AEOLIAN CHANGE DETECTION FROM THE INSIGHT LANDER

Repeat “change detection” imaging has been successfully utilized by numerous orbiting and landed spacecraft to monitor active aeolian (wind-driven) transport occurring on Mars. The Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission provides a rare opportunity to acquire change detection images in conjunction with continuous, high-frequency wind measurements. These experiments can help shed light on past and present aeolian activity at the InSight landing site, and on Martian aeolian transport as a whole, particularly with respect to fluid threshold speeds. Systematic images were acquired with the Instrument Context Camera (ICC) and less frequently with the Instrument Deployment Camera (IDC), and atmospheric data (i.e., wind speed and pressure) were provided by the Auxiliary Payload Sensor Suite (APSS). The results of change detection experiments thus far have suggested that the surface around the lander is generally stable (at least at the resolution of the lander’s cameras), with only four localized changes observed over the first 200 sols of the mission. Low levels of wind-driven surface activity are consistent with the paucity of active aeolian bedforms seen from orbit. Three of the observed changes occurred within a pile of sediment that accumulated on the west footpad after landing, which was selected as one of the primary change detection targets due to the lack of aeolian bedforms in the lander’s view. Each of the footpad changes involved apparent removal of fines, and the fourth change was noticeable by a localized surface color change within the workspace; all four changes coincided with a significant drops in atmospheric pressure detected by APSS (indicative of passing convective vortices), including the largest pressure drop yet detected on Mars (9 Pa on Sol 65). The peak winds associated with these vortex events are very likely not capable of generating saltation, as the fluid threshold for even the most susceptible grain sizes has only been exceeded once during the mission thus far (28 m/s on Sol 26). This discrepancy may be reconciled by considering that: 1) fluid threshold equations were developed for organized aeolian bedforms, which are not representative of the footpad pile and/or 2) the pressure well effect within a convective vortex can cause mobilization at sub-threshold wind speeds.