Identification of Sinuous Ridges in Solis Planum on Mars: Possibly Lave-tube Origin

Sinuous Ridge (SR) is a curvilinear feature with positive relief, which is also referred to as "raised curvilinear feature" (RCF). More than 1,000 SRs have been identified on martian surface and most of them are considered as inverted stream valleys or eskers in origin. Our study region, Solis Planum, is a large lava plain located in the southeast of the Tharsis region and formed mainly in Hesperian. We identified 47 SRs in Solis Planum for the first time and analyzed their morphology, thermophysical properties and relative ages in detail using CTX, HiRISE, HRSC and THEMIS data. Our results show that the SRs have multiple cross-section types and different thermophysical properties, and most SRs formed in late Hesperian. We also found some distinctive morphologic features associated with the SRs such as lineation, depressions and lobate features. Based on these observations, we proposed that the origin of these SRs is related to lava tubes, which is different from most of the SRs investigated in previous studies. Besides, SRs in Solis Planum could be feeding tunnels for the relatively young lavas on the plain far away from Tharsis Montes.