Browsing by Subject "Mars"
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Item Aeolian dune dynamics and the stratigraphic record(2016-12) Brothers, Sarah Christian; Kocurek, Gary; Byrne, Shane; Hern, Caroline; Holt, John; Mohrig, DavidDunes and dune fields are dynamic features that respond to the unique boundary conditions under which they evolve by changing migration habits, types and frequencies of interactions, and morphologies. As such, dunes convey information about changing atmospheric and surface conditions on planetary bodies including Earth, Mars, Venus, and Titan, and the stratigraphic record left by these bedforms is used to interpret the evolution of paleoclimate and surface environments. In four parts this work examines how the dynamics of individual dunes, dune fields, and aeolian systems influence stratigraphic architectures across multiple spatial scales. At White Sands Dune Field, New Mexico, the decadal histories of defect and bedform repulsion-type interactions are traced through a time-series of images. The resultant stratigraphic architectures are derived from plan-view exposures and ground penetrating radar sensing of dune interiors. This is the first documentation of the unique stratigraphic architectures that result from interactions between dunes. Within Chasma Boreale, Planum Boreum, Mars, boundary conditions controlling the discrete geomorphic expressions of the Hyperboreae Undae dune fields are evaluated using morphologic distributions. The distributions reveal that dune field expressions change over short horizontal scales and are dependent upon wind regime and sediment state, which operate under the background condition of dune induration by ice. Hyperboreae Undae form only part of the Chasma Boreale sediment system, however. Perennial layered ice deposits also are present on the floor of the reentrant. The changing balance of ice- and sand-dominated processes in space and time have resulted in an accumulation that transitions between ancient aeolian cavi unit-style accumulation and modern layered ice deposit-style accumulation. These accumulations can be interpreted through aeolian sequence stratigraphy. Findings from the Chasma Boreale transitional sediment system are applied to nearby outcrops of a transitional section of ancient cavi unit, which formed in an environment analogous to the modern Chasma Boreale sediment system. A sequence interpretation of the transitional cavi unit stratigraphic succession demonstrates how the aeolian system transitioned into overlying water ice deposits without a gap in the geologic record, verifying that the cavi unit and NPLD should be unified under a sequence stratigraphic framework.Item Aeolian dune-field boundary conditions and dune interactions related to dune-field pattern formation on Earth and Mars(2009-12) Ewing, Ryan Cotter; Kocurek, GaryAeolian dune fields form some of the most striking patterns on Earth and Mars. These patterns reflect the internal dune dynamics of self-organization within boundary conditions, which are the unique set of environmental variables within which each dune field evolves. Dune-field pattern self-organization occurs because of interactions between the dunes themselves and the rich diversity of dune-field patterns arises because boundary conditions alter the type and frequency of dune interactions. These hypotheses are explored in three parts. First, source-area geometry and areal limits are two newly recognized boundary conditions. Measurements of crest length and spacing from satellite images of dune patterns with point and line source-area geometries show an increase in crest length and spacing over distance, whereas crest length and spacing in plane-sourced patterns emerge equally across the dune field. The areal limit boundary condition is the size and shape of the dune field itself. Empirical measurements from ten dune fields ranging over four orders of magnitude in area show that spacing increases and defect density decreases as the area of the dune field increases. A simple analytical model indicates that dune fields that are five times longer in the dune migration direction can achieve the greatest spacing for a given area. Second, time-series aerial photographs and airborne LiDAR show that fully developed, crescentic aeolian dunes at White Sands, New Mexico, interact and the dune pattern organizes in systematically similar ways as wind ripples and subaqueous dunes and ripples. Interaction type, classified as constructive, regenerative or neutral in terms of pattern development, changes spatially with the pattern because of the imposition of the line-source area and sediment availability boundary conditions. Upwind dominance by constructive interactions at the field line-source yields to neutral and regenerative interactions in the sediment availability-limited field center. Third, the dune-field pattern in the Olympia Undae Dune Field on Mars is comprised of two generations of dunes. This scenario of pattern reformation with a new wind regime shows that the emergence of the younger pattern is controlled by the boundary condition of the antecedent dune topography imposed upon the interaction between the younger and older patterns.Item Distribution and characteristics of boulder halos at high latitudes on Mars: