Geology topics

Amber L. Gullikson

Publications and source records attributed to Amber L. Gullikson.

14 recordsLinked to original sources

USGS2026

Phase evolution and elemental partitioning in impact melts from Meteor Crater, Arizona

The impact of the Canyon Diablo iron meteorite in Arizona ∼61,000 years ago resulted in partial vaporization of the meteorite and target rocks, producing a vapor plume and melt particles with taenite, olivine and clinopyroxene in glassy matrix. The resulting Meteor Crater is ∼1.2 km in diameter and ∼200 m deep. Although the crater has been the natural laboratory for impact cratering, the microstructure and composition of its impact-melt particles remain poorly studied. Here microstructure and composition were investigated using optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction, and synchrotron microdiffraction on particles collected from the ejecta blanket to reconstruct their temporal and mineralogical evolution during ultrafast quenching and to explore how mafic minerals form from sedimentary-derived melts. Elemental mapping reveals complex chemical partitioning among glass and mafic phases. Formation of Fe-Ni globules with face-centered cubic (fcc) taenite indicates oxygen fugacity well below atmospheric in the vapor cloud. During rapid cooling, skeletal olivine crystallized, followed by nucleation of clinopyroxenes to form spherical clusters. The glassy matrix contains two glasses separated by sharp boundaries, likely representing immiscible melts derived from different lithologies. The hot particles were deposited on the surface among quartz- and dolomite-rich ejecta, followed by post-depositional precipitation of calcite and barite within glassy nodules. The results demonstrate that mafic minerals can crystallize from melts derived largely from sedimentary target rocks, with Fe supplied by the impactor, and that elemental partitioning and mineral textures record strong disequilibrium crystallization during rapid cooling.

Arizona↗

USGS2026

Lunar analog study using portable gamma-ray neutron detector: Radiochemical mapping of silicic-to-basaltic volcanic terrains in the San Francisco Volcanic Field, Arizona

Studying lunar silicic volcanism provides key insights into the Moon’s crustal evolution, magmatic processes, and volcanic history. The Lunar-VISE (Lunar Vulkan Imaging and Spectroscopy Explorer) mission will investigate the Gruithuisen domes, a unique lunar region hypothesized to have formed through silicic volcanism. Using instruments on a Firefly Aerospace lander and a Honeybee Robotics rover, Lunar-VISE will analyze mineralogy, geochemistry, and surface properties to determine the origin and evolution of the domes, with a gamma-ray and neutron spectrometer (LV-GRNS) among its payload instruments. In preparation for this mission, we conducted preliminary fieldwork using a handheld gamma-ray neutron detector with NaI(Tl) and Cs LiYCl :Ce (CLYC) scintillators. This study focuses on various rhyolitic and basaltic volcanic centers in the San Francisco Volcanic Field (SFVF) near Flagstaff, Arizona—specifically Sugarloaf Peak, Bonito Lava Flow, and Robinson Mountain, a region containing several well-characterized lunar analog sites. The SFVF was selected for this study due to its broad compositional diversity spanning basaltic to rhyolitic compositions, its well-preserved volcanic morphologies, and its extensive use in previous NASA field campaigns and astronaut training exercises, making it an ideal terrestrial laboratory for testing planetary exploration techniques. We measured natural radioactivity, specifically from potassium (K), thorium (Th), and uranium (U) and other elements in their decay chains, which serve as diagnostic tracers of magmatic differentiation and crustal evolution processes, to assess geochemical variability across compositionally diverse terrains. The detector’s sensitivity was assessed across varying concentration levels. Regionally averaged concentrations of radioisotopes were determined by gamma-ray spectroscopy at selected sites. Our measurements reveal significant compositional variations between sites, with Sugarloaf Peak (rhyolitic, silicic dome) exhibiting the highest average radioisotope concentrations (K: 3.29 ± 0.24 wt%, U: 14.35 ± 1.81 ppm, Th: 27.14 ± 2.43 ppm), while Bonito Lava Flow (K: 1.13 ± 0.08 wt%, U: 3.86 ± 0.52 ppm, Th: 7.52 ± 1.02 ppm), and Robinson Mountain (K: 1.46 ± 0.16 wt%, U: 5.59 ± 1.06 ppm, Th: 11.75 ± 1.98 ppm) show lower concentrations aligned with basaltic compositions. Gamma-ray fluxes were elevated by a factor of approximately three to four at Sugarloaf Peak relative to nearby basaltic terrains, consistent with expected geochemical differentiation patterns. Furthermore, at meter scales, proximity to geological features significantly affects measurements. Th concentrations adjacent to a cliff face at Sugarloaf’s base were 28% higher than values measured 3-5 meters away from the same feature, demonstrating localized compositional heterogeneity. Analysis of station-by-station measurements reveals that K, U, and Th concentrations show an elevation trend at Robinson Mountain and generally higher concentrations near Sugarloaf Peak’s summit, suggesting progressive magmatic differentiation and/or the presence of more evolved lithologies at higher elevations. By mapping these elements on Earth using GRNS, we aim to optimize measurement techniques for Lunar-VISE and similar rover-borne missions by demonstrating the applicability of portable GRNS instruments for planetary surface exploration in an analog environment.

