River basin provides evidence of ancient ocean on Mars

Sept. 14 (UPI) -- Mars was once home to a giant ocean, new research suggests.

New analysis of the recently discovered river basin Hypanis Valles, the largest on Mars, suggests the presence a giant alluvial plain.

The evidence that significant amounts of water once flowed on Mars is now overwhelming, but scientists can't yet confirm the presence a massive ocean. However, the latest research sediments found at the mouth of the ancient river basin suggest large volumes of water once met a large body of water.

"Our study is not definitive proof for an ocean, but these geological features are very hard to explain without one," Joel Davis, a planetary scientist and postdoctoral researcher at London's Natural History Museum, said in a news release.

Scientists detailed the discovery this week in the journal Earth and Planetary Science Letters.

"A Martian ocean means that Mars probably had a very Earth-like water cycle, with rivers, lakes, and now oceans, all of which probably interacted as part of a planet-wide system," Davis said. "We think this Earth-like hydrological cycle was active about 3.7 billion years ago, and started to shut down sometime after that."

Scientists have previously found delta-like deposits in craters where water likely once flowed into lakes, but the latest research revealed the presence of fan-like deposits enough to have been created by a large river and ocean-sized body of water.

When large volumes of river water hit the ocean, the collision causes the water to slow down, spread out and drop large amounts of sediment.

Hypanis Valles is a possible landing site for NASA's forthcoming ExoMars 2020 rover mission. The rover, designed to look for signs of life, could provide additional clues as to the nature of Mars' ancient water cycle.