Stephen Paul Scheidt

Hesperian age for western Medusae Fossae Formation, Mars.

Counts of impact craters provide age for a region on Mars close to the landing site of rover Curiosity. The Medusae Fossae Formation (MFF) on Mars is an intensely eroded deposit north of the cratered highlands. It is widely thought that MFF materials were emplaced through ignimbrite eruptions. Recent geologic mapping of western MFF identified outliers of MFF materials well beyond the previously mapped western extent for the deposit, including outliers close to Gale crater. We report counts of impact craters on the MFF units that have implications for our understanding of the general history of MFF and the uppermost layered materials on the Gale crater mound.

Determining soil moisture and sediment availability at White Sands Dune Field, New Mexico, from apparent thermal inertia data

[1] Determinations of soil moisture and sediment availability in arid regions are important indicators of local climate variability and the potential for future dust storm events. Data from the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer were used to derive the relationships among potential soil erosion, soil moisture, and thermal inertia (TI) at the spatial scale of aeolian landforms for the White Sands Dune Field between May 2000 and March 2008. Land surface apparent thermal inertia (ATI) data were used to derive an approximation of actual TI in order to estimate the wind threshold velocity ratio (WTR). The WTR is a ratio of the wind velocity thresholds at which soil erosion occurs for wet soil versus dry soil. The ASTER‐derived soil moisture retrievals and the changes through time at White Sands were interpreted to be driven primarily by precipitation, but the presence of a perched groundwater table may also influence certain areas. The sediment availability of dunes, active playa surfaces and the margin of the alluvial fans to the west were determined to be consistently higher than the surrounding area. The sediment availability can be primarily explained by precipitation events and the number of dry days prior to the data acquisition. Other factors such as vegetation and the amount of surface crusting may also influence soil mobility, but these were not measured in the field. This approach showed the highest modeled sediment availability values just days prior to the largest dust emission event at White Sands in decades. Such an approach could be extended to a global monitoring technique for arid land systems that are prone to dust storms and for other regional land surface studies in the Sahara.

Eolian dynamics and sediment mixing in the Gran Desierto, Mexico, determined from thermal infrared spectroscopy and remote-sensing data

The Gran Desierto dune field is only partially composed of quartz-rich sands from the ancestral Colorado River. Local sources have been previously underestimated as a major source of sand because previous remote-sensing studies were limited in their capability to detect silicate minerals. Compositions of sands were evaluated in this study using a combination of laboratory thermal emission spectroscopy and thermal remote-sensing data acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. The spatial interpolation of sample compositions allowed visualization of the sand transport pathways from feldspar-rich local sources by revealing gradients of composition between the dune field and surrounding local sources. The laboratory data were comparable to the remote-sensing retrievals of quartz and feldspar abundance. The mineralogical maturity of the Desierto dunes could be determined by the quartz/feldspar ratio, therefore providing a context for understanding the provenance of the Gran Desierto in relation to other Mojave and Sonoran dune fields. The composition of a previously undescribed group of dunes east of the Pinacate, the Sonoyta dunes, was measured as higher in potassium feldspar relative to the rest of the dune field. The composition of Sonoyta dunes is characteristic of other Mojave dune fields, which are more isolated near local feldspar-rich sources. South of the Pinacate, quartz-rich sand from the west admixes with feldspar-rich sand from the Sonoyta dunes to the east. The northern margin of the Gran Desierto is similarly enriched in feldspar from alluvial fans, and the coastal sand is influenced by carbonate sand that does not appear to survive transport to the inland dunes.

Automated detection of geological landforms on Mars using Convolutional Neural Networks

The large volume of high-resolution images acquired by the Mars Reconnaissance Orbiter has opened a new frontier for developing automated approaches to detecting landforms on the surface of Mars. However, most landform classifiers focus on crater detection, which represents only one of many geological landforms of scientific interest. In this work, we use Convolutional Neural Networks (ConvNets) to detect both volcanic rootless cones and transverse aeolian ridges. Our system, named MarsNet, consists of five networks, each of which is trained to detect landforms of different sizes. We compare our detection algorithm with a widely used method for image recognition, Support Vector Machines (SVMs) using Histogram of Oriented Gradients (HOG) features. We show that ConvNets can detect a wide range of landforms and has better accuracy and recall in testing data than traditional classifiers based on SVMs.

Episodes of Aqueous Flooding and Effusive Volcanism Associated With Hrad Vallis, Mars

NASA Planetary Geology and Geophysics Program NASA Planetary Science Division [NNX13AR14G, 80NSSC17K0307]; NASA Earth and Space Sciences Fellowship (NESSF) Program [NNX16AP09H]