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Description
Planetary surface studies across a range of spatial scales are key to interpreting modern and ancient operative processes and to meeting strategic mission objectives for robotic planetary science exploration. At the meter-scale and below, planetary regolith conducts heat at a rate that depends on the physical properties of the regolith particles, such as particle size, sorting, composition, and shape. Radiometric temperature measurements thus provide the means to determine regolith properties and rock abundance from afar. However, heat conduction through a matrix of irregular particles is a complicated physical system that is strongly influenced by temperature and atmospheric gas pressure. A series of new regolith thermal conductivity experiments were conducted under realistic planetary surface pressure and temperature conditions. A new model is put forth to describe the radiative, solid, and gaseous conduction terms of regolith on Earth, Mars, and airless bodies. These results will be used to infer particle size distribution from temperature measurements of the primitive asteroid Bennu to aid in OSIRIS-REx sampling site selection. Moving up in scale, fluvial processes are extremely influential in shaping Earth's surface and likely played an influential role on ancient Mars. Amphitheater-headed canyons are found on both planets, but conditions necessary for their development have been debated for many years. A spatial analysis of canyon form distribution with respect to local stratigraphy at the Escalante River and on Tarantula Mesa, Utah, indicates that canyon distribution is most closely related to variations in local rock strata, rather than groundwater spring intensity or climate variations. This implies that amphitheater-headed canyons are not simple markers of groundwater seepage erosion or megaflooding. Finally, at the largest scale, volcanism has significantly altered the surface characteristics of Earth and Mars. A field campaign was conducted in Hawaii to investigate the December 1974 Kilauea lava flow, where it was found that lava coils formed in an analogous manner to those found in Athabasca Valles, Mars. The location and size of the coils may be used as indicators of local effusion rate, viscosity, and crustal thickness.
ContributorsRyan, Andrew J (Author) / Christensen, Philip R. (Thesis advisor) / Bell, James F. (Committee member) / Whipple, Kelin X (Committee member) / Ruff, Steven W (Committee member) / Asphaug, Erik I (Committee member) / Arizona State University (Publisher)
Created2018
Description
Affect is a domain of psychology that includes attitudes, emotions, interests, and values. My own affect influenced the choice of topics for my dissertation. After examining asteroid interiors and the Moon’s thermal evolution, I discuss the role of affect in online science education. I begin with asteroids, which are collections of smaller objects held together by gravity and possibly cohesion. These “rubble-pile” objects may experience the Brazil Nut Effect (BNE). When a collection of particles of similar densities, but of different sizes, is shaken, smaller particles will move parallel to the local gravity vector while larger objects will do the opposite. Thus, when asteroids are shaken by impacts, they may experience the BNE as possibly evidenced by large boulders seen on their surfaces. I found while the BNE is plausible on asteroids, it is confined to only the outer layers. The Moon, which formed with a Lunar Magma Ocean (LMO), is the next topic of this work. The LMO is due to the Moon forming rapidly after a giant impact between the proto-Earth and another planetary body. The first 80% of the LMO solidified rapidly at which point a floatation crust formed and slowed solidification of the remaining LMO. Impact bombardment during this cooling process, while an important component, has not been studied in detail. Impacts considered here are from debris generated during the formation of the Moon. I developed a thermal model that incorporates impacts and find that impacts may have either expedited or delayed LMO solidification. Finally, I return to affect to consider the differences in attitudes towards science between students enrolled in fully-online degree programs and those enrolled in traditional, in-person degree programs. I analyzed pre- and post-course survey data from the online astrobiology course Habitable Worlds. Unlike their traditional program counterparts, students enrolled in online programs started the course with better attitudes towards science and also further changed towards more positive attitudes during the course. Along with important conclusions in three research fields, this work aims to demonstrate the importance of affect in both scientific research and science education.
ContributorsDingatantrige Perera, Jude Viranga (Author) / Asphaug, Erik (Thesis advisor) / Semken, Steven (Thesis advisor) / Anbar, Ariel (Committee member) / Elkins-Tanton, Linda T. (Committee member) / Robinson, Mark (Committee member) / Arizona State University (Publisher)
Created2017
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
There are more than 20 active missions exploring planets and small bodies beyond Earth in our solar system today. Many more have completed their journeys or will soon begin. Each spacecraft has a suite of instruments and sensors that provide a treasure trove of data that scientists use to advance our understanding of the past, present, and future of the solar system and universe. As more missions come online and the volume of data increases, it becomes more difficult for scientists to analyze these complex data at the desired pace. There is a need for systems that can rapidly and intelligently extract information from planetary instrument datasets and prioritize the most promising, novel, or relevant observations for scientific analysis. Machine learning methods can serve this need in a variety of ways: by uncovering patterns or features of interest in large, complex datasets that are difficult for humans to analyze; by inspiring new hypotheses based on structure and patterns revealed in data; or by automating tedious or time-consuming tasks. In this dissertation, I present machine learning solutions to enhance the tactical planning process for the Mars Science Laboratory Curiosity rover and future tactically-planned missions, as well as the science analysis process for archived and ongoing orbital imaging investigations such as the High Resolution Imaging Science Experiment (HiRISE) at Mars. These include detecting novel geology in multispectral images and active nuclear spectroscopy data, analyzing the intrinsic variability in active nuclear spectroscopy data with respect to elemental geochemistry, automating tedious image review processes, and monitoring changes in surface features such as impact craters in orbital remote sensing images. Collectively, this dissertation shows how machine learning can be a powerful tool for facilitating scientific discovery during active exploration missions and in retrospective analysis of archived data.
