Mars' Ancient Oceans: Continental Shelves, Not Bathtub Rings

The decades-long search for a Martian 'bathtub ring' to prove the existence of ancient oceans has yielded ambiguous results due to distorted shorelines. A new study proposes that scientists should instead focus on identifying continental shelves, which are more prominent features of oceans on Earth. Researchers found a vast Martian shelf spanning 10.2 million square kilometers, with an elevation range of -1,800 to -3,800 meters. This shelf contains known deltas, shorelines, and layered rock formations, supporting the theory of a past ocean. The warped shorelines are attributed to extreme sea-level fluctuations, up to eight times larger than Earth's glacial cycles, caused by the absence of tectonic plate recycling. Data from the Zhurong rover, detecting subsurface sediment layers similar to Earth's coastal deposits, further bolsters this hypothesis. Future missions, such as the Rosalind Franklin rover, will explore areas within the proposed shelf line, potentially uncovering more evidence of Mars' watery past and its implications for habitability. The shift in focus from shorelines to continental shelves represents a significant advancement in understanding Martian geological history and the search for past life.

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