About the time that life was taking hold on Earth, Mars not only had the ingredients for life as well, but long-lived lakes that could support it, new research from NASA's Curiosity rover team shows.
Analysis of sediments and geologic features found in the rover's Gale Crater landing site show that the basin periodically filled with water that lasted for hundreds or even thousands of years. Previously, the rover discovered evidence of an ancient shallow lake and streams.
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"You have a deep hole, filled with water that is stable," which indicates that Mars must have had a denser atmosphere at that point in its history than can be explained by current computer models, geologist John Grotzinger, with the California Institute of Technology, told Discovery News.
"It also means that other places were wet as well," he added.
The new research "strongly bolsters the case that if life ever did evolve on Mars there would have been many habitable environments," Grotzinger said. "This is the definitive evidence that you need to say that lakes were stable on Mars."
The study, published in this week's Science, not only proves that impact craters can -- and indeed did -- fill with water, but also settles debate about how Mount Sharp, a three-mile high mound of sediment rising from the floor of Gale Crater, formed.
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Analysis of data collected by the rover shows that water collected on the crater's floor, which gradually rose over time until the basin was completely filled.
"The only way to get that is to have a body of standing water that receives sediment and fills the lake. Then the water rises and that creates more space for sediment to accumulate again and again. In that fashion, like a dipstick rising, you see the crater progressively filling up layer after layer after layer after layer after layer until it goes up to 1,000 meters, maybe 2,000 meters, then stops," Grotzinger said.
Then a new cycle began, this time driven by winds. The layers of sediment eroded away until all that was left was a mountain in the middle of the crater.
Scientists estimate the crater filled and eroded within a span of about 500 million years approximately 3.2 billion to 3.7 billion years ago, a period of time that overlaps with the oldest sedimentary rocks on Earth.
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"I've been surprised, pleasantly surprised, by the similarities between Earth and Mars," University of Utah geologist Marjorie Chan told Discovery News.
"Although there is not yet definitive evidence for extraterrestrial life, the geologic results show that there were the key ingredients of water and places where water could have been accessible for microbial life to originate and evolve," on Mars, she noted in Science essay about the Curiosity team's findings.
"The geology of Mars still holds the tantalizing possibility that extraterrestrial life might exist or have been preserved because the evidence of water is so plentiful," she said.