Ancient Mars hosted long-lived lakes & rivers, NASA’s Curiosity Rover team says

A group of NASA scientists has discovered that, billions of years ago, Mars had a system of long-lasting lakes and water streams, thus proving the Red Planet was once a much more favorable living environment than researchers had previously thought.

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Several freshwater lakes could have existed within Mars’ 96-mile-wide (154 kilometers) Gale Crater for tens of thousands of years or even longer, a new study conducted by scientists from the NASA’s Mars Science Laboratory and Curiosity team suggests.

The study was based on new data from NASA’s Curiosity rover, which was sent to the Red Planet three years ago and landed in the same Gale Crater that is now believed to have once hosted a system of lakes, NASA’s Jet Propulsion Laboratory says.

“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 (JPL) in Pasadena, California, and co-author of the new article published in the journal Science.

Using data from the rover, the team found that sediments covering the bottom of the Gale Crater and making up the foundation of Mount Sharp, which is located in the middle of the crater, were brought to the site by streams of water. 

Before the rover landed on Mars in 2012, researchers believed that the Gale Crater was filled with layers of sediments formed from dust and sand blown into it by the winds. However, the latest analysis of Mount Sharp’s bottom layers show that they were deposited by streams and rivers running into ancient lakes during a period of less than 500 million years, the JPL press release says.

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“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,” Ashwin 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 added.“Paradoxically, where there is a mountain today there was once a basin, and it was sometimes filled with water,” said John Grotzinger, the former project scientist for the Mars Science Laboratory at the California Institute of Technology in Pasadena, a former member of the Curiosity team, and lead author of the new report.

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“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,” he added.                 

Cradle of life 

The scientists believe that the individual lakes were transient, i.e. they periodically dried out and then filled up again over time, although they claim that the system of lakes and river-like streams inside the crater existed for a long time. 

According to the team, such conditions could make the existence of the germ of life on Mars much more likely.

“Even if the lake goes away, there’s still going to be a groundwater table,” John Grotzinger told Space.com.

“If life had evolved on Mars, you now have a habitat which is perpetually wet that would allow microbes to be sustained. Those environments would have existed probably for millions, if not tens of millions of years throughout the rocks that we see,” he added.

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Mysterious water source

The team also analyzed photos provided by the Curiosity rover that were taken throughout its 5-mile-long (8 km) traverse from its landing site to Mount Sharp, which took more than a year (from July 2013 to September 2014).

The photos demonstrated evidence of river, delta, and lake environments within the Gale crater that formed 3.8 billion years ago after a massive meteor impact.The scientists believe that the lake-and-stream system existed in the crater about 3.5 billion years ago, with the rivers possibly streaming from the northern rim of the Gale to the lake in its center, where Mount Sharp is located now, the study says.

It is unclear, how deep the lake was, although Grotzinger suggested a possible maximum depth in the “tens of meters” range.The original source of water that formed the rivers and lakes in the crater is still a mystery to the scientists, as Mars now has no stable liquid surface water. However, researchers have recently announced that the dark, seasonal streaks that appear on Mars’ surface may come from briny water flows.

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Additionally, in order to host a long-lasting system of lakes and rivers filled with liquid water, Mars must have had a thicker atmosphere and warmer climate than was hypothesized earlier.

Researchers now believe that water either got to the Gale Crater’s rim from snow and ice condensed out of the atmosphere or from an ocean that could have possibly existed on Mars’ extensive northern plains not far from the crater at the same time as the lake and stream system in the Gale.

“If there was some type of a northern ocean, that would be a very convenient way to get water vapor and moisture on the northern rim to generate the very localized deposits we see in Gale Crater itself,” Grotzinger said, as quoted by Space.com.

The scientists are now hoping that further evidence from the Curiosity Rover will help them understand what happened to Mars’ surface water, as well as to the Red Planet’s climate, as the rover is now climbing up through Mount Sharp’s lower reaches to the layers of the mountain that reportedly have never interacted with water and really were formed from wind-blown dust and sand.

“We have tended to think of Mars as being simple,” Grotzinger said. “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,” he added.