Mars today is an arid, inhospitable desert. But billions of years ago, it might have looked a lot like Earth, with liquid water flowing on its surface. Now, new analysis of data from the Persistence rover confirms that Jezero Crater, where the rover is currently exploring, was once a large lake and was even subject to flash floods. The presence of water supports the possibility that life could once have blossomed on Mars.
The analysis is based on images of rocks at the western edge of Jezero Crater, which appears to be a river delta. Here the layers of sediment are laid out in a fan shape that resembles a river delta on Earth where a river flows into a lake. An international team of researchers found that sedimentary layers confirm the presence of an ancient lake that was calm in its early life but flooded dramatically later.
“If you look at these images, you’re basically looking at this epic desert landscape. It’s the most deserted place you could ever visit.” said Benjamin Weiss, professor of planetary science in MIT’s Department of Earth, Atmospheric and Planetary Sciences and a member of the analysis team. “There is not a drop of water anywhere, and yet, here we have evidence of a very different past. Something very deep has happened in the history of the planet.”
The researchers were able to tell that significant flooding was caused by the presence of boulders up to 1 meter large, which were embedded in the smaller layers of the delta. These large boulders may have come from outside the crater, which has covered 40 miles or more by heavy flooding. The fact that they sit on top of many older layers indicates that the flood may have occurred late in the lake’s history.
“You need energetic flood conditions to move the big and heavy rocks,” Weiss said. “This is a special thing that could indicate a fundamental change in the local hydrology or perhaps the regional climate on Mars.”
Researchers have long assumed that Jezero was once a lake, hence the choice of location for persistence, but this could not be fully confirmed until the rover visited the site and collected data. . Now, they can be sure that there once was abundant water and it was present long enough for life to potentially emerge.
“We now have the opportunity to look for fossils,” said team member Tanja Bosak, a professor of geobiology at MIT. “It will take some time to get to the rocks that we expect to actually sample for signs of life. So, this is a marathon, with great potential.”
The findings are published in the journal Science.