missions that enables us to differentiate between spectrally-similar minerals and spot rare minerals that help to constrain environmental conditions and better understand the geologic context of samples. On Mars, we use orbital datasets (predominantly CRISM, the Compact Reconnaissance Imaging Spectrometer for Mars) to investigate secondary minerals in the southern highlands of Mars, focusing on perchlorate, chloride, and sulphate minerals. We identify a previously unknown artifact in the CRISM dataset, which mimics perchlorate absorptions; previous orbital perchlorate detections (including those associated with recurring slope lineae) are not robust when data are reprocessed, suggesting that there may not be orbitally-detectable reservoirs of perchlorate on Mars, which would enable liquid brines to exist at the surface today. A detailed investigation of chloride deposits across the southern highlands of Mars points to an episodic surface-runoff water source rather than upwelling groundwater, a process which continued to create chloride deposits into the Amazonian era. Where chloride and sulphate deposits are in close proximity (Terra Sirenum, Mars), they do not appear to be genetically related as they often are on Earth; instead, they point to chemically distinct groundwater vs. surface water reservoirs in Terra Sirenum through the Hesperian and into the Amazonian. Together, these studies indicate that briny and/or acidic volumes of water at the surface capable of creating mineral deposits continued to exist \u2014 at least episodically \u2014 on Mars into the Amazonian, rather than ceasing much earlier in Mars\u2019 history.
", "doi": "10.7907/TWR4-N128", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13810", "collection": "thesis", "collection_id": "13810", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06092020-122543624", "primary_object_url": { "basename": "Stein_Thesis_Final.pdf", "content": "final", "filesize": 106613613, "license": "other", "mime_type": "application/pdf", "url": "/13810/1/Stein_Thesis_Final.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Investigation of Past Habitable Environments through Remote Sensing of Planetary Surfaces", "author": [ { "family_name": "Stein", "given_name": "Nathaniel Thomas", "orcid": "0000-0003-3385-9957", "clpid": "Stein-Nathaniel-Thomas" } ], "thesis_advisor": [ { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" }, { "family_name": "Fischer", "given_name": "Woodward W.", "clpid": "Fischer-W-W" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Planetary surfaces record a history of potentially habitable environments throughout the solar system. This dissertation focuses on the characterization of three planetary surfaces to inform their evolution and past habitability: Earth (Chapter 2), Mars (Chapters 3-4), and Ceres (Chapters 5-6). In chapter 1, we introduce major questions driving the work presented in this thesis. In Chapter 2, we use a combination of UAV-based images and in-situ observations to characterize the processes that control the texture and distribution of modern microbial mats in the Turks and Caicos. We find that the surface texture and distribution of the mats is controlled primarily by subtle differences in elevation that drive significant changes in subaerial exposure time. Sedimentation and mechanical weathering from storm events also play a key role in controlling the distribution of mats. In Chapter 3, we apply a PCA-based regression method to stereo Curiosity Mastcam images to measure the structural orientation of the Murray formation. We constrain the dip to be effectively horizontal, which indicates that the Murray formation predates the creation of Aeolis Mons and is consistent with flat strata being deposited on an equipotential surface in a lacustrine setting. In Chapter 4, we summarize the investigation of networks of reticulate ridges on the surface of several rock slabs in the Murray formation using data from the Curiosity rover. We find that the features are preserved mudcracks that were likely deposited during a lowstand in a lake ~3.2-3.6 Ga. The mudcracks are one of few definitive textural markers of drying in the Murray formation and suggest a history of oscillating lake levels that led to intermittent exposure. In Chapter 5, we catalog bright spots on Ceres and propose mechanisms for their formation. We identify hundreds of Na-carbonate-bearing regions on Ceres. We show with a Monte Carlo impact model that these deposits must have been exposed within the last few hundred Ma. In Chapter 6, we investigate the source of shallow subsurface Na-carbonate deposits. We show that the deposits must have been emplaced in the last ~1 Ga and that the solid-state mobilization of water ice and hydrated Na-carbonates could simultaneously explain the formation of domes and large crater rim Na-carbonate exposures. Chapter 7 synthesizes the major results of this thesis and avenues for future exploration.", "doi": "10.7907/cq9c-sg21", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:11711", "collection": "thesis", "collection_id": "11711", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072019-115333958", "primary_object_url": { "basename": "NThomas_Thesis_revised_submitted_compressed.pdf", "content": "final", "filesize": 9940420, "license": "other", "mime_type": "application/pdf", "url": "/11711/1/NThomas_Thesis_revised_submitted_compressed.