In Situ and Orbital Stratigraphic Characterization of the InSight Landing Site-A Type Example of a Regolith-Covered Lava Plain on Mars

The InSight lander rests on a regolith-covered, Hesperian to Early Amazonian lava plain in Elysium Planitia within a similar to 27-m-diameter, degraded impact crater called Homestead hollow. The km to cm-scale stratigraphy beneath the lander is relevant to the mission's geophysical investigations. Geologic mapping and crater statistics indicate that similar to 170 m of mostly Hesperian to Early Amazonian basaltic lavas are underlain by Noachian to Early Hesperian (similar to 3.6 Ga) materials of possible sedimentary origin. Up to similar to 140 m of this volcanic resurfacing occurred in the Early Amazonian at 1.7 Ga, accounting for removal of craters <= 700 m in diameter. Seismic data however, suggest a clastic horizon that interrupts the volcanic sequence between depths of similar to 30 and similar to 75 m. Meter-scale stratigraphy beneath the lander is constrained by local and regional regolith thickness estimates that indicate up to 10-30 m of coarse-grained, brecciated regolith that fines upwards to a similar to 3 m thick loosely-consolidated, sand-dominated unit. The maximum depth of Homestead hollow, at similar to 3 m, indicates that the crater is entirely embedded in regolith. The hollow is filled by sand-size eolian sediments, with contributions from sand to cobble-size slope debris, and sand to cobble-size ejecta. Lander-based observations indicate that the fill at Homestead hollow contains a cohesive layer down to similar to 10-20 cm depth that is visible in lander rocket-excavated pits and the HP3 mole hole. The surface of the landing site is capped by a similar to 1 to 2 cm-thick loosely granular, sand-sized layer with a microns-thick surficial dust horizon.