ContributorsKerner, Hannah Rae (Author) / Bell, James F. (Thesis advisor) / Ben Amor, Heni (Thesis advisor) / Wagstaff, Kiri L (Committee member) / Hardgrove, Craig J (Committee member) / Shirzaei, Manoochehr (Committee member) / Arizona State University (Publisher)
Created2019
Description
Meteorites and their components can be used to unravel the history of the early Solar System. Carbonaceous chondrites are meteorites that originated from undifferentiated parent bodies that formed within a few million years of the beginning of the Solar System. These meteorites contain calcium-aluminum-rich inclusions (CAIs), which are the oldest dated solids in the Solar System at ~4.567 billion years old and thus preserve a record of the earliest stage of Solar System formation. The isotopic compositions of CAIs and bulk carbonaceous chondrites can be used to identify the sources of material inherited by the protoplanetary disk, assess the degree of mixing in the disk, and evaluate sample origins and potential genetic relationships between parent bodies. In particular, mass-independent Cr and Ti isotopic compositions have proven to be especially useful for these purposes.
In this work, I first developed new methods for the chemical separation of Cr and Ti, improving the reliability of existing methods to ensure consistent yields and accurate isotopic measurements. I then measured the Cr and Ti isotopic compositions of CAIs from CV and CK chondrites to determine the extent of isotopic heterogeneity in the CAI-forming region and assess the role of CAIs in the preservation of planetary-scale isotopic anomalies. My results show that all measured CAIs originated from a common isotopic reservoir that incorporated material from at least three distinct nucleosynthetic sources and preserved limited isotopic heterogeneity. These results also suggest that planetary-scale isotopic anomalies cannot be attributed solely to the transport of CAIs from one part of the solar nebula to another. I finally measured the Cr and Ti isotopic compositions of bulk CM, CO, and ungrouped chondrites to evaluate the relationship between CM and CO chondrites, which have been suggested to originate from either distinct but related parent bodies or a common compositionally heterogeneous parent body. My results suggest that CM, CO, and related ungrouped chondrites originated from distinct parent bodies that formed from similar precursor materials in nearby formation regions. These results may have implications for asteroid samples returned by the OSIRIS-REx and Hayabusa2 missions.
In this work, I first developed new methods for the chemical separation of Cr and Ti, improving the reliability of existing methods to ensure consistent yields and accurate isotopic measurements. I then measured the Cr and Ti isotopic compositions of CAIs from CV and CK chondrites to determine the extent of isotopic heterogeneity in the CAI-forming region and assess the role of CAIs in the preservation of planetary-scale isotopic anomalies. My results show that all measured CAIs originated from a common isotopic reservoir that incorporated material from at least three distinct nucleosynthetic sources and preserved limited isotopic heterogeneity. These results also suggest that planetary-scale isotopic anomalies cannot be attributed solely to the transport of CAIs from one part of the solar nebula to another. I finally measured the Cr and Ti isotopic compositions of bulk CM, CO, and ungrouped chondrites to evaluate the relationship between CM and CO chondrites, which have been suggested to originate from either distinct but related parent bodies or a common compositionally heterogeneous parent body. My results suggest that CM, CO, and related ungrouped chondrites originated from distinct parent bodies that formed from similar precursor materials in nearby formation regions. These results may have implications for asteroid samples returned by the OSIRIS-REx and Hayabusa2 missions.
ContributorsTorrano, Zachary (Author) / Wadhwa, Meenakshi (Thesis advisor) / Anbar, Ariel D (Committee member) / Schrader, Devin L (Committee member) / Williams, David A. (Committee member) / Young, Patrick A (Committee member) / Arizona State University (Publisher)
Created2020
Description
Jupiter’s moon Io is tidally locked with Jupiter and falls in a 4:2:1 orbital
resonance with Europa and Ganymede, driving extreme tidal heating that makes it the most volcanically active body in the solar system. Io possesses a metallic core, as does its Galilean sibling Ganymede, yet, unlike Ganymede, Io lacks a magnetic field. Here, I investigated the potential size, composition, and cooling rate of Io’s core to help determine why Io lacks a strong dynamo. First, I used mineral physics equations to determine that the radius of the core should be between ~650 km to 950 km for a composition ranging from pure Fe to a eutectic Fe-FeS alloy. Cosmochemical constraints from meteoritic analogues yield complementary constraints on the abundance of sulfur in the metallic core (~2.67–28.6 wt%). The mantle could be either fully or partially molten. I found that the scenario of a global magma ocean creates temperatures at the base of the mantle that are possibly too hot for core convection, but that a magma sponge regime could create core-mantle boundary temperatures cooler than the melting point of pure Fe, which could promote core convection. Therefore, I conclude that Io lacks a strong dynamo likely because it has a magma ocean with temperatures too high for convection. However, the possibility that Io’s mantle is a magma sponge suggests the importance for future missions to investigate the state of Io’s magnetic field.
ContributorsLunetto, Sarah (Author) / O'Rourke, Joseph (Thesis director) / Walker, Sara (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2024-05