Oceans in the past history of Mars: Tests for their presence using Mars Orbiter Laser Altimeter (MOLA) data

Abstract

An ancient north polar ocean on Mars has been proposed [ Parker et al., 1989] and we use MOLA data to test the hypothesis. Of the two proposed contacts/shorelines, the younger Contact 2 shows the closest approximation to an equipotential surface; vertical variations along this surface occur in areas with post‐contact‐formation geological activity or suspected changes in the position of an equipotential surface (e.g., Tharsis) with time. The surface of Mars is smoother at all scales below Contact 2 than above. The volume of the region below Contact 2 (∼1.5×10 7 km³) is between the minimum estimated total outflow channel discharge and the maximum estimated megaregolith pore space. These results are consistent with the hypothesis that a large standing body of water occupied the northern lowlands in the past history of Mars.