These are some of the sedimentary rocks found by Curiosity. Photo: NASA
The Curiosity rover has discovered a Martian site that researchers believe was once home to an ancient, freshwater lake that may have been able to support life.
The lake, found at a spot called Yellowknife Bay in the Gale Crater, existed around 3.6 billion years ago and could have lasted for hundreds of thousands of years. The Curiosity rover’s analysis discovered sedimentary rocks with evidence of carbon, hydrogen, oxygen, nitrogen, and sulfur, elements that suggest the lake could have sustained life. The findings were published Monday in a series of six papers in the journal Science.
This isn’t the first time scientists, or Curiosity rover for that matter, has found evidence of large bodies of water on Mars. But it is one of the first times scientists have specifically outlined an environment in which life could have survived. Earlier this year, Curiosity discovered evidence of a swift-moving stream that could have once been up to three feet deep, and in January, the European Space Agency’s Mars Express satellite took pictures of what appeared to be a 1,000-mile long ancient river that could have been 1,000 feet deep at some points. In both of those instances, however, the chemical data to suggest life could have lived in either body of water was either insufficient or completely absent.
That’s not the case here, and that’s important.
In one of the papers, Mars Science Laboratory chief scientist John Grotzinger, suggests that microbes could have survived in the lake via chemolithoautotrophy, a process by which microbes break down minerals and rocks to create energy. On Earth, chemolithoautotrophs are common in the hydrothermal vents of the deep ocean and deep inside caves.
“We show here that Gale crater once contained an ancient lake that would have been well suited to support a Martian biosphere founded on chemolithoautotrophy,” Grotzinger wrote.
Such a process would have allowed microbial life to survive in the lake even during dry spells, which the team things were often.
“Episodic drying of this lake environment seems certain over this long time scale if not over shorter spans,” he wrote. “However, even if the lake was dry periodically … the presence of former groundwater—well documented for many ancient Mars phenomena—may have provided a refugium to sustain a chemolithotrophic biosphere.”
Monday’s papers aren’t enough to confirm that there was once life on Mars, but it does seem the most optimistic that reputable scientists have ever been about the possibility. The conditions at Yellowknife Bay were neither too salty nor too acidic to reasonably support life, according to the paper. In fact, the conditions appear to have once been so ripe for life that Grotzinger suggests that “many combinations of terrestrial microbes” that could have once lived there.
Sanjeev Gupta, one of Grotzinger’s colleagues, said in a statement that it’s important to note that the team hasn’t found fossils or anything to prove that there was life on Mars, but that the discovery is a big one.
“We have not found signs of ancient life on Mars. What we have found is that Gale Crater was able to sustain a lake on its surface at least once in its ancient past that may have been favorable for microbial life, billions of years ago,” he said. “It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake’s calm waters, converting a rich array of elements into energy. The next phase of the mission, where we will be exploring more rocky outcrops on the crater’s surface, could hold the key to whether life did exist on the red planet.”