Martian secondary craters imply the existence of liquid water: High
velocity impact experiments onto wet sand
Abstract
Gratteri crater is a young Martian crater which still retains secondary
craters, and some of them have unique ejecta deposits similar to
mudflows splattered by impacts, suggesting that they might have been
formed on wet sand-like material. Interestingly, the morphologies of
Gratteri secondary craters vary among regions. We conducted crater
formation experiments onto wet sand targets with different water
contents and observed that the crater size and morphology changed with
target water content. We established a crater size scaling law for wet
sand which can account for water content change. Our scaling law
suggests that the region 103 km away from the Gratteri crater might have
had a higher water content than the region 32 km away (≥4.6 wt.% vs.
<2.0 wt.%, respectively), judging from the sizes and
morphologies of its secondary craters in each region.