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- All Subjects: Mars
- Creators: Robinson, Mark S
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
Remote sensing in visible to near-infrared wavelengths is an important tool for identifying and understanding compositional differences on planetary surfaces. Electronic transitions produce broad absorption bands that are often due to the presence of iron cations in crystalline mineral structures or amorphous phases. Mars’ iron-rich and variably oxidized surface provides an ideal environment for detecting spectral variations that can be related to differences in surface dust cover or the composition of the underlying bedrock. Several imaging cameras sent to Mars include the capability to selectively filter incoming light to discriminate between surface materials.
At the coarse spatial resolution provided by the wide-angle Mars Color Imager (MARCI) camera aboard the Mars Reconnaissance Orbiter (MRO), regional scale differences in reflectance at all wavelengths are dominated by the presence or absence of Fe3+-rich dust. The dust cover in many regions is highly variable, often with strong seasonal dependence although major storm events can redistribute dust in ways that significantly alter the albedo of large-scale regions outside of the normal annual cycle. Surface dust reservoirs represent an important part of the martian climate system and may play a critical role in the growth of regional dust storms to planet-wide scales. Detailed investigation of seasonal and secular changes permitted by repeated MARCI imaging coverage have allowed the surface dust coverage of the planet at large to be described and have revealed multiannual replenishing of regions historically associated with the growth of storms.
From the ground, rover-based multispectral imaging acquired by the Mastcam cameras allows compositional discrimination between bedrock units and float material encountered along the Curiosity rover’s traverse across crater floor and lower Mt. Sharp units. Mastcam spectra indicate differences in primary mineralogy, the presence of iron-bearing alteration phases, and variations in iron oxidation state, which occur at specific locations along the rover’s traverse. These changes represent differences in the primary depositional environment and the action of later alteration by fluids circulating through fractures in the bedrock. Loose float rocks sample materials brought into the crater by fluvial or other processes. Mastcam observations provide important constraints on the geologic history of the Gale Crater site.
At the coarse spatial resolution provided by the wide-angle Mars Color Imager (MARCI) camera aboard the Mars Reconnaissance Orbiter (MRO), regional scale differences in reflectance at all wavelengths are dominated by the presence or absence of Fe3+-rich dust. The dust cover in many regions is highly variable, often with strong seasonal dependence although major storm events can redistribute dust in ways that significantly alter the albedo of large-scale regions outside of the normal annual cycle. Surface dust reservoirs represent an important part of the martian climate system and may play a critical role in the growth of regional dust storms to planet-wide scales. Detailed investigation of seasonal and secular changes permitted by repeated MARCI imaging coverage have allowed the surface dust coverage of the planet at large to be described and have revealed multiannual replenishing of regions historically associated with the growth of storms.
From the ground, rover-based multispectral imaging acquired by the Mastcam cameras allows compositional discrimination between bedrock units and float material encountered along the Curiosity rover’s traverse across crater floor and lower Mt. Sharp units. Mastcam spectra indicate differences in primary mineralogy, the presence of iron-bearing alteration phases, and variations in iron oxidation state, which occur at specific locations along the rover’s traverse. These changes represent differences in the primary depositional environment and the action of later alteration by fluids circulating through fractures in the bedrock. Loose float rocks sample materials brought into the crater by fluvial or other processes. Mastcam observations provide important constraints on the geologic history of the Gale Crater site.
ContributorsWellington, Danika (Author) / Bell Iii, James F (Thesis advisor) / Christensen, Philip R. (Committee member) / Robinson, Mark S (Committee member) / Sharp, Thomas G (Committee member) / Till, Christy B. (Committee member) / Arizona State University (Publisher)
Created2018
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