UAV SURVEYS OF INFLATED PAHOEHOE LAVA FLOWS: ANALYSES OF TERRESTRIAL ANALOGS FOR THE INTERPRETATION OF ORBITAL OBSERVATIONS OF MARS

This research examines inflated pahoehoe lava flows in New Mexico as terrestrial analogs to inform geological analyses of volcanic contact relationships on Mars. Our focus is on the floor of Gusev crater, with numerous localities which have preserved volcanic units in contact with the pre-existing terrain. Field characterization of lava flows with different degrees and styles of flow inflation is complicated by the scale of lava flow fields, accessibility, and topography. Orbital remote sensing provides important perspectives but is challenging due to vegetation cover, data coverage/spatial resolution, and similar characteristics of adjacent lava flow surfaces. These problems are addressed using data from low-altitude uncrewed aerial vehicle (UAV) surveys at high priority sites along flow margins. We produced orthomosaics (≤ 5 cm/pixel) and digital terrain models (DTMs, 10 cm/pixel) that show the surface detail needed to assess large-scale flow morphology, fine-scale textures, and relationships with topographic obstacles. To-date, UAV surveys at the Aden and at Carrizozo flow fields have been completed. Both flow fields exhibit a series of morphologies due to flow inflation, from small-scale inflation of digitate networks with toes, sheets, and small ropy-surfaced channels to more significant and larger-scales affecting multiple emplacement units forming tumuli, lava-rise pits, and pressure ridges/plateaus. Results are presented from a combination of pixel-based supervised classifications and accuracy assessments of image data and morphometric analyses from DTMs. In combination with airborne LiDAR, these data allow systematic, detailed morphologic, topographic, and textural characterizations of flow surfaces and margins. Thus, we can document the effects and magnitudes of flow inflation, and facilitate informed interpretations of contact relationships. Fracture patterns due to cooling of flow surfaces (i.e., polygonal) and large-scale inflation (margin parallel inflation clefts) can be identified. Accumulations of fine-grained sediments accentuate fracture patterns and also provide constraints on the degree of aeolian deposition. From image classification, we are able to distinguish lava surfaces and textures that are in agreement with lava flow observations in the field.