Arizona↗

USGS2025

Characterizing Meteor Crater impact melts through geochemistry and textural analysis

The U.S. Geological Survey Astrogeology Science Center houses the Meteor Crater sample collection, an assemblage of over 2,500 meters of cuttings from 161 drill holes into Meteor Crater’s rim, flanks, and ejecta blanket. We have utilized this unique collection to study the composition and spatial distribution of impact-generated materials from within the ejecta blanket. Meteor Crater has historically been known to have generated only a relatively small amount of impact melt compared to other terrestrial craters of similar size. A detailed compositional and textural dataset of impact-derived melts from this impact can therefore be a useful asset in improving our understanding of crater formation, and in particular impact melt formation. We have characterized 42 impact-melt particles from Meteor Crater using a scanning electron microscope and an electron microprobe for textural and compositional analysis. We analyzed samples from six drill holes in the ejecta blanket, situated to the northwest, southeast, south, and southwest of the crater (ejecta northeast of the crater is devoid of impact melts). Impact melts were collected from drill cuttings at various depths within the ejecta blanket, ranging from a few centimeters below the surface down to ~6.5 meters. Backscattered electron (BSE) images were acquired for each analyzed impact-melt particle. To characterize the various textures and phases present in each impact melt, we also took many detailed BSE images. Our geochemical analyses include full spectral profiles using energy dispersive X-ray spectrometry and well-calibrated wavelength dispersive spectrometry for a number of phases, including minerals (olivine, pyroxene, and so on), pristine glass, and metallic inclusions. The full dataset is available in ScienceBase as a data release (Gullikson and others, 2024), accessible at https://doi.org/10.5066/P9OGAJ8P . Our goal for this Open-File Report is to provide a summary of this immense dataset, details on data collection, descriptions of the different phases observed within impact-melt particles (both geochemically and texturally), and observable trends.

Arizona↗

USGS2024

Assessing community needs for terrestrial analog studies

Executive Summary The U.S. Geological Survey (USGS) developed and released a survey to assess the terrestrial analog needs of the planetary science community. The goal was to assess the current state of terrestrial analog studies and determine community needs related to the use of field sites for training and research, data dissemination and archiving, and sample collections. The survey was designed to gather feedback from community members who have a self-described interest in the use of terrestrial analogs. The web-based questionnaire contained a total of 33 questions and was designed to take <10 minutes to complete. The questionnaire was divided into four sections: (1) “Respondent Details,” (2) “Field Analog Use,” (3) “Data Portal Use,” and (4) “Geologic Materials Collection Use.” Comment boxes were provided for 12 of the 33 questions, which allowed respondents to provide more detailed comments to individual questions. The questionnaire received a total of 248 responses. We identified 21 notable findings which are matched with one or more recommendations to be addressed by the planetary science community. In general, the findings highlight the importance of terrestrial analog studies to the planetary science community. The findings address how and why the community uses terrestrial analogs, areas in which further support can lead to a greater return on investment, and how the community can better manage data and samples from these studies. The results from this survey identify a need for additional training opportunities and analog-focused workshops. There is a gap in formal education related to field techniques for a significant part of researchers who conduct fieldwork. There is also a subset of the community who are interested in conducting field-based studies but are, however, unaware of relevant sites and methods. Workshops would provide an opportunity for scientists at all career stages to share their results and discuss common challenges such as logistics, field safety, funding, and data and sample archiving. Trainings, workshops, and better communication may also lead to increased field-analog work at locations in closer proximity to home institutions, reducing costs associated with large field expeditions and ultimately leading to more available funding for more localized field studies. The survey also shows that the ability to archive a diverse array of field data is a major challenge for terrestrial studies and finds that existing practices are not compliant with National Aeronautics and Space Administration (NASA) data management policies. The survey points to a strong need for a central data repository, allowing for easier access to existing analog data and the archiving of new field data. The community would benefit from additional physical sample archiving, consolidated into several key institutions to promote easier access, such as NASA and USGS centers. Though scientists would still need to acquire their own samples in the field for certain studies, many studies would benefit from an archive of existing samples and associated data for widely used analog sites, reducing redundant sampling practices. This report finds that a coordinated effort to improve and standardize training, data archiving, sample curation, and communication regarding terrestrial analog studies will best serve the planetary science community in our exploration goals.

