NASA's Perseverance rover has discovered evidence of surprisingly complex water interactions on ancient Mars, contradicting earlier expectations about the planet's hydrology.
When the rover reached the inner edge of Jezero Crater in September 2023, scientists expected to find sedimentary rocks formed by layers of sand accumulating over millennia. Instead, they discovered igneous rock—the kind formed from magma deep underground or volcanic activity at the surface. These rocks, however, preserved a detailed record of water activity. The rocks showed evidence of having interacted with water on at least three separate occasions, with each encounter further altering their chemistry and appearance. Scientists made the discoveries using SuperCam, an instrument on the rover's mast that fires a laser up to 21 feet away to determine the mineral composition of rocks based on the light they reflect. The findings were published Monday in the journal Communications Earth & Environment.
In the first water event, carbon-dioxide-rich groundwater reacted with olivine, a magnesium and iron mineral, creating carbonate-filled ridges in bedrock fractures. A second event, possibly related to an ancient lake in the crater, deposited silica minerals. A third, later event produced mineral veins including calcium sulfate and fluorite at one location, indicating hot water circulating through volcanic rocks.
"Before we arrived at the Margin Unit, the main hypothesis derived from orbital observations was that the carbonate seen from orbit formed from interaction with the lake that existed in Jezero Crater," said Candice Bedford, a research scientist at Purdue University and the study's lead author. "But now we know that this location became a sort of crossroads for aqueous systems."
Perseverance examined more than 185 bedrock targets across the area, which spans approximately 870 feet of elevation. The discovery suggests Mars had a more complex water history than previous orbital observations indicated, with implications for understanding the planet's past climate and potential habitability.