Two new studies have been released that illustrate that the dry Martian lakebed that is currently being explored by NASA’s Curiosity rover was home to a habitable environment for over 700 million years, and possibly for well over a billion years.
Combining a wide array of geological and spectroscopic data gathered by Curiosity, the study has pieced together a deep history of Mars’ Gale Crater, showing that the basin was home to an open-water lake for at least 700 million years. The lake warmed early in its history, and stratified layers formed from sediment that settled on the lake bottom. Chemical analysis of the sediments show the presence of oxygen, and later in its history, salt-rich deposits began to dissolve into the water. The study also found that the region was comfortably warm for much of its history, unlike the cold Mars environment we know of today.
"Only a small component of the observed stratigraphy express[es] geochemical properties consistent with a cold climate," the study explains. They estimate that this 700 million year habitable period concluded 3.1 billion years ago, when the lake eventually dried up.
However, a second study picked up on Gale Crater’s post-lake history, and found that things didn’t dry up immediately. After the open water had evaporated out of the lakebed, wind-blown sand began to fill the basin, and eventually began to form into sandstone layers. But before this happened, those same winds had sand-blasted some of the original sedimentary layers away, leaving areas of Gale’s geology bare for Curiosity to record, including patches that exhibit mineral and salt-rich veins that were deposited by water that had seeped into the ground.
The implication here is that this groundwater permeated the ground after both the erosion of the original sedimentary layers and the formation of the new sandstone deposits, a process that would have taken a great deal of time: while the crater might have no longer hosted a lake, there was still water present in the region for millions of years after the lake itself disappeared, meaning that the region could very well have been able to support life for well over a billion years.
We now have evidence that simple forms of life began to appear on Earth a mere 100 to 200 million years after water began to form on the surface here, meaning that life, albeit simple forms of it, would have had an ample amount of time to form in Gale Crater’s environment, and could very well have persisted underground well after the lake itself disappeared.
Perhaps it’s still there?