Open-File Report↗

USGS2024

U.S. Geological Survey Karst Interest Group proceedings, Nashville, Tennessee, October 22-24, 2024

Karst hydrogeologic systems represent challenging and unique conditions to scientists studying groundwater flow and contaminant transport. Karst terrains are characterized by distinct and beautiful landscapes, caverns, and springs, and many of the exceptional karst areas are designated as national or state parks. The range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than any other aquifer type. The U.S. Geological Survey (USGS) Karst Interest Group (KIG), formed in 2000, is a loosely knit, grassroots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst aquifers. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. To accomplish its mission, the KIG has organized a series of workshops. To date (2024), nine KIG workshops, including the workshop documented in this report, have been held. The abstracts and extended abstracts provide a snapshot in time of past and current karst related studies. The USGS Water Availability and Use Science Program funded the workshop and proceedings. The planning committee for the ninth workshop includes Thomas D. Byl (USGS and Tennessee State University), Allan K. Clark (USGS), Laura M. DeMott (USGS), Eve L. Kuniansky (USGS, Emeritus), Benjamin V. Miller (USGS), and Lawrence E. Spangler (USGS, Emeritus). The workshop proceedings are edited by Eve L. Kuniansky and Lawrence E. Spangler. The field trip guide was produced by Benjamin V. Miller and Brian Ham (Tennessee Department of Environment and Conservation) and included in the proceedings from the KIG’s 2021 virtual workshop to be used on the optional field trip held on Thursday, October 24, 2024.

Open-File Report↗

USGS2024

A novel surface energy balance method for thermal inertia studies of terrestrial analogs

Surface thermal inertia derived from satellite imagery offers a valuable tool for remotely mapping the physical structure and water content of planetary regolith. Efforts to quantify thermal inertia using surface temperatures on Earth, however, have consistently yielded large uncertainties and suffered from a lack of reproducibility. Unlike dry or airless bodies, Earth's abundant water and dense atmosphere lead to dynamic thermophysical conditions that are a greater challenge to model than on a world like Mars. In this work, an approach was developed using field experiments to inform and fine-tune a thermophysical model of terrestrial sediment and calculate an inherent thermal inertia value with higher precision and less initial knowledge of the sediment than has previously been achieved remotely on Earth. A thermal inertia derived for a basaltic tephra site in Northern Arizona was replicated within 1% between different field seasons, demonstrating reproducibility. Model-derived values were validated in situ by two different thermophysical field probes to within 8% of the measured mean values. Analog studies such as this hold the promise of improved interpretations of surface materials on Mars, and an accurate thermal model for Earth is the key step to enabling translation between the two worlds.