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Remotely Sensing Aqueous Alteration on Mars: Innovative Statistical and Analytical Methods for Large Spectral Datasets", "author": [ { "family_name": "Thomas", "given_name": "Nancy Helen", "orcid": "0000-0003-1989-4860", "clpid": "Thomas-Nancy-Helen" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Knutson", "given_name": "Heather A.", "clpid": "Knutson-H-A" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" }, { "family_name": "Fischer", "given_name": "Woodward W.", "clpid": "Fischer-W-W" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Liquid water once flowed on Mars and altered the crust. Aqueous minerals and salts record a rich history of aqueous processes and environmental changes. In this dissertation, I developed and applied innovative analytical and statistical methods to large spectral datasets to better characterize aqueous alteration on Mars. The Mars Science Laboratory (MSL) Curiosity rover is investigating the sedimentary sequence at Gale crater recording a potentially global transition from clay-enriched to sulfate-enriched rocks. Volatile elements like H and Cl are important for investigating aqueous processes but are difficult to quantify in the large ChemCam laser-induced breakdown spectroscopy (LIBS) dataset. In the first part of this dissertation, I measured aqueously altered samples with LIBS in the laboratory under Mars-relevant conditions to develop analytical methods for application to ChemCam. The Murray formation, the lowest exposed strata of the sedimentary sequence, contains 2.6 \u00b1 2.1 wt. % H2O. Carriers of H enrichment including clays, opal, Mg-sulfates, Ca-sulfates, hydrous Mn-oxides, akageneite, and jarosite are identified. Variability in the H content of the Murray formation records multiple aqueous alteration events as well as potential increases in salinity in the Gale crater lake. In the fourth chapter, I measured chlorine in Gale crater using multiple MSL instruments. Cl-enrichments correlated with increased Na2O are detected in the bedrock, in nodular textures, and at vein margins, indicating halite. The scattered, isolated occurrences of chlorides are consistent with late groundwater reworking and remobilization. Halite is concentrated in particular members of the Murray formation; the chlorides may have been emplaced as primary deposits in these members, consistent with varying salinity in the past lakewaters. In the second part of this dissertation, I adapted and applied semi-automated statistical methods called factor analysis and target transformation to the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) dataset to systematically search for hematite in stratified, candidate sedimentary outcrops. Few outcrops containing hematite are found and no obvious analogs to terrestrial iron formations are identified. Future studies will search for hematite in other geologic settings as well as other Fe-bearing phases such as Fe-phyllosilicates and Fe-sulfates to better characterize aqueous processes on Mars.", "doi": "10.7907/8JFC-BY64", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:10990", "collection": "thesis", "collection_id": "10990", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312018-155112365", "primary_object_url": { "basename": "Thesis_v4.pdf", "content": "final", "filesize": 11364608, "license": "other", "mime_type": "application/pdf", "url": "/10990/1/Thesis_v4.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Measuring and Modeling the Interplay between Planetary Orbits, Interiors, Surfaces, and Atmospheres", "author": [ { "family_name": "Buhler", "given_name": "Peter Benjamin", "orcid": "0000-0002-5247-7148", "clpid": "Buhler-Peter-Benjamin" } ], "thesis_advisor": [ { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Avouac", "given_name": "Jean-Philippe", "clpid": "Avouac-J-P" }, { "family_name": "Tsai", "given_name": "Victor C.", "clpid": "Tsai-V-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Typically, we only have access to observations that directly probe the instantaneous state of a planet. However, these instantaneous properties are often set by the long-term interplay between several aspects of the planet. I thus use quantitative models of the interactions between the orbital, interior, surface, and atmospheric evolution in the case of three planetary bodies (Mars, Pluto, and the extrasolar planet HAT-P-13b) to gain insight into the underlying physical processes that govern the evolution of planets.
