MAPPING LAVA FLOW FIELDS IN THE THARSIS REGION OF MARS: INSIGHTS FROM TERRESTRIAL ANALOGUE STUDIES FOR CHARACTERIZING PĀHOEHOE FLOW SIGNATURES

We are conducting detailed mapping investigations of lava flow fields on Mars to characterize the distribution, types, topographic attributes, and volcanic settings for pāhoehoe-like flow morphologies that can now be documented in high-resolution datasets. Here we examine select parts of the expansive flow fields surrounding shield volcanoes in the Tharsis Volcanic Province and a series of pāhoehoe flow features from terrestrial basaltic flow fields that serve as analogues for interpreting Martian landforms. Our southern Tharsis study region (10-40°S, 115-145°W) includes lava flow fields that comprise the SW rift apron of Arsia Mons, form Daedalia Planum, and extend to form the southern distal reaches of Tharsis. Our eastern Tharsis study region (0-15°N, 85-107°W) consists of volcanic plains east of Ascraeus and Pavonis Montes where rift apron flows are mixed with flows sourced at small local vents toward Tharsis’ eastern margin. Both locations exhibit complex flow field surfaces where different lava flow types show local overlapping relationships and downslope progressions analogous to terrestrial basaltic flow fields that consist of ‘a‘ā and pāhoehoe. Initial mapping has focused on a) vents, b) distributary features for pāhoehoe-like lavas, c) central channels of ‘a‘ā-like flows, and d) flow inflation features (as common in terrestrial pāhoehoe). Pāhoehoe distributary pathways are defined by one or more features, including narrow channels, perched channels, lava tubes (often as ridges with lateral flow texture), sinuous ridges/plateaus, and various secondary vents. Inflated lava flows are distinguished by flat, smooth surfaces and steep, irregular margins, sometimes with associated digitate lobes at their bases. Inflation plateaus are common in both Tharsis study regions, occurring as lateral or downslope extensions of pāhoehoe distributary features, as well as along the margins of broad lobes and sheet flows that dominate medial and distal flow field zones in southern Tharsis. We are utilizing images and DEMs of terrestrial basalt flows, including from low altitude drone surveys, to characterize pāhoehoe flow surface features/textures and flow margin characteristics, including those related to flow inflation, to inform interpretations of pāhoehoe-like flow morphologies on Mars and examine the role of pāhoehoe in Martian flow field evolution.