Presentation #311.08 in the session “Mars Surface”.
Previous studies have suggested that most lava flows on Mars are basaltic, pāhoehoe flows with a “platy-ridged” texture (Jaeger et al., 2010; Keszthelyi et al., 2006; 2004; 2000); however, ground-based radar observations using the Arecibo Observatory S-band (12.5 cm, 2380 MHz) planetary radar revealed that the roughness properties of Martian lavas differ from terrestrial platy-ridged flows (Neish et al. 2017; Harmon et al. 2012). At the decimeter scale, Martian lavas are radar bright and have high circular polarization ratios, which are characteristic of extremely rough, andesitic, blocky lava flows on Earth. To resolve this discrepancy, we compared the decimeter-scale radar results with meter-scale roughness properties determined from MRO HiRISE images. We constructed digital terrain models of 35 lava flows to measure their meter-scale surface roughness parameters. Our results show that Martian lava flows are smoother than blocky flows seen on Earth at the meter-scale, and similar in roughness to terrestrial pāhoehoe and rubbly flows, as well as young lunar lava flows. Thus, while at the decimeter scale in radar these lava flows appear rough, they are smooth at the meter scale. The differences observed in the surface roughness of Martian lava flows compared to analogue lava flows on Earth and the Moon might be the result of: 1) the differences in the emplacement style of the lava flows, 2) the differences in post-emplacement modification processes on the surface of the lava flows, and/or 3) the limitations of the technique used to characterize the lava flows. Further data is thus needed to understand the unusual properties of Martian lava flows. We plan to use new radar imagery of Mars from future ground-based radar observations to help us understand the emplacement of lava flows on Mars.