NASA’s steady reconnaissance of Mars with the Curiosity rover has produced another major discovery: evidence of an ancient lake — with water that could plausibly be described as drinkable — that was part of a long-standing, wet environment that could have supported simple forms of life.
Scientists have known that the young Mars was more Earthlike than the desert planet we see today, but this is the best evidence yet that Mars had swimming holes that stuck around for thousands or perhaps millions of years. (It would have been very chilly — bring a wet suit.)
Scientists had announced this year that they’d found signs of an ancient, fresh-water lake within Gale Crater, but the new reports provide a much more detailed analysis, including the first scientific measurements of the age of rocks on another planet. The research suggests that Martian winds are sand-blasting rock outcroppings and creating inviting places to dig into rocks that may retain the kind of organic molecules associated with ancient microbes.
Gale Crater is in an area with rocks about 4.2 billion years old. The lake, which scientists think existed a little more than 3.5 billion years ago, was roughly the size and shape of one of New York’s Finger Lakes. The freshwater lake may have come and gone, and sometimes been iced over, but the new research shows that the lake was not some momentary feature, but rather was part of a long-lasting habitable environment that included rivers and groundwater.
Previous discoveries by Mars rovers had suggested that the Red Planet once had surface and groundwater with the quality of battery acid, but the water in this lake looks much more benign.
“If we put microbes from Earth and put them in this lake on Mars, would they survive? Would they survive and thrive? And the answer is yes,” said John Grotzinger, a Caltech planetary geologist who is the chief scientist of the Curiosity rover mission. He is the lead author of a paper titled “A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars.”
“In March, we did know that we had a lake, but what we weren’t sure of was how big it was and how long it lasted, and also we were not sure about the broader geological context that supports the presence of lakes coming and going for a very long time,” Grotzinger said in an interview.
“This is really similar to an Earth environment,” he said at the AGU news conference.
The duration of this environment matters when it comes to habitability, said Jennifer Eigenbrode, a geochemist at NASA Goddard Space Flight Center and a co-author of three of the new papers.
“If you have it sustained for a while, life can be there and do something and persist,” she said.
The chemistry of the lake would have been congenial to organisms known as chemolithoautotrophs — mineral-eaters. Whether such organisms, which thrive on Earth in exotic environments such as caves and deep-sea hydrothermal vents, actually existed on the young Mars is a question Curiosity lacks the tools to answer.
Source: Washington Post