Evidence for marine sedimentary rocks in Utopia Planitia: Zhurong rover observations

Abstract

Decades of research using remotely sensed data have extracted evidence for the presence of an ocean in the northern lowlands of Mars in the Hesperian (∼3.3 Ga), but these claims have remained controversial due to the lack of <i>in situ</i> analysis of the associated geologic unit, the Vastitas Borealis Formation (VBF). The Tianwen-1/Zhurong rover was targeted to land within the VBF near its southern margin and has traversed almost 2 km southward toward the interpreted shoreline. We report here on the first <i>in situ</i> analysis of the VBF that reveals sedimentary structures and features in surface rocks that suggest that the VBF was deposited in a marine environment, providing direct support for the existence of an ancient (Hesperian) ocean on Mars.