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Description
The occurrence of exogenic, meteoritic materials on the surface of any world presents opportunities to explore a variety of significant problems in the planetary sciences. In the case of Mars, meteorites found on its surface may help to 1) constrain atmospheric conditions during their time of arrival; 2) provide insights into possible variabilities in meteoroid type sampling between Mars and Earth space environments; 3) aid in our understanding of soil, dust, and sedimentary rock chemistry; 4) assist with the calibration of crater-age dating techniques; and 5) provide witness samples for chemical and mechanical weathering processes. The presence of reduced metallic iron in approximately 88 percent of meteorite falls renders the majority of meteorites particularly sensitive to oxidation by H2O interaction. This makes them excellent markers for H2O occurrence. Several large meteorites have been discovered at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers (MERs). Significant morphologic characteristics interpretable as weathering features in the Meridiani suite of iron meteorites include a 1) large pit lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; 2) differentially eroded kamacite and taenite lamellae on three of the meteorites, providing relative timing through cross-cutting relationships with deposition of 3) an iron oxide-rich dark coating; and 4) regmaglypted surfaces testifying to regions of minimal surface modification; with other regions in the same meteorites exhibiting 5) large-scale, cavernous weathering. Iron meteorites found by Mini-TES at both Meridiani Planum and Gusev Crater have prompted laboratory experiments designed to explore elements of reflectivity, dust cover, and potential oxide coatings on their surfaces in the thermal infrared using analog samples. Results show that dust thickness on an iron substrate need be only one tenth as great as that on a silicate rock to obscure its infrared signal. In addition, a database of thermal emission spectra for 46 meteorites was prepared to aid in the on-going detection and interpretation of these valuable rocks on Mars using Mini-TES instruments on both MER spacecraft. Applications to the asteroidal sciences are also relevant and intended for this database.
ContributorsAshley, James Warren (Author) / Christensen, Philip R. (Thesis advisor) / Sharp, Thomas G (Committee member) / Shock, Everett L (Committee member) / Hervig, Richard L (Committee member) / Zolotov, Mikhail Y (Committee member) / Arizona State University (Publisher)
Created2011
Description
Water is a critical resource for future human missions, and is necessary for understanding the evolution of the Solar System. The Moon and Mars have water in various forms and are therefore high-priority targets in the search for accessible extraterrestrial water. Complementary remote sensing analyses coupled with laboratory and field studies are necessary to provide a scientific context for future lunar and Mars exploration. In this thesis, I use multiple techniques to investigate the presence of water-ice at the lunar poles and the properties of martian chloride minerals, whose evolution is intricately linked with liquid water.
Permanently shadowed regions (PSRs) at the lunar poles may contain substantial water ice, but radar signatures at PSRs could indicate water ice or large block populations. Mini-RF radar and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) products were used to assess block abundances where radar signatures indicated potential ice deposits. While the majority of PSRs in this study indicated large block populations and a low likelihood of water ice, one crater – Rozhdestvenskiy N – showed indirect indications of water ice in its interior.
Chloride deposits indicate regions where the last substantial liquid water existed on Mars. Major ion abundances and expected precipitation sequences of terrestrial chloride brines could provide context for assessing the provenance of martian chloride deposits. Chloride minerals are most readily distinguished in the far-infrared (45+ μm), where their fundamental absorption features are strongest. Multiple chloride compositions and textures were characterized in far-infrared emission for the first time. Systematic variations in the spectra were observed; these variations will allow chloride mineralogy to be determined and large variations in texture to be constrained.
In the present day, recurring slope lineae (RSL) may indicate water flow, but fresh water is not stable on Mars. However, dissolved chloride could allow liquid water to flow transiently. Using Thermal Emission Imaging System (THEMIS) data, I determined that RSL are most likely not fed by chloride-rich brines on Mars. Substantial amounts of salt would be consumed to produce a surface water flow; therefore, these features are therefore thought to instead be surface darkening due to capillary wicking.
Permanently shadowed regions (PSRs) at the lunar poles may contain substantial water ice, but radar signatures at PSRs could indicate water ice or large block populations. Mini-RF radar and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) products were used to assess block abundances where radar signatures indicated potential ice deposits. While the majority of PSRs in this study indicated large block populations and a low likelihood of water ice, one crater – Rozhdestvenskiy N – showed indirect indications of water ice in its interior.