Earth and Space Science↗

USGS2024

Global survey of paleo-bedforms on Mars

Sedimentary processes on Mars have contributed to a plethora of landforms, both ancient and modern. Many of these are aeolian- or fluvial-formed constructs that meet the morphologic criteria for dunes and ripples but are clearly lithified and part of the rock record. This study conducted a survey of Mars using data returned from the High Resolution Imaging Science Experiment (HiRISE) to characterize the spatial distribution, origin, and geologic context of these preserved ancient bedforms, termed here as paleo-bedforms. The most compelling class include organized groups of 2–80-m-tall, crescentic to transverse features spaced at 100–1000 m wavelengths at Apollinaris Sulci, Valles Marineris, and other low-latitude sites. These morphologies along with superposed craters, boulders, and fractures led to the interpretation that these are highly lithified, friable, and partially eroded ancient aeolian dunes. In addition to lithified dunes, other remnants of ancient bedforms include examples in which the dune was completely removed, leaving a shallow depression in a crescentic outline as dune cast pits. The most widespread occurrences of paleo-bedforms show crest-to-crest wavelengths (10–80 m), heights (∼1–4 m), and morphologies consistent with lower-order bedforms of megaripples or transverse aeolian ridges. Paleo-megaripple fields in Arcadia Planitia, Hellas Planitia, Terra Sirenum, and other locations exhibit a progression of degraded morphologies, with crests showing signs of rounding, pitting, or fracturing, while heights and slopes are diminished due to erosion. Most rare are the paleo-bedforms in the fluvial bedform class at Lethe Vallis and Holden crater, as they occur along the path of proposed ancient flooding events. More enigmatic paleo-bedform candidates occur concentrated along the steep Valles Marineris and Noctis Labyrinthus wall slopes. These intermediate-sized, arcuate landforms that resemble transverse climbing dunes are heavily cratered, but they may align perpendicular or oblique to the local gradient, perhaps formed by wall slope winds and slope creep. The bedforms are unlike most ancient terrestrial aeolian or fluvial bedform systems, which are typically preserved only as truncated members of stratigraphic sections. Episodes of burial and exhumation by various geologic units (e.g., the Medusae Fossae Formation, pyroclastic units, lava flows, dust) are notable, whereas other bedforms appear to have been stabilized and partially lithified in place without burial. Ongoing agents of mass wasting, aeolian abrasion, and cryo-driven processes have contributed to the exhumation, erosion, and weathered appearance of paleo-bedforms, and a spectrum of degradation states was observed. Collectively, we report a diverse variety of ancient sedimentary bedforms preserved across Mars, with implications about paleoclimates and landscape evolution on Mars.

Geomorphology↗

USGS2023

Morphology and paleohydrology of intracrater alluvial fans north of Hellas Basin, Mars

Alluvial fans and sinuous ridges are both important records of the history of fluvial activity on Mars, and they often occur together. We present observations of alluvial fans, many of which exhibit inverted relief, in five craters in the region north of Hellas basin. The observed fans ranged in size from ~10 to 820 km 2 . We identified three primary fan surface morphology classes (chute, degraded, and Inverted) as well as many instances where the morphology transitions from proximal chutes (or, rarely, a cratered degraded surface) to distal ridges corresponding to increasing thermal inertia. Clear superposition relationships at contacts between adjacent fans are rarely observed, suggesting interfingered deposits and concurrent fan development across the region. Localized factors appear to influence fan development as there is no systematic trend in the azimuth range of fan location, size of fan or catchment, as well as the degree of crater filling. Water and sediment availability may be controlled by lithology differences and weather patterns. Many of the fans had a mismatch between catchment and fan volume, corresponding to significant amounts of erosion perhaps due to windblown stripping of fine sediment. However, several notable fans exhibited volumes greater than their corresponding catchments. This may reflect uncertainty in the accuracy of the estimated paleosurface, or it may indicate sediment contributions to the fan from outside the mapped catchment. Ridges, inferred to be the resistant remnants of fluvially transported deposits, were used to estimate flow magnitude in fan construction with computed discharges of 60–400 m 3 /s and corresponding supply rate runoff values ~1–20 mm/h. Acknowledging that width-derived discharge values may overestimate flow conditions due to the likelihood of amalgamated channel deposits, this quantification provides important climate constraints. The upper range of runoff values and discharge rates are quite high, and would require either intense rain storms to generate immediate runoff, or longer-term snow accumulation and subsequent melt-runoff, potentially enhanced by rain-on-snow events. Minimum continuous formation time scales of less than a century are computed, but are incompatible with fan morphology (e.g., superposition relationships, embedded craters) and mechanisms to sustain flows. More realistic lower-limit fan construction times, accounting for modeled precipitation rates from the literature, are tens to hundreds of thousands of years. Fans were active in multiple events spanning the Hesperian to Amazonian periods, requiring transient climate conditions to support the fan aggradation.

