A 3.5 billion-year-old freshwater lake on Mars, now dry, may have been an ecosystem where life could thrive, according to an analysis of data collected by NASA’s Curiosity rover.
Though Mars is now cold, rocky and sterile, it was once warmer and wetter. The lake that may have fostered microbial life is now the crater where the National Aeronautics and Space Administration’s Curiosity landed in 2012, according to six papers presented at the American Geophysical Union in San Francisco and published online in the journal Science.
The discovery was made from a series of rocks at a site called Yellowknife Bay. The rocks, called mudstones, revealed that what is now Gale Crater held at least one lake 3.5 billion years ago. The trace elements suggest it was freshwater, with other elements such as carbon, hydrogen, nitrogen and sulfur -- microbial snacks.
The lake at Gale Crater and its feeder sources of water “would have provided a fairly long-lived, habitable environment for microorganisms that could have lasted for tens of millions of years,” John P. Grotzinger, a California Institute of Technology geology professor and lead author of one of the reports released yesterday, said in a telephone interview.
The lake was probably the size of one of the smaller Finger Lakes in upstate New York, with the “depth of a swimming pool,” Grotzinger said. The environment likely was cold, with ice coming and going on the surface. From time to time, the lake probably dried up, he said.
Now that the scientists know the planet could have harbored life, “we’ve turned a conceptual corner,” Grotzinger said.
Curiosity next will seek signs of organic carbon because that often is a sign of past microorganisms that have decayed, he said. That task will be challenging, because it’s hard to preserve the carbon, especially in an environment like Mars, which receives a great deal of radiation.
The conditions may have allowed for the rise of kinds of bacteria called chemolithoautotrophs, which draw energy by breaking down rocks and minerals. On Earth, these bacteria can be found in mines dug deep into the surface; they are also found in caves and hydrothermal vents, the researchers said.
“I wouldn’t be shocked if these things ever got started that they’re still there, hundreds of meters below the surface,” said Crotts, who wasn’t involved in the report.
The Mars Science Laboratory, the formal name of the mission deploying Curiosity, was launched from Cape Canaveral in Florida, on Nov. 26, 2011. NASA chose the Gale Crater because of evidence that there had been water in the past. The mission was conceived to find conditions that might support microbial life.
At the bottom of the crater, the mission found clay minerals, which form in water that isn’t too basic or acidic.
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