Chloride deposits indicate regions where the last substantial liquid water existed on Mars. Major ion abundances and expected precipitation sequences of terrestrial chloride brines could provide context for assessing the provenance of martian chloride deposits. Chloride minerals are most readily distinguished in the far-infrared (45+ μm), where their fundamental absorption features are strongest. Multiple chloride compositions and textures were characterized in far-infrared emission for the first time. Systematic variations in the spectra were observed; these variations will allow chloride mineralogy to be determined and large variations in texture to be constrained.
In the present day, recurring slope lineae (RSL) may indicate water flow, but fresh water is not stable on Mars. However, dissolved chloride could allow liquid water to flow transiently. Using Thermal Emission Imaging System (THEMIS) data, I determined that RSL are most likely not fed by chloride-rich brines on Mars. Substantial amounts of salt would be consumed to produce a surface water flow; therefore, these features are therefore thought to instead be surface darkening due to capillary wicking.
ContributorsMitchell, Julie (Author) / Christensen, Philip R. (Thesis advisor) / Bell Iii, James F (Committee member) / Desch, Steven J (Committee member) / Hartnett, Hilairy E (Committee member) / Robinson, Mark S (Committee member) / Arizona State University (Publisher)
Created2017
Description
The seasonal deposition of CO2 on the polar caps is one of the most dynamic processes on Mars and is a dominant driver of the global climate. Remote sensing temperature and albedo data were used to estimate the subliming mass of CO2 ice on south polar gullies near Sisyphi Cavi. Results showed that column mass abundances range from 400 - 1000 kg.m2 in an area less than 60 km2 in late winter. Complete sublimation of the seasonal caps may occur later than estimated by large-scale studies and is geographically dependent. Seasonal ice depth estimates suggested variations of up to 1.5 m in depth or 75% in porosity at any one time. Interannual variations in these data appeared to correlate with dust activity in the southern hemisphere. Correlation coefficients were used to investigate the relationship between frost-free surface properties and the evolution of the seasonal ice in this region. Ice on high thermal inertia units was found to disappear before any other ice, likely caused by inhibited deposition during fall. Seasonal ice springtime albedo appeared to be predominantly controlled by orientation, with north-facing slopes undergoing brightening initially in spring, then subliming before south-facing slopes. Overall, the state of seasonal ice is far more complex than globally and regionally averaged studies can identify.
The discovery of cryovolcanic features on Charon and the presence of ammonia hydrates on the surfaces of other medium-sized Kuiper Belt Objects suggests that cryovolcanism may be important to their evolution. A two-dimensional, center-point finite difference, thermal hydraulic model was developed to explore the behavior of cryovolcanic conduits on midsized KBOs. Conduits on a Charon-surrogate were shown to maintain flow through over 200 km of crust and mantle down to radii of R = 0.20 m. Radii higher than this became turbulent due to high viscous dissipation and low thermal conductivity. This model was adapted to explore the emplacement of Kubrik Mons. Steady state flow was achieved with a conduit of radius R = 0.02 m for a source chamber at 2.3 km depth. Effusion rates computed from this estimated a 122 - 163 Myr upper limit formation timescale.
The discovery of cryovolcanic features on Charon and the presence of ammonia hydrates on the surfaces of other medium-sized Kuiper Belt Objects suggests that cryovolcanism may be important to their evolution. A two-dimensional, center-point finite difference, thermal hydraulic model was developed to explore the behavior of cryovolcanic conduits on midsized KBOs. Conduits on a Charon-surrogate were shown to maintain flow through over 200 km of crust and mantle down to radii of R = 0.20 m. Radii higher than this became turbulent due to high viscous dissipation and low thermal conductivity. This model was adapted to explore the emplacement of Kubrik Mons. Steady state flow was achieved with a conduit of radius R = 0.02 m for a source chamber at 2.3 km depth. Effusion rates computed from this estimated a 122 - 163 Myr upper limit formation timescale.