Icarus↗

USGS2023

Spatial and temporal distribution of sinuous ridges in southeastern Terra Sabaea and the northern region of Hellas Planitia, Mars

Sinuous ridges are an important yet understudied component of Mars' hydrologic history. We have produced a map of sinuous ridges, valleys and channels, and tectonic ridges across southeastern Terra Sabaea and into northern Hellas Planitia (10°-45° S, 35°-80° E) using a CTX mosaic. Although we mapped different types of ridges and negative relief features, the focus of this paper are the sinuous ridges. We present here a new dataset of sinuous ridges that includes basic morphometry (e.g., length, width, sinuosity), morphology, and the types of terrains they are located on. We chose our region of interest because it includes surface ages spanning Mars' geologic history, with emphasis on Noachian and Hesperian terrains. The shift from either a warm and wet or a cold and icy environment to our modern cold and dry climate occurred towards the end of the Noachian and into the Hesperian, a critical temporal window to characterize fluvial landforms. Our CTX-based mapping significantly improved the documentation of fluvial landforms within the study region, with over an order of magnitude increase in the number of valley networks and channels, and nearly 1700 sinuous ridges. Sinuous ridges are found in concentrated settings, with the majority (∼80%) located within impact craters and relatively few (∼20%) on the intercrater plains. Fluvial features are prevalent on Early and Middle Noachian-aged terrain but are relatively rare in the Late Noachian, signifying a shift in fluvial activity that likely led to a decrease in channel incision and subsequent inversion of relief. A subset of sinuous ridges—radial ridges in high-elevation, degraded craters— are possible records of ancient proglacial lakes. The youngest sinuous ridges are associated with intracrater alluvial fans in a narrow zone (∼12°S to 30°S and ∼ 62°E to 77°E). These formed in the Late Hesperian into the Amazonian, reflecting a later epoch of punctuated fluvial events driven by pre-existing topography and solar insolation.

Icarus↗

USGS2022

Thermophysical and compositional properties of paleobedforms on Mars

Bedforms on Earth and Mars are often preserved in the rock record in the form of sedimentary rock with distinct cross-bedding. On rare occasions, the full-surface geometry of a bedform can be preserved through burial and lithification. These features, known as paleobedforms, are found in a variety of geographic locations on Mars. Evidence in the morphology of paleobedforms, such as the retention of impact craters and steep erosional scarps, suggests that these features are well-lithified and capable of withstanding prolonged weathering and erosion. Here, we present results from thermophysical and compositional analyses on a subset of the best preserved paleobedform candidate fields on Mars. Thermophysical modeling elucidates the changes these bedforms underwent from their unconsolidated, particulate nature to their currently observed properties. Certain paleobedforms have elevated thermal inertias (e.g., ∼300–500 J·m −2 ·s −1/2 ·K −1 ) when compared with modern bedforms (∼250 J·m −2 ·s −1/2 ·K −1 ), and modeling indicates that they have cement volumes of 0.8%–1.5% even as high as 30%. However, most paleobedform candidates have unexpectedly low thermal inertia when compared with modern dunes. Additionally, compositional analyses reveal a range of spectral characteristics within paleobedforms (e.g., primary and secondary alteration products). These features add to the already existing class of Martian surfaces in which thermal inertia does not seem to correspond to erodibility, cohesion, or mechanical strength. Studying paleobedforms with both raised and nonraised thermal inertia has provided new insights into lithification on Mars and constrained the environmental conditions leading to the formation of these enigmatic features.

Journal of Geophysical Research - Planets↗

USGS2021

A geologic field guide to S P Mountain and its lava flow, San Francisco Volcanic Field, Arizona

Introduction We created this guide to introduce the user to the San Francisco Volcanic Field as a terrestrial analog site for planetary volcanic processes. For decades, the San Francisco Volcanic Field has been used to teach scientists to recognize the products of common types of volcanic eruptions and associated volcanic features. The volcanic processes and products observed in this volcanic field are like those observed on lunar and Martian surfaces. As a result, this region has been a favored location for training National Aeronautics and Space Administration astronauts and engineers since the Apollo missions. Though the San Francisco Volcanic Field has more than 600 volcanic vents and flows, this guide will focus on S P Mountain (known locally as S P Crater, located ~30 miles north of Flagstaff, Arizona), one of the best preserved and most accessible of the volcanic cones and lava flows. S P Mountain presents both major types of basaltic eruptions—explosive and effusive—as well as some commonly associated tectonic landforms. We assume that the user has a basic understanding of geologic concepts and terminology. For more specialized terminology, we include tables showing the classification scheme for lava compositions, styles of eruptions, and tephra sizes (tables 1, 2, and 3). If a further introduction or refresher in volcanological terminology is desired, we suggest reviewing such terms on the U.S. Geological Survey Volcano Science Center’s online glossary ( https://volcanoes.usgs.gov/vsc/glossary/ ). One term requires clarification at the start of this guide—the term cinder. The terms cinder and cinder cone are widely used to describe the material and edifice produced by lava fountains. However, the term comes from the mining and construction industries and has no clear or formal definition. The international committees in geology and volcanology have chosen the term tephra to be the general term to describe pyroclasts (material ejected through a volcanic explosion or from a volcanic vent). Therefore, in this guide, we use the term tephra rather than cinder. This guide is outlined as follows: A brief tour of volcanism across the solar system A brief geologic history of the Colorado Plateau and San Francisco Volcanic Field Background on distributed volcanism and S P Mountain Driving directions and field stops Questions for discussion Each field stop includes a brief description, learning goals, tasks, and a summary of key points. At the end of the field guide are discussion points and questions that will ask the user to consider what they have observed and learned and how such knowledge can be used to better our understanding of geologic processes on other planetary bodies. Upon the completion of this field guide, we expect the user to: Have a basic understanding of the volcanic processes relevant to S P Mountain and its lava flow. Be able to identify different volcanic textures that are associated with tephra cones. Be aware of the different observations one can make at different scales (for example, observing lava flow morphology from aerial or satellite imagery versus tephra characteristics in the field).

