Possible erosion marks of bottom oceanic currents in the northern lowlands of Mars

Abstract

There has been much interest for the hypothetical ancient ocean which might have resided in the northern lowlands of Mars. Hints are the global subdivision of Martian crust, the smooth appearance of the northern terrains, the elevation of river deltas, and the past shorelines. Here it is suggested that water in a sufficiently deep northern ocean would have likely formed water currents similar to those occurring in the ocean on Earth.Numerous furrows in the northern lowlands are interpreted as the erosion marks of former water currents and shown to reasonably match the expected orientation on a rotating planet. The direction of furrows indicates that whereas some of the currents were directed down-slope (being thus driven by slight gravity differences like in a turbidity current of hyperpycnal flow), others were nearly parallel to the contour lines. It is suggested that the latter could correspond to the scars of ancient Martian currents similar to contour currents occurring in the oceans of the Earth, a kind of low-density oceanic flow in which gravity is balanced by the Coriolis force. Contour currents are particularly relevant for assessing the Martian ocean, as they are characteristic of the oceanic environment and cannot be formed by subaerial processes.