There’s water on Mars. There’s an atmosphere. And there might have been microbial life. The closer we look, the more possible that seems.
A new study in the journal Science reaffirms that idea. Led by Joel Hurowitz from Stony Brook University in New York, scientists examined findings by the Curiosity rover, which is in Gale Crater on Mars. This crater is thought to have sustained a lake about 3.5 billion years ago for a few tens of millions of years.
What they found was that within the lake, there may have been differing levels of oxygen. The deeper portions of the lake may have been devoid of oxygen, while the shallower portions were oxygen-rich.
“This suggests there was a diversity of habitable environments in this lake,” Hurowitz told IFLScience. “If there was microbial life present, those microbes would have had a menu of options to choose from.”
Early in our planet’s history, some life thrived in such poor oxygen conditions. It wasn’t until photosynthetic organisms arose that our atmosphere became more oxygenated. So this research suggests that early Mars very much resembled the early surface of Earth.
Evidence for these findings comes from sediments studied in multiple locations by Curiosity. Some rocks bear the thallmarks of originating in streams and rivers that fed the lake. Others seem to have been in this deep oxygen-poor water, while others are decidedly “rustier”, pointing to more oxidation in the shallower part of the lake.
At the moment, we don’t know exactly how big or deep this lake was. At the center of Gale Crater is a mountain called Mount Sharp, which towers 5.5 kilometers (3.4 miles) above the surface. The lake may have wrapped around this like a moat, or it could even have filled the entire crater.
The findings suggest Mars went through some form of climate change 3.8 billion years ago. This changed the planet from being cool and dry to warm and wet, allowing bodies of water like that in Gale Crater to exist.
That came to an abrupt end about 3.1 billion years ago when the atmosphere was eroded by solar wind, after Mars mysteriously lost its magnetic field. Water on the surface boiled away, eventually leading to the relatively barren planet we see today.
Quite why this happened is still unknown. But this paper further cements the idea that much earlier in the Solar System, our two planets were not wholly dissimilar. One flourished into an oasis of life; the other became a relic of a once habitable world.
“We’re really learning a lot about just how Earth-like Mars was in its ancient past,” said Hurowitz. “It gives us a lot of confidence in the search for signs of microbial life.”