ground ice and surface processes drive surface reworking(2017-12-04) Levy, JosephBoulder halos are circular arrangements of clasts present at martian middle to high latitudes. Boulder halos are thought to result from impacts into a boulder-poor surficial unit that is rich in ground-ice and/or sediments and that is underlain by a competent substrate. In this model, boulders are excavated by impacts and remain at the surface as the crater degrades. To determine the distribution of boulder halos and to evaluate mechanisms for their formation, we mapped boulder halos over 4,188 HiRISE images located between 50-80° north and south latitude. We evaluate geological and climatological parameters at halo sites. Boulder halos are about three times more common in the northern hemisphere than in the southern (19% vs. 6% of images), and have size-frequency distributions suggesting recent Amazonian formation (tens to hundreds of millions of years). In the north, boulder halo sites are characterized by abundant shallow subsurface ice and high thermal inertia. Spatial patterns of halo distribution indicate that excavation of boulders from beneath non-boulder-bearing substrates is necessary for the formation of boulder halos, but that alone is not sufficient. Rather, surface processes either promote boulder halo preservation in the north or destroy boulder halos in the south. Notably, boulder halos predate the most recent period of near-surface ice emplacement on Mars and persist at the surface atop mobile regolith. Finally, larger minimum boulder halo sizes in the north indicate thicker icy soil layers on average throughout climate variations driven by spin/orbit changes during the last 10s to 100s Ma.Item Evidence for changes in coastline-controlled base level from fluvial stratigraphy at Aeolis Dorsa, Mars(2014-12) Cardenas, Benjamin Thomas; Mohrig, David; Kocurek, GaryThere is evidence that a subset of fluvial deposits at Aeolis Dorsa, a basin on Mars, preserve incised valleys carved and filled during changes in base level, which was likely controlled by water surface elevation of a large lake or sea. Three low-albedo, channelized corridors, each several tens of kilometers long, contain relict point bars and scooped boundaries at their bases, indicating that the base and lateral extent of each corridor was defined by a migrating, net-erosional river. Above the basal deposits are stacks several tens of meters thick of “inverted sinuous ridges”, which are channel-filling deposits that have been exhumed and topographically inverted. Indicators of avulsions, channel re-occupations, an overall flattening of basal topography, and confinement of inverted sinuous ridges to the dark corridors are evidence of the gradual filling of a valley cut by the basal migrating river. Valley incision and fill are common responses to sea level change on Earth. Aeolis Dorsa is currently open to the northern lowlands of Mars, where an ocean has been hypothesized to have once existed, although a large lake could have also controlled base level. Cross-cutting valleys require at least two episodes of base level fall and rise. The magnitudes of the base level changes are estimated at about 80 meters, based on the thickness of the valley-filling stratigraphy. Meander asymmetry is consistent with a southeastern flow direction, and is supported by a set of branching fluvial deposits 40 km to the southeast which, qualitatively, appear to be deltaic in origin.Item Mars north polar ice stratigraphy project : a curriculum module for 5th grade(2011-08) Chavez, Augustine Faustino; Holt, John W., Ph.D.; Wilson, Clark R.This report is explores the need for a curriculum module for late elementary school students by looking at what drives student interests and motivations in pursuing careers in the sciences. The curriculum module created is composed of visual aids, including video animations, a 3-D scale model, and a hands-on, guided classroom activity. Exploring the stratigraphy on Mars Planum Boreum northern polar ice cap using radargrams from the Mars Reconnaissance Orbiter and modeling sublimation of Carbon Dioxide with a dry ice experiment, the curriculum module will be tested and improved upon over the next academic year in a 5th grade classroom with intent for submission to NASA for funding and eventual dissemination to the general public. The goal of the project is to add new, engaging dimensions to space science activities and to understanding of fundamental geologic principles, using real-time applications to foster interest and motivate students to enter the fields of the geosciences in the future.Item Mass balance of Martian sedimentary fans and valleys(2016-05-20) Shover, Katherine Rose; Holt, John W., Ph. D.; Kim, Wonsuck; Moscardelli, LorenaDozens of sedimentary fans have been identified on Mars and have been interpreted as alluvial fans or deltas. However, the extent to which these deposits represent the complete eroded mass of the valleys that drain into them, the extent to which erosion has removed fan material, and the extent to which sediment bypass occurred during fan deposition into a distal water body remain unknown. This study investigates the role of emplacement versus modification following deposition in a catalog of martian fans to determine the extent