Evidence that a vast ocean may have covered one-third of the surface of Mars some 3.5 billion years ago gives new support to the idea that the planet may once have harbored life.
A study conducted by University of Colorado at Boulder scientists analyzed water-related features including delta deposits and river valleys to look for evidence of an ocean sustained by a global hydrosphere.
More than half of the 52 river delta deposits - each fed by numerous river valleys - likely marked the boundaries of the proposed ocean, since all were at about the same elevation.
Twenty-nine of the 52 deltas were connected either to the ancient Mars ocean or to the groundwater table of the ocean and to several large, adjacent lakes, researcher Gaetano Di Achille said.
The study implies that ancient Mars probably had an Earth-like global hydrological cycle, including precipitation, runoff, cloud formation, and ice and groundwater accumulation.
And long-lived oceans may have provided an environment for microbial life to take hold on Mars.
"On Earth, deltas and lakes are excellent collectors and preservers of signs of past life," said Di Achille. "If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past."
The team used a geographic information system to map the Martian terrain, and concluded the ocean would have covered about 36 percent of the planet and contained about 124 million cubic kilometers of water.
A second study detected roughly 40,000 river valleys on Mars -about four times the number previously identified. "The abundance of these river valleys required a significant amount of precipitation," said assistant professor Brian Hynek.
"One of the main questions we would like to answer is where all of the water on Mars went," said Di Achille.