Fig. 9. Interpretive cross section of the shallow subsurface beneath the InSight lander.
Most of the surficial bright, reddish dust (red, shown behind some rocks) has been dispersed around the lander (above 8). Rockier areas beyond ~20 m have more surface dust (6). The dust, which settled out of the atmosphere, is likely microns thick. About 1 cm of unconsolidated sand indicated by the radial surface striations and surface divots (9) underlies the dust. Observed in the pits beneath the lander (8) and in the mole hole is a duricrust of cemented sand, pebbles and rocks that is 5–10 cm thick (shown in blue), but could vary in thickness. Beneath the duricrust are overlapping craters (4, 5), rocks (7), and lens of ejecta from other craters (10). The relatively fine-grained impact generated regolith (3) is around 3 m thick beneath the lander and likely grades with depth into coarse, blocky ejecta (2) that overlies fractured basalt flows (1). Observations from the lander described in the text support the top 10 cm of the cross section. The bottom 13 m of the cross section are derived from estimates of the thickness of the relatively fine-grained regolith from rocky and non-rocky ejecta craters2,3,18 and the original depth of the Homestead hollow crater. Note the varying vertical scale.