\r\n\r\nIn chapter 2, the interplay between the interior structure and orbital evolution of the gas giant exoplanet HAT-P-13b allows measurements of its orbit to reveal its interior structure. I use telescopic observations of HAT-P-13b to measure its orbit and thus determine its core mass.
\r\n\r\nIn chapter 3, cell-shaped landforms on Sputnik Planitia, the surface of a vast deposit of nitrogen ice covering 5% of Pluto\u2019s surface, are the surface expression of convection within the nitrogen ice that is driven by heat flow from Pluto\u2019s interior. The cells have sublimation pits on them, with smaller pits near their centers and larger pits near their edges. Using a simple model, I calculate the sublimation rate of these pits, which allows the determination of a size-age relationship. I then use the spatial size distribution of pits on cells to calculate their convection rate, which constrains the plutonian heat flow and thus the interior properties of Pluto.
\r\n\r\nIn chapter 4, the interplay of condensation and sublimation between the surface and atmosphere of Mars create a baffling array of uniquely martian morphologies carved into the martian residual south polar CO2 cap (RSPC). Using a multi-year baseline of high-resolution observations to track the evolution of these morphologies, I build a self-consistent conceptual framework capable of explaining the basic mechanisms that give rise to the diversity of landforms that make up the RSPC.
\r\n\r\nIn chapter 5, the secular evolution of Mars' orbit drives the evolution of the equilibrium relationship between the martian atmospheric pressure and the large CO2 ice deposit on the martian south polar cap. I construct the first self-consistent conceptual framework capable of predicting the existence and form of the martian residual south polar cap and the buried CO2 deposit. I then use this framework to compute the secular pressure history of Mars.
\r\n\r\nTogether, the results of these investigations provide new perspective into the fundamental processes driving the formation and evolution of planetary bodies.
\r\n", "doi": "10.7907/MEXZ-2586", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10953", "collection": "thesis", "collection_id": "10953", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282018-115947263", "primary_object_url": { "basename": "Daven-Quinn-thesis-2018.pdf", "content": "final", "filesize": 155896431, "license": "other", "mime_type": "application/pdf", "url": "/10953/9/Daven-Quinn-thesis-2018.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Regional Structural Geology of Earth and Mars", "author": [ { "family_name": "Quinn", "given_name": "Daven Patel", "orcid": "0000-0003-1895-3742", "clpid": "Quinn-Daven-Patel" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "thesis_committee": [ { "family_name": "Stock", "given_name": "Joann M.", "orcid": "0000-0003-4816-7865", "clpid": "Stock-J-M" }, { "family_name": "Eiler", "given_name": "John M.", "orcid": "0000-0001-5768-7593", "clpid": "Eiler-J-M" }, { "family_name": "Asimow", "given_name": "Paul David", "orcid": "0000-0001-6025-8925", "clpid": "Asimow-P-D" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "This thesis explores the geologic context around several key environmental transitions on Earth and Mars which are expressed at continental margins. Regional mapping techniques are applied to build links between methodologies used to explore rock samples and units \u2014 stratigraphy, structural geology, remote sensing, geochemistry, petrology, and geodynamic modeling. Four research projects are presented: Chapter 2 explores the tectonic context of xenoliths beneath the western margin of North America and illuminates the structural history of the lithospheric underpinnings of the California coast. In Chapter 3, we undertake a structural study of the southern Naukluft Mountains, Namibia, and re-interpret its tectonic context and age. Chapter 4 builds a new method for applying statistical errors to remotely measured planar orientations, and Chapter 5 applies this method to mapping the 3D structure of a globally significant stratigraphy on Mars. We find a long history of interaction with water at the margin of Isidis Basin. Together, these projects demonstrate the application of structural techniques to continental margins on Earth and Mars, and the creation of new techniques to support geological analysis from remotely-sensed data, where structural measurements may be poorly resolved.", "doi": "10.7907/9enj-wn23", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10932", "collection": "thesis", "collection_id": "10932", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05242018-144308725", "primary_object_url": { "basename": "Buz_Thesis_Macro_Micro_Mars_final.pdf", "content": "final", "filesize": 11918023, "license": "other", "mime_type": "application/pdf", "url": "/10932/27/Buz_Thesis_Macro_Micro_Mars_final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Macro Mars to Micro Mars: Mapping Minerals and Magnetization", "author": [ { "family_name": "Buz", "given_name": "Jennifer", "orcid": "0000-0002-0491-2686", "clpid": "Buz-Jennifer" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" } ], "thesis_committee": [ { "family_name": "Lamb", "given_name": "Michael