T246 The InSight Mission to Mars: Geology of the Landing Site

Wednesday, 25 September 2019
8:00 AM - 12:00 PM
Room 232BC, North Building

SURFACE ALTERATION FROM LANDING INSIGHT ON MARS AND ITS IMPLICATIONS FOR SHALLOW REGOLITH STRUCTURE

Paper number: T246-9
Program: Technical Sessions
Time: 10:05 AM – 10:20 AM

Authors

Abstract

The Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) mission used retropropulsive pulse thruster rockets to slow the lander’s descent and perform a safe soft landing at Homestead hollow in Elysium Planitia on Mars. Rocket exhaust from landings on Mars and Earth’s Moon modify the near surface by redistributing primarily fine-grained materials. This surface alteration is most easily identified as “halos” of albedo, color, and/or textural variations in visible images. We use orbiter and lander images to characterize surface alteration caused by InSight landing and compare to previous landing sites and impacts to assess the surface properties and very near surface structure of the regolith.

High Resolution Imaging Science Experiment (HiRISE) orbital images reveal an inner halo extending up to 8-11 m from the lander with an 18% lower relative albedo compared to unaltered background. It is surrounded by a darker outer halo extending from the edge of the inner halo out to 15-21 m (~990 m2 area) from the lander with up to a 35% lower relative albedo compared to unaltered background. The outer halo also extends more weakly much farther to the southeast along the expected prevailing wind direction. Images taken by InSight also show a slight darkening of the mid-field surface up to 20 m away relative to the far-field, approximately coincident with the edge of Homestead hollow. The disturbed zone around InSight is remarkably similar to that of the Phoenix Mars lander (same lander system) of 18 m mean radius (1020 m2).

Darkening of the surface around InSight is consistent with the expected removal of a thin layer (microns) of dust during landing similar to previous Mars landing sites, fresh impacts, and analogous to the formation of typical dust devil tracks. Images taken by InSight also show radial linear grooves and ridges several mm in relief and many pebbles with tails extending away from the lander suggesting scour from landing. This indicates that landing likely removed <1 cm of proximal unconsolidated surface material, exposing shallowly buried material underneath. The rockets also excavated steep-sided pits under the lander that suggest a mildly cohesive duricrust. This duricrust is relatively light-toned, and its partial exposure may produce the bright inner halo observed in orbital images.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-340531

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