Arizona↗

USGS2021

Workshop on terrestrial analogs for planetary exploration

Terrestrial analogs are an important part of the robotic and human exploration of the solar system. One of the main recommendations from a community survey conducted in 2019 was to hold a workshop to increase communication and share resources among scientists, engineers, data managers, educators, and students who are involved, or hope to be involved, in terrestrial analog studies.

Lunar and Planetary Information Bulletin↗

USGS2020

The Mars Global Digital Dune Database (MGD3): Composition and stability

We present an expansion to the Mars Global Digital Dune Database (MGD3) describing 1) bulk dune field composition determined by fitting a mineral spectral library to Thermal Emission Spectra (TES) data, and 2) a morphologic stability index that measures the degree of non-aeolian modification that has eroded and stabilized each dune field. This paper describes results for these two components, providing insight into global patterns of dune sand sources, postdepositional alteration, and mineral maturity. Consistent with the work of others, the main mineral components of each analyzed dune field are feldspar, pyroxene, and high-silica phases, with minor amounts of olivine and possibly sulfate minerals. Subtle global-scale spatial variations in olivine and feldspar abundances correspond with previously observed trends in surface mineralogy, suggesting that dune sand is reflective of its regional setting, and thus that aeolian sand has typically not traveled far (<~100s of km) from its source regions. Dune-field-scale stabilization features are found mainly south of 60S, and in a few areas north of 60N, consistent with observed dune and ripple migration rates in these areas. The presence of such stabilization features may be an indicator of where bedform migration rates are low. Abundances of high-silica phases are elevated in some dune fields located in the southern mid- to high-latitudes, particularly in those dune fields located on intercrater plains, where stabilization features tend to be less well developed and where ripples tend to be actively migrating. This correlation of high-silica phase abundance with bedform activity also occurs in the north polar sand seas. In the north polar sand seas, this spectral signature has been attributed to iron-bearing glass that has been weathered through acid leaching, leaving behind silica-enriched rinds, and kept free of any precipitated coatings through active saltation. We hypothesize that near and thermal infrared spectral signatures of acid leaching are indicators of aeolian activity, and thus potentially of mineral maturity, in dune sands abundant in iron-bearing glass.

Icarus↗

USGS2018

Mars global digital dune database (MGD3)—Composition, stability, and thermal inertia

The Mars Global Digital Dune Database (MGD 3 ) is an online repository that has catalogued dune fields larger than 1 km 2 located between latitudes 90° N. and 90° S. The work presented here expands upon previous MGD3 open-file reports, with a new emphasis upon characterizing dune fields through composition, stability, and thermal inertia. Included in this latest addition is a detailed compositional analysis and the associated observational data from Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) for dune fields 300 km 2 or larger; a near-global dune stability assessment; Mars Odyssey (MO1) Thermal Emission Imaging System (THEMIS) apparent thermal inertia values; and vertical near-surface thermophysical heterogeneities determined by fitting a two-layer thermal model to observed temperatures. These additional datasets are divided into two workbooks: equatorial and south polar regions. A detailed description for the layout of these workbooks can be found in the corresponding metadata document. The continuing goal of the MGD 3 is to provide a reliable and multifaceted repository of data for Mars’ dunes, with the intention that such data be easily accessible and useful to future research.

Open-File Report↗