Degradation of Homestead Hollow at the Insight Landing Site Based on the Distribution and Properties of Local Deposits

Abstract

The InSight mission landed its scientific payload in Homestead hollow, a quasi-circular depression interpreted to be a highly degraded impact crater that is 27 m in diameter. The original pristine crater formed in a pre-existing impact-generated regolith averaging 3 m thick and the surrounding ejecta deposit, consisting of coarse and mostly fine fragments, was in disequilibrium with local geomorphic thresholds. As a result, early, relatively rapid degradation by mostly eolian, and lesser impact processes and mass-wasting, stripped the rim and mostly infilled the hollow where sediments were sequestered. Early, faster degradation during the first 0.1 Ga was followed by much slower degradation over the bulk of the 0.4-0.7 Ga history of the crater. Pulses of much lesser degradation are attributed to impacts in and nearby the hollow, which emplaced some rocks as ejecta and provided small inventories of fine sediments for limited additional infilling. Even lesser sediments were derived from the very slow production of fines via weathering of resistant basaltic rocks. Nevertheless, indurated regolith caps the sediment fill within the hollow and creates a relatively stable present-day surface that further sequesters infilling sediments from remobilization. The degradation sequence at Homestead hollow is like that established at the Spirit rover landing site in Gusev crater and points to the importance of eolian, and lesser impact and mass-wasting processes, in degrading volcanic surfaces on Mars over the past 1 Ga.