Three billion years ago, you could have stood on Mars and watched a river spill into a sea. That picture is still speculative, but new evidence makes it harder to dismiss. Researchers at the University of Bern, working with the INAF; Osservatorio Astronomico di Padova, report that they have identified landforms near Valles Marineris that closely match river deltas on Earth. The features sit near the southeast portion of Coprates Chasma, part of the planet’s largest canyon system. The team argues these deposits mark where rivers once entered a standing body of water, likely an ocean. Their study appears in the journal npj space exploration. A coastline emerges from orbital images You have seen Mars described as dry and red. Yet orbiters keep revealing signs of earlier water, including minerals altered by water and layered sediments that hint at lakes. Valles Marineris, a canyon chain stretching more than 4,000 kilometers, has been a major target in that search. Map of Southeast Coprates Chasma’s promontory. (CREDIT: npj Space Exploration) In this work, the Bern-led group used …