LAVA OR ICE? FIELD STUDIES OF TERRESTRIAL VOLCANIC ANALOGS FOR PLATY FLOWS ON MARS

Extensive regions of Mars are covered in enigmatic materials characterized by overall low relief and plate-like surface features. These materials appear to have flowed into place and their origins have been attributed to processes as varied as lava flows, mud/debris flows, and pack ice formation over a shallow sea. Since the platy deposits are observed within some of the most geologically youthful regions of Mars, such as Elysium Planum, and in near proximity to more typical volcanic and fluvial types of features, understanding the origins and associated mechanisms of these platy features is crucial in understanding the relatively recent geologic history of both Elysium Planum and Mars as a whole. This study uses data from the Mars Orbiter Laser Altimeter (MOLA), Mars Orbiter Camera (MOC), Thermal Emission Imaging System (THEMIS), and the High Resolution Stereo Camera (HRSC) for a quantitative approach to observation and analysis to gain a better understanding of these platy flows. The terrestrial field data is newly obtained from the Eastern Snake River Plains (ESRP), Idaho, an area commonly studied as an analog to martian plains volcanism. Several ESRP sites were chosen from orbital images for a variety of apparent plate-like morphologies, and visited to quantify flow measurements and apparent flow processes. We identify local features corresponding to the plates visible in the remote images, and measure plate and inter-plate diameters, perimeters, areas, topographic flow profiles, and intra-plate slopes using manual and differential GPS measurements, and sample each flow for geochemistry variations. While the appearance of the platy flow surfaces varies considerably in remote images, a readily apparent continuum of flow behavior is observable in the field data. Preliminary results suggest that ESRP volcanic flows form a variety of plate types at scales ranging from tens of cm to hundreds of meters (and more), and that ESRP plate formation mechanisms may include processes not previously recognized or well-described in the literature. We suggest that martian platy flows with morphologies previously described as atypical of volcanic flows—and thus attributed to ice formation and breakup—might be equally well explained as volcanic features.