ContributorsMount, Christopher (Author) / Christensen, Philip R. (Thesis advisor) / Desch, Steven J (Committee member) / Bell, James F. (Committee member) / Clarke, Amanda B (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2019
Description
Planetary mineralogy provides important clues about a planet’s geologic history, specifically how the planet first solidified and what geological processes have taken place since. I used spectral and composition data from the Mars Science Laboratory Curiosity rover to study some of the most recent geologic events on Mars. I also used modeled mineralogy of hypothetical exoplanets to understand the initial crystallization of exoplanets. Orbital data of Mt. Sharp, a ~5 km tall mound of sedimentary material, in Gale crater suggests that minerals associated with liquid water are present. These minerals, such as hydrated Mg-sulfates that are left behind as water evaporates, likely represent the beginning of Mars’ transition from a warm wet planet to the cold dry planet it is today.To understand how the mineralogy of Mt. Sharp changed, I used data from the Mastcam instrument on Curiosity to collect visible to near-infrared spectra of rocks from Vera Rubin Ridge and the Carolyn Shoemaker formation. Additionally, I collected laboratory spectra of powered binary mineral mixtures to understand how common minerals such as plagioclase, pyroxene, and hematite might obscure the spectral features of phyllosilicates and Mg-sulfates. Lastly, to better understanding Mars’ mineralogy, I analyzed numerous mixtures with Mg-sulfates in a nitrogen filled glovebox to better represent some of the environmental conditions of present-day Mars.
Minerals such as phyllosilicates and Mg-sulfates, often referred to as secondary minerals, are only found on planets that have experienced alteration since the planet first solidified. The current level of understanding of Martian mineralogy has only been obtained after decades of sending numerous orbital and landed missions with intricate science instruments. But there is not this level of understanding for all planets, and especially not for planets outside of the solar system. Using modeled mineralogy, I deciphered the order in which primary minerals (i.e., olivine, pyroxenes, and plagioclase) could have formed as exoplanets first solidified. Understanding the mineralogy of planetary bodies gives insight into the geologic history of processes that cannot be seen, because they are no longer occurring, or even of planets that are difficult to find.
ContributorsJacob, Samantha Renee (Author) / Bell Iii, James F (Thesis advisor) / Till, Christy B (Committee member) / Desch, Steven J (Committee member) / Robinson, Mark S (Committee member) / Williams, David A (Committee member) / Arizona State University (Publisher)
Created2022
Description
Planetary surfaces are constantly evolving through a series of endogenic and exogenic processes. Multi-temporal observations enable the detection of these newly formed surface changes. Analysis techniques of these observations require precise image geolocation obtainable only with accurate optical and projection distortion corrections. In this study, the Clementine Ultraviolet-Visible camera is geometrically calibrated, and the spacecraft orientation knowledge is refined, aligning the entire dataset to the reference frame defined by the more recent Lunar Reconnaissance Orbiter mission. This direct registration approach improved the geolocation to within 0.084 pixels (i.e., sub-pixel), enabling new optical maturity and mineral composition maps aligned with the present reference frame.Next, new surface changes on Mercury are discovered with a geometrically calibrated Mercury Dual Imaging Camera suite. Over twenty surface changes varying in size from 450 to 4400 meters are identified that formed between 2011 to 2015. Exogenic impacts do not explain all the surface changes witnessed. Some changes occurred on slopes near prominent tectonic features suggesting a potential tie to seismic activity. A pair of other reflectance changes were identified around hollow formations, meaning the surface feature is still evolving. This temporal dataset provides the first direct evidence of endogenic and exogenic activities of the innermost planet.
Lastly, the color and photometric properties of newly formed impact craters are explored using hundreds of observations acquired before and post-impact. These observations reveal new details about the distal surface changes associated with the impact process. Phase ratio imaging enables a measurement of the phase curve slope, including near opposition (phase ~ 0°). While the entire proximal ejecta blanket shows an increase in the optical surface roughness properties, the region adjacent to the crater rim (1.0 to 1.25 crater radii from the center) expresses a broadening of the opposition surge consistent with the presence of fine-scale surface particles and rocks. Finally, Hapke parameters and color maps are also derived for the entire region before and after the impact event to quantify changes in surface properties and the maturity state of the regolith. This work provides new insight into the broad extent of surface modifications around newly formed craters.
ContributorsSpeyerer, Emerson (Author) / Robinson, Mark S (Thesis advisor) / Bell, James F (Committee member) / Hervig, Richard L (Committee member) / Scowen, Paul A (Committee member) / Zolotov, Mikhail Y (Committee member) / Arizona State University (Publisher)
Created2023