When NASA's Perseverance rover rolled into the "Margin Unit" of Mars' Jezero Crater, scientists expected to find simple lakebed sediments. Instead, they discovered ancient igneous (volcanic) rocks that reveal a much richer and more active past than previously imagined.
A new study published in Communications Earth & Environment by researchers at NASA's Jet Propulsion Laboratory shows that this region was a meeting point for multiple water systems, interacting with rocks on at least three distinct occasions.
Three Distinct Encounters With Water
Using the SuperCam instrument mounted on its mast, Perseverance analyzed over 185 rock targets by firing laser bursts to uncover their chemical makeup. Reconstructing these geological clues revealed a three-stage timeline:
- CO₂-Rich Groundwater: Early in Mars' history, carbon-dioxide-rich groundwater moved through underground rock fractures, creating carbonate minerals. Over time, softer surrounding rock eroded away, leaving behind hard, mineral-filled ridges.
- An Ancient Lake: As a lake filled Jezero Crater, water sat above the rocks and reacted with olivine minerals, producing high concentrations of silica along the shoreline.
- Hot Underground Springs: In a later phase, heated groundwater circulated through volcanic rock, depositing veins of minerals like fluorite and calcium sulfate.
Why These Discoveries Matter
On Earth, reactions between water and olivine produce hydrogen, which can serve as an energy source for microbial life. Furthermore, both carbonate and silica are exceptional at preserving ancient