Ancient Mars had long-lasting lakes, rivers: NASA

Washington, Oct 9: Mars harboured long-lasting lakes and water streams about 3.8 to 3.3 billion years ago, boosting the odds that life may have once existed on the Red Planet, scientists, including one of Indian-origin, have found.

Using data from the Curiosity rover, NASA's Mars Science Laboratory/Curiosity team has determined that, long ago, water helped deposit sediment into Gale Crater, where the rover landed more than three years ago.

The sediment deposited as layers that formed the foundation for Mount Sharp, the mountain found in the middle of the crater today.

"Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp," said Ashwin Vasavada, Mars Science Laboratory project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

The findings build upon previous work that suggested there were ancient lakes on Mars, and add to the unfolding story of a wet Mars, both past and present.

Last month, NASA scientists confirmed current water flows on Mars. "It's clear that the Mars of billions of years ago more closely resembled Earth than it does today.

Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at NASA Headquarters in Washington.

Before Curiosity landed on Mars in 2012, scientists proposed that Gale Crater had filled with layers of sediments. Some hypotheses were "dry," suggesting that sediment accumulated from wind-blown dust and sand.

Others focused on the possibility that sediment layers were deposited in ancient lakes. The latest results indicate that these wetter scenarios were correct for the lower portions of Mount Sharp.

Based on the new analysis, the filling of at least the bottom layers of the mountain occurred mostly by ancient rivers and lakes over a period of less than 500 million years.

"During the traverse of Gale, we have noticed patterns in the geology where we saw evidence of ancient fast-moving streams with coarser gravel, as well as places where streams appear to have emptied out into bodies of standing water," Vasavada said.

"The prediction was that we should start seeing water-deposited, fine-grained rocks closer to Mount Sharp. Now that we've arrived, we're seeing finely laminated mudstones in abundance that look like lake deposits," he said.

The mudstone indicates the presence of bodies of standing water in the form of lakes that remained for long periods of time, possibly repeatedly expanding and contracting during hundreds to millions of years. These lakes deposited the sediment that eventually formed the lower portion of the mountain.

The research was published in the journal Science.

PTI