GEOPHYSICAL INVESTIGATION OF THE INSIGHT LANDING SITE

InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) will conduct an investigation of Mars’ interior by placing a single geophysical lander on its surface. The principle science goal of InSight is to understand the formation and evolution of terrestrial planets through investigation of the interior structure and processes of Mars. Planetary heat flow measurement provides a constraint on radiogenic content and thermal evolution of a planet. Current constraints come from estimated elastic and thermal lithospheric thicknesses based on models of the loading of the lithosphere, which suggest both that there was a change in the heat flow during the early evolution of planet, and that the concentration of radiogenic elements may be lower than expected. In this work we sought to conduct a local fit to the crustal thickness using admittance modeling, as well as examine the possible origin of gravity anomalies in Elysium Planitia. Since local variations in density can affect the heat flow to a given region, we sought to refine the estimate of heat flow at Elysium Planitia as a function of crustal thickness and structure. We observe a high bouguer anomaly of ~400 mgal around InSight landing site indicating a higher density material in the subsurface. Admittance modeling is consistent with a high bottom to top loading ratio of 0.8. The crustal and lithospheric elastic thickness are between 10-50 km and 10-30 km respectively. To refine the constrain on elastic and crustal thickness we also evaluated the isostatic residual anomaly of the site and got an estimate for apparent depth of compensation (ADC) that is consistent with the estimate of low crustal thickness derived from the admittance modeling. A low top loading density is also observed at this location. Based on HiRISE images, isolated layers of friable material (most likely MFF deposit) possibly indicating presence of pyroclastic deposit is observe here. Continued work on this topic will help further refine the constraints on the crustal and elastic thickness, which will have significant implication in heat transfer modeling and interpretation once InSight lands.