P.", "orcid": "0000-0002-5701-0504", "clpid": "Lamb-M-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "orcid": "0000-0002-2745-3240", "clpid": "Ehlmann-B-L" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Fischer", "given_name": "Woodward W.", "orcid": "0000-0002-8836-3054", "clpid": "Fischer-W-W" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Combination of remote sensing data with in-situ measurements provides a fuller understanding of Mars phenomena. This dissertation focuses on integrating macroscopic and microscopic scales of measurement with regard to spectroscopy and magnetization. In the first chapter high resolution orbital spectroscopy (~18 m/px) and imagery (~30 cm/px) are used to identify potential sources for some of the sedimentary rocks investigated by the Curiosity rover and expand the accessible stratigraphy. While we find mineralogies in common outside and inside the crater as well as transport mechanisms, we conclude that additional sedimentary sources and/or modification after transport are required to explain chemical differences and that strata point to multiple episodes of a lake in Gale crater. In the third chapter we conducted a laboratory photometric study on candidate calibration target materials for the Mars-2020 rover. We characterized these target materials for proper calibration and monitoring of the Mastcam-Z instrument to enable mineral identification through reflectance spectroscopy. The fourth and fifth chapters focus on the microscopic magnetizations found within Martian meteorite ALH84001. Chapter four reports on paleomagnetic experiments conducted on isolated carbonate crystals which contain magnetite previously reported to be biogenic. We compare paleomagnetic test results which distinguish between biogenic and abiogenic origin hypotheses and find that the magnetization within the carbonates is most consistent with a shock processes. In chapter five we analyzed the distribution of dipoles within slices of ALH84001 and determined that they lie in a girdle distribution which could be interpreted as resulting from a true polar wander event on Mars. Looking at kilometer scale observations outside of Gale enlightened observations made along the rover transverse path. A high resolution laboratory analysis of calibration materials will enable future multispectral mineralogical explorations. Microscopic analyses of magnetization inform ancient surface processes on Mars and hint at large-scale global change. In each of these chapters our results were only made possible or greatly enhanced by the combination of data sources and scales.
", "doi": "10.7907/Z6EH-M526", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10136", "collection": "thesis", "collection_id": "10136", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04132017-163326100", "type": "thesis", "title": "Insights into the Geologic History of Mars\u2019 Northern Lowlands from Near-Infrared Spectroscopy \r ", "author": [ { "family_name": "Pan", "given_name": "Lu", "orcid": "0000-0002-8151-2125", "clpid": "Pan-Lu" } ], "thesis_advisor": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Hydrated minerals, identified on Mars using near-infrared spectroscopy data, reveal new insights into the aqueous processes and evolution of climate in the history of Mars. Through investigations of the mineralogical record using near-infrared spectroscopy, this dissertation focuses on the geologic history and aqueous processes in the northern lowlands of Mars in order to assess the existence of a long-lived global ocean, the extent and volume of Noachian-Hesperian volcanic flows filling the northern lowlands, the nature of aqueous activity in the most recent Amazonian age, and the spectral variability of carbonates. The first chapter reports widespread and diverse mafic and hydrated mineralogy of units associated with impact craters across the northern lowlands. In the lowlands-wide survey, no pervasive carbonate or evaporative salts are found in support of a northern ocean, but we identify widespread phyllosilicates inferred to be Noachian basement materials excavated beneath 1-2 km of mafic lava flows. In the second and third chapters, combined analysis of imagery and spectral data is used to investigate local geologic processes related to liquid water in the knobby terrains of Acidalia and in the vicinity of Lyot crater. Phyllosilicates and hydrated silica are detected in the knobby terrains of Acidalia indicative of a declining prevalence of aqueous alteration through time. We also find diverse mineralogy in the vicinity of Lyot, probably formed in a hydrothermal system and later excavated by the Lyot impact. In contrast, we did not identify mineralization related to local channels that are syn- or post-impact. The fourth study analyzes the spectral properties of unshocked and impact-shocked carbonate rocks on Earth and found similar spectral characteristics between Mars carbonate detections and terrestrial carbonates in impact environments. Using near-infrared spectroscopy, we have identified and characterized the mineralogic record of Mars, and found past environments within the northern lowlands of Mars with varying style and intensity of aqueous alteration through time, with implications for the evolution of Mars climate.
