PERSEVERANCE ROCKS REVEAL THREE ANCIENT MARS WATER EPISODES

Rocks examined by NASA's Perseverance rover at the edge of Mars' Jezero Crater show signs of interacting with water on at least three separate occasions, according to a study published Monday in the journal Communications Earth & Environment. Mission scientists said they were surprised by what the rover found when it reached the "Margin Unit" in September 2023, an area stretching along the shoreline of an ancient Martian lake. Researchers had expected sedimentary rock, formed from layers of sand over millennia, but instead found igneous rock, which forms deep underground from magma or from volcanic activity at the surface. Candice Bedford, a research scientist at Purdue University in West Lafayette, Indiana, and the study's lead author, said mineral crystals within igneous rocks preserve details about the precise moment they formed, and in this case recorded a complex history of water activity on early Mars.

Mars orbiters had detected strong signals of carbonate minerals in the area, and on Earth such carbonates commonly form in shallow ocean and lake environments capable of supporting life. Bedford said the leading hypothesis before Perseverance arrived, based on orbital observations, was that the carbonate seen from orbit had formed through interaction with the lake that once existed in Jezero Crater. The findings were gathered using SuperCam, an instrument mounted on the rover's mast that determines the mineralogy of geological features from the light they reflect. When scientists identify a target of interest, they can command SuperCam to fire a laser up to 21 feet, or 6.5 metres, away, and the resulting plasma's spectrum reveals the target's chemistry. Using this method, Perseverance has analysed more than 185 bedrock targets across the Margin Unit.

Bedford said the Margin Unit had instead proved to be a crossroads for aqueous systems, with each of the three water encounters further altering the rock's chemistry and appearance. The research adds to the rover's ongoing record of environmental conditions on early Mars, built from data gathered since Perseverance began exploring Jezero Crater. NASA's Jet Propulsion Laboratory, which manages the mission, published the findings alongside the study's release.