to which such deposits have been preserved. A mass balance approach was taken; by calculating the present volumes of fans and the valleys feeding them, the percentage of eroded valley sediment that has accumulated and remained within the fan deposits can be determined. Based on measurements of 32 valley and fan volumes calculated using CTX stereo DEMs, we find two major classes of landforms: isolated inlets with lower stream orders and fans of approximately equal volume to the source valleys, and regionally-integrated valley networks with higher stream orders and much smaller fan volumes than valley volumes. If stream order correlates with valley age on Mars, then these results imply change in martian erosion and deposition patterns over time. We infer that hydrodynamic sorting in older, wetter systems resulted in preferential deposition of fines in fans formed by higher stream order valleys, and, ultimately more erosion in these fine-grained deposits, while younger, drier systems created deposits with intermixed sediment sizes that remain preserved today due to the greater protection of the fines from post-depositional erosion. These observations are consistent with a waning hydrologic cycle throughout martian history.Item Morphology of the Planum Boreum basal unit, Mars, and constraints on the origin and timing of icy circumpolar deposits(2015-05) Brothers, Thomas Charles; Holt, John W., Ph. D.; Wood, Lesli J; Tanaka, Kenneth; Kocurek, Gary A; Mohrig, DavidData from the Shallow Radar instrument on Mars Reconnaissance Orbiter have enabled detailed scientific exploration of martian ice. Orbital ground penetrating radar enabled scientists to study subsurface ice stratigraphy, to uncover the geologic structure of ice on Mars with remarkable results for the north pole. On the north pole of Mars sits a massive, approximately two kilometer thick, deposit of pure water ice. This deposit is underlain with a sand and ice mixture that reaches 1.5 km maximum thickness. This dissertation examines the nature of the old sand/ice mixture on Mars' north pole. We use this ice to identify early trends in deposition and erosion on Mars' north pole and ultimately to link ice rich deposits that are not part of the polar cap. This multi-part study endeavors to understand and constrain the drivers of Mars' polar ice deposition. With careful stratigraphic analysis we hypothesize that depositional regime has not changed drastically since the upper part of the sand and ice mixture was emplaced in Middle Amazonian time. Sediment supply became limited and ice more plentiful with respect to sand; however, deposition remained aeolian in nature. Additionally, our work finds evidence that circumpolar landforms are related to the central mass of ice on Planum Boreum. We present evidence supporting a coeval evolution of the circumpolar deposits and central Planum Boreum. We also present evidence that refutes these features being part of a more extensive ancient ice cap. This indicates that the processes occurring at Planum Boreum are likely mirrored in nearby landforms such as small craters and isolated ice wedges. This is fundamental to polar science, the processes occurring on Planum Boreum and the processes responsible for deposition of the north polar layered deposits can be analyzed at additional locations. Furthermore, we find that if a climate signal exists in the ice deposits, as has been postulated, these circumpolar features are likely to contain the same climate signal as the central ice cap. Thus, this work unifies the complexity of martian polar processes and suggests future avenues of research.Item Motivation, Feasibility, and Ethics of Colonizing Mars(2021) Kolli, Divya; Hoffman, David W.Space exploration has excited Americans since the Space Race in the 1950s, which led to humans first stepping foot on the Moon in 1969. The next goal in space exploration is to send humans to Mars, which is driven by scientific interest and the current advancing climate change, overpopulation, and resource depletion of Earth. The potential habitability of Mars makes the planet more amenable than other planets in our solar system for supporting human life, which private companies claim will allow humans to successfully colonize the planet. However, many scientists and ethicists have stated that a pioneering population will face new obstacles in the journey and life on Mars. These hurdles are examined through a literature review focused on the feasibility of a successful colonization, human health in space, and the ethics of space colonization. Space sciences are highly affected by political tensions between technologically developed countries which will likely impact the sociopolitical structure and success of a long-term Martian colony. The pioneering population will also face dangers to their health from the isolation, microgravity, and radiation of space. Lastly, colonization of Mars will lead to the eventual environmental damage of the planet, which is both a scientific and ethical dilemma. The political, scientific, and ethical concerns that are currently unanswered outweigh arguments in support of Martian colonization. To protect the future pioneering population and the environmental health of Mars, these concerns must be mitigated by space agencies before