Ancient Lakes on Mars Confirmed by Curiosity Rover Team

NASA's Curiosity Rover Team Confirms Ancient Lakes on Mars

NASA's Curiosity Rover team announced that Mars was once, billions of years ago, capable of supporting standing water lakes -- perhaps for as long as 500 million years. 

Ancient Lakes on Mars

Illustration depicting a lake of fresh water partially filling Mars' Gale Crater. Gale hosted a series of such lakes that each persisted for hundreds to tens of thousands of years at a time, a new study suggests. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

Using data from the Curiosity rover, the team has determined the sediment in the Gale Crater, where the rover landed more than three years ago, was deposited from a lake that filled the crater. The sediment deposited as layers, forming the foundation of the mountain that today sits in the middle of the crater -- Mount Sharp.

​Ashwin Vasavada, Mars Science Laboratory project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and co-author of the new Science article to be published Friday, Oct. 9, said it this way:

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. 

When you add these findings into the recent announcement that water currently flows on Mars, the idea of Mars as a wet planet gets stronger and stronger.

Michael Meyer, lead scientist for NASA's Mars Exploration Program at NASA Headquarters in Washington, said:​

What we thought we knew about water on Mars is constantly being put to the test.  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.

The idea that the Gale Crater had filled with layers of sediment is not new. Before Curiosity, some scientists speculated the deposits were "dry" -- accumulated from wind-blown sand and dust -- while others considered the possibility of lakes on Mars and water-based deposition.

The latest results from Curiosity 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.

Vasavada added:​

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.  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.
Mudtones deposits

Mudstone? Credit: NASA

On Earth, mudstone indicates the presence of standing water, like lakes,  that remain for a long time.   Vasavada thinks the sediment that eventually formed the lower portion of the Mount Sharp comes from the same process.

​John Grotzinger, the former project scientist for Mars Science Laboratory at the California Institute of Technology in Pasadena, and lead author of the new report, says:

Paradoxically, where there is a mountain today there was once a basin, and it was sometimes filled with water.  We see evidence of about 250 feet (75 meters) of sedimentary fill, and based on mapping data from NASA's Mars Reconnaissance Orbiter and images from Curiosity's camera, it appears that the water-transported sedimentary deposition could have extended at least 500 to 650 feet (150 to 200) meters above the crater floor.

The total thickness of sedimentary deposits in Gale Crater indicate the water could have extended higher still, perhaps up to one-half mile (800 meters) above the crater floor. Above that height,  Mount Sharp shows no evidence of hydrated strata.

No one is quite sure what the original source of the water was that carried sediment into the crater, or other lakes on Mars for that matter. For flowing water to have existed on the surface, Mars must have had a thicker atmosphere and warmer climate than today.

Related: NASA issues new Challenge for using Martian resources​

At least some of the water may have been supplied to the lakes by snowfall and rain in the highlands of the Gale Crater rim. Some have made the argument that there was an ocean in the plains north of the crater, but that does not explain how the water managed to exist as a liquid for extended periods of time on the surface.

As Grotzinger put it:​

We have tended to think of Mars as being simple.  We once thought of the Earth as being simple too. But the more you look into it, questions come up because you're beginning to fathom the real complexity of what we see on Mars. This is a good time to go back to reevaluate all our assumptions. Something is missing somewhere.

More information about Mars Science Laboratory is online at:

​http://www.nasa.gov/msl

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