", "doi": "10.7907/Z94747WX", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10173", "collection": "thesis", "collection_id": "10173", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05152017-105730412", "type": "thesis", "title": "Sedimentary Processes on Earth and Mars: Canyon Erosion, Sand-Ripple Formation, and Mineral Composition", "author": [ { "family_name": "Lap\u00f4tre", "given_name": "Mathieu Gaetan Andre", "orcid": "0000-0001-9941-1552", "clpid": "Lap\u00f4tre-Mathieu-Gaetan-Andre" } ], "thesis_advisor": [ { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" }, { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" } ], "thesis_committee": [ { "family_name": "Ehlmann", "given_name": "Bethany L.", "clpid": "Ehlmann-B-L" }, { "family_name": "Lamb", "given_name": "Michael P.", "clpid": "Lamb-M-P" }, { "family_name": "Grotzinger", "given_name": "John P.", "clpid": "Grotzinger-J-P" }, { "family_name": "Farley", "given_name": "Kenneth A.", "clpid": "Farley-K-A" }, { "family_name": "Golombek", "given_name": "Matthew P.", "clpid": "Golombek-M-P" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_gps" } ], "abstract": "Over the past few decades, orbiters, landers, and rovers have significantly expanded our understanding of Mars\u2019 hydrology and climate; however, significant knowledge gaps stand in the way of our quest for martian life. In particular, the global drying of the planet remains one of the grandest unsolved mysteries in planetary science. To help unravel this puzzle, we develop new quantitative theories for sedimentary processes with implications for both Earth and Mars. This thesis revolves around three main sedimentary processes \u2013 erosion, deposition, and sediment transport. First, we focus on the erosion of bedrock canyons by water on Earth and Mars. After showing that groundwater seepage erosion is only efficient at carving canyons in restricted conditions, we develop a new hydraulic theory for flow focusing upstream of horseshoe-shaped waterfalls and combine it with waterfall-erosion mechanics to constrain the discharge, duration, and volume of canyon-carving floods on Earth and Mars. We show that martian Hesperian floods were large but short-lived. Second, we investigate fluid and sediment controls on the equilibrium size of bedforms. We develop a comprehensive scaling relation to predict the size of ripples forming in various sedimentary environments, including martian brines and methane flows on Titan, and show that the scaling relation predicts the size of large wind ripples forming under a thin martian atmosphere. This new theory, combined with observations of large-ripple cross-strata in wind-blown sandstones of the Burns formation at Victoria crater, suggests that Mars had a thin atmosphere around the Noachian-Hesperian boundary. Finally, we use orbiter-based inferences of the mineralogy of sands of the Bagnold dunes of Gale crater to disentangle the magnitude of wind sorting and local sediment sources. We develop a new probabilistic framework to invert for surface mineralogy, groundtruth our predictions with compositional datasets provided by the Curiosity rover, and discuss the implications of our findings for mineral sorting by martian winds and paleoenvironmental interpretations of martian wind-blown sandstones. Collectively, these results provide new mechanistic and quantitative constraints on the past hydrology and climate of Mars that are key to assess Mars\u2019 astrobiological potential through space and time.", "doi": "10.7907/Z9RF5S2T", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" } ]