developing the technology needed to send humans to colonize Mars.Item On the spiral troughs of Mars(2013-08) Smith, Isaac Blaine; Holt, John W., Ph. D.The north and south polar layered deposits (NPLD and SPLD respectively) of Mars are 2 – 3 km thick and mostly ice, comprising nearly all of the known water reserves on Mars. They are commonly believed to hold a detailed record of recent (~10 – 100 Myr) climate within their layers. Dominating the surface of the NPLD, intriguing spiral depressions called troughs, exhibit a pinwheel appearance. In late 2006, the Shallow Radar (SHARAD) instrument began making observations. SHARAD can detect internal structure within the PLD, making observations that are impossible with instruments that only inspect the surface. SHARAD data reveals a unique stratigraphic record associated with trough formation and migration. The troughs did not exist during deposition of the first half of NPLD accumulation but initiated some 1000 m below the current surface and have migrated as much as 100 km northward. Three processes are responsible for this migration: wind transport, insolation induced sublimation, and atmospheric deposition. I synthesize work from ground penetrating radar, optical imagery, established analogs, and atmospheric modeling in order to derive a process model that describes trough formation and evolution, including migration. The NPLD spiral troughs belong to a larger classification of features called cyclic steps, which can exist in either erosional or depositional environments. On the SPLD, troughs and a variety of other features exist. While SPLD features are more complex than NPLD troughs, they exist due to the same three processes.Item Pattern formation and preservation in aeolian systems(2017-05-02) Day, Mackenzie Denali; Kocurek , Gary; Mohrig, David; Holt, John; Kim, Wonsuck; Anderson , WilliamAeolian sediment transport forms natural patterns common on Earth and other planetary bodies. The self-organization of sand in transport results in dune fields with dune morphologies determined by wind regime. Patterning in dune fields is known to arise from the autogenic process of dune interactions, but the evolution of dune patterns over time remains poorly constrained. In this work dune fields were parameterized in terms of dune interactions to quantify dune-field pattern stability. Interactions are fundamental to dune-field development, but studies of interactions have focused on their surface expression, and how interactions are expressed in the ancient record has yet to be documented. This problem is addressed with five examples of interaction-generated stratigraphy identified in well-known Jurassic aeolian sandstones using criteria based on recent near-surface interpretations of interaction stratigraphy form White Sands Dune Field, New Mexico. Interactions control the autogenic development of dune fields, but allogenic factors including basin subsidence, water table rise, and sediment supply largely control the accumulation and preservation of aeolian strata. In a case study of a section of the Jurassic Entrada Sandstone, this work addresses the interplay between allogenic and autogenic controls on what is actually preserved in the rock record, and demonstrates how long stretches of time can be collapsed into surfaces between geologic units that represent relatively short-lived events. The competition between allogenic and autogenic influences on aeolian pattern formation is not unique to Earth, and Mars also hosts patterned landscapes thought to be generated by aeolian sediment transport. Such landscapes include intra-crater layered mounds such as Aeolis Mons in Gale crater, the landing site of the Mars Science Laboratory rover. Competing hypotheses about whether these mounds formed by aeolian erosion of crater-filling deposits, or by aeolian deposition were addressed with wind tunnel and large eddy simulation experiments. The results are compatible with an erosional origin of the mounds. Additional analyses of wind-formed landscapes within and around Gale crater further supported the wind-erosion hypothesis of the central mound.Item Presentation: Curiosity’s First Year of Exploration on Mars(Environmental Science Institute, 2016-10-18) Grotzinger, John; Environmental Science InstituteItem Presentation: Icy Mysteries of Mars Revealed(Environmental Science Institute, 2009-09-11) Environmental Science Institute; Holt, John "Jack"Item Ridges on martian debris-covered glaciers : deconvolving structural and climate processes(2017-05-12) Stuurman, Cassie; Holt, John W; Levy, Joe SDebris-covered glaciers on Earth and Mars often exhibit surface ridges transverse to the flow direction of the glacier. The formation mechanism of these ridges is not well established, but some evidence from terrestrial analogues supports the idea that surface ridges may demarcate climate cycles. It is also possible they are induced by thrust faulting, buckle folding, or other compressional mechanisms. This work aims to differentiate climate-related ridges from thrust fault and buckle folding ridges on Mars through mapping, geometric analysis, and flow modelling. We find that martian glaciers exhibit ridges of a variety of amplitudes and wavelengths. Large ridges on martian debris-covered glaciers cannot be