Water on Mars: Do submarine cyclic steps exist on the red planet?

Abstract

Abstract Submarine cyclic steps have a significant impact on the evolution of the ocean floor on Earth. These upper-flow regime bedforms should be even more common in Martian reduced-gravity environments. We postulate that, if early Mars had an ocean, cyclic steps would have formed on Martian deltas spreading along the putative ancient shorelines in the northern plains. The main challenge to identifying submarine cyclic steps on Mars is geologic activity, in particular impacts, volcanism, and aeolian erosion, which have erased or modify much of the geomorphic evidence. Even though many Martian deltaic deposits do not bear much resemblance to the original depositional surfaces, we hypothesize that cementation and consolidation of marine sediments had facilitated the preservation of at least some Martian cyclic steps on deltaic deposits. We combine data from several orbital missions at Mars with a literature review and numerical analysis to inspect bedforms near the foreset-bottomset transition of 17 documented deltaic deposits. The most promising piece of evidence for Martian submarine cyclic steps is a linear series of rhythmic long-wavelength bedforms within a channel incised into the upper delta front of the Aeolis Mensae Delta. These bedforms are remarkably similar to their counterparts observed in channels on deltas and deep-water fans on Earth. Moreover, we speculate that two fields of cyclic steps, likely emanating from a crater upstream of the Aeolis Mensae Delta, are a potential example of contemporary cyclic steps and attest to the sporadic presence of flowing water on present-day Mars.

Keywords

• Water on Mars
• Martian ocean
• Delta
• Martian submarine cyclic steps
• Foreset deposit
• Foreset-bottomset transition