explained by buckle folding given their long arclengths and inconsistent inter-ridge spacing, while some smaller ridges are consistent with the expected arclengths for buckle folds on Mars. The smaller ridges also exhibit highly consistent inter-ridge spacing and morphologies similar to terrestrial examples of two-layer buckle folds. Flow modelling results suggest that thrust faulting is a possible explanation for ridges on some debris covered glaciers, but thrust faulting diminishes as temperature decreases. We conclude that it some ridges on martian debris-covered glaciers are likely caused by climate variations however the buckle folding hypothesis is plausible for finely spaced ridges.Item Shield volcanoes(2009-03) Barker, Daniel S.Item Surface boulder banding indicates martian debris-covered glaciers formed over multiple glaciations(2020) Levy, JosephGlacial landforms including lobate debris aprons are a globally distributed water ice reservoir on Mars preserving ice from past periods when high orbital obliquity permitted non-polar ice accumulation. Numerous studies have noted morphological similarities between lobate debris aprons and terrestrial debris-covered glaciers, an interpretation supported by radar observations. On both Earth and Mars, these landforms consist of a core of flowing ice covered by a rocky lag. Terrestrial debris-covered glaciers advance in response to climate forcing, driven by obliquity-paced changes to ice mass balance. However, on Mars, it is not known whether glacial landforms that were emplaced over the past 300-800 Ma formed during a single, long deposition event or during multiple glaciations. Here we show that boulders atop 45 lobate debris aprons exhibit no evidence of sequential comminution, but are clustered into bands that become more numerous with increasing latitude, debris apron length, and pole-facing flow orientation. Boulder bands are prominent at glacier headwalls, consistent with debris accumulation during the current martian interglacial. Terrestrial debris-covered glacier boulder bands occur near flow discontinuities caused by obliquity-driven hiatuses in ice accumulation that form internal debris layers. By analogy, we suggest that martian lobate debris aprons experienced multiple cycles of ice deposition, followed by destabilization of ice in the accumulation zone leading to boulder-dominated lenses, and subsequent ice deposition and continued flow. Correlation between latitude and boulder clustering suggests that ice mass balance works across global scales on Mars. Individual lobate debris aprons may preserve ice spanning multiple glacial/interglacial cycles.Item The ice content and internal structure of candidate debris-covered glaciers on mars and earth : insights from radar sounding(2018-09-13) Petersen, Eric Ivan; Holt, John W., Ph. D.; Levy, Joseph S.; Catania, Ginny; Grima, Cyril; Mohrig, DavidMartian lobate debris aprons are enigmatic mid-latitude landforms known to contain a significant fraction of water ice preserved at depth beneath a surface debris layer. They are thought to be important records of climate history and potential water resources for manned missions to Mars. However, their internal structure remains poorly constrained and regional variability in their ice purity is unknown. In this dissertation we report on a regional orbital radar sounding survey of lobate debris aprons in Deuteronilus Mensae – the region of highest concentration of lobate debris aprons on Mars – to constrain trends in lobate debris apron composition and possible internal structure. We also present a geophysical survey of Galena Creek Rock Glacier to constrain its internal structure as an analog to Martian lobate debris aprons. We found that the majority of radar observations imaged a basal reflector, from which we determined that the apron body is composed of material with dielectric properties consistent with relatively pure water ice and that there is no evidence for region-wide variability. Combining our compositional results with apron volumes constrained by Levy et al. (2014) sets the regional ice budget at 0.9-1.0 x 10⁵km³, the equivalent of roughly 4x the combined volume of water in the Great Lakes. We additionally showed that non-detection of basal reflectors in 13% of the observations may be attributed to high apron thickness and surface roughness-induced signal loss. In our analog work on Galena Creek Rock Glacier, we imaged its internal structure consisting of a network of englacial debris layers. This internal structure is indicative of intermittent debris and ice accumulation, with debris fall potentially playing a role in enhancing and facilitating ice accumulation. Similar englacial debris layers may exist in Martian lobate debris aprons, but are not imaged by the available orbital radar dataset due to their dip and thickness.Item Unraveling the morphological and stratigraphic signature of global climate events within the Planum Boreum of Mars(2019-08-12) Nerozzi, Stefano; Holt, John W., Ph. D.; Levy, Joseph S; Putzig, Nathaniel E; Kocurek, Gary A; Mohrig, DavidPlanum Boreum (PB) is a dome of layered icy material rising ~3 km above the surrounding plains in the northern hemisphere of Mars, and is divided into two main units: the lithic-rich basal unit (BU) and the overlying water ice-rich north polar layered deposits (NPLD). Since their discovery, the rich stratigraphic record of the NPLD has long been regarded as the key for understanding the most recent climate evolution of Mars and its dependency on periodical variations of Mars’ orbital parameters. The emplacement of the NPLD represents a major, global-scale shift of water ice on Mars, likely driven by climate change, yet the reasons and time scale for this event are still unknown. Similarly, the underlying BU likely recorded polar geologic processes and global climate in the Amazonian Period (3 Ga until present) in its strata and morphology, yet this unit remains largely unexplored. This is primarily due to limited outcrops of the lowermost NPLD and the underlying BU, as well as an incomplete understanding of the role of polar geologic processes in the context of global climate change. The large amount of remote sensing data acquired in recent years opens the possibility to better decipher the geologic record of PB with an integrated approach that couples radar sounding, high-resolution visible imagery and general circulation modeling. In this dissertation, I present three studies that take advantage of the extremely dense and extensive coverage of radar data over PB to map the lowermost NPLD and uppermost BU in their entirety, and integrate these with analysis of newly acquired high-resolution visible imagery of the BU-NPLD contact to reconstruct the transitional environment between the two units in great detail. These studies provide the observational constraints necessary to run general circulation models specifically tuned to the north polar region of Mars, and test their sensitivity to predicted Mars’ varying orbital parameters. This approach has the unique potential to determine which driving forces and geologic processes are responsible for the initial emplacement of the largest water ice reservoir in the northern hemisphere of Mars.Item Use of raw Martian and Lunar soils for surface-based reactor shielding(2010-12) Christian, Jose L. 1963-; Landsberger, SheldonFor several decades, the idea of flying and landing a less-than-man-rated nuclear reactor for planetary surface applications has been considered. This approach promises significant mass savings and therefore reduction in launch cost. To compensate for the lack of shielding, it has been suggested the use of in-situ materials for providing radiation protection. This would take the form of either raw dirt walls or processed soil materials into blocks or tile elements. As a first step in determining the suitability of this approach, it is necessary to understand the neutron activation characteristics of these soils. A simple assessment of these activation characteristics was conducted for both Martian and Lunar soils using ORIGEN2.2. An average composition for these soils was assumed. As a baseline material, commonly used NBS-03 concrete was compared against the soils. Preliminary results indicate that over 2.5 times more gamma-radiation production of these soils vs. concrete took place during the irradiation phase (a baseline of 2.4 x 1011 neutrons/sec-cm2 was assumed). This was due primarily to radiative capture on Na23 and Mn55 and subsequent decay of their activation products. This is does not necessarily disqualify these materials as potential shielding material since the -radiation output was only in the order of 4.2 x 108 photons/cm3-sec. Furthermore, these soils did not show any significant activity after shutdown of the neutron source (the reactor), since all activation products had very short half lives. Their performance in this area was comparable to that of NBS-03 concrete.Item Using radar reflectivity to unlock the climate record contained in the Martian North Polar Layered Deposits(2017-08-04) Lalich, Daniel E; Holt, John W., Ph. D.; Levy, Joseph; Grima, Cyril; Catania, Ginny; Kocurek, GaryThe North Polar Layered Deposits of Mars are a formation of water ice ~1000 km across and ~2 km thick. For years, scientists have looked to these layers of ice and dust as a possible source of information regarding how the planet’s climate has changed over the past ~4 million years. However, connecting these layers to specific climate conditions remains a challenge. Previous research has attempted to tie both radar stratigraphy and outcrop stratigraphy to the orbital cycles of Mars, but the proposed relationships are often contradictory, and struggle identify how specific layer properties might be tied to ancient climate. To help resolve these issues, I synthesized a combination of SHARAD radar data, HiRISE imagery, topography, and electromagnetic modeling in an effort to quantify layer properties such as thickness and composition, and connect those properties to past climate conditions. I was able to quantitatively show that a set of layers known as marker beds is likely responsible for causing radar reflectors, and was able to show how radar reflectors could be used to infer the composition and relative thickness of these layers throughout the polar cap. With this information in hand, scientists can, for the first time, begin to realize the full potential of the North Polar Layered Deposits as a global climate record of Mars.Item Will we live on Mars?(2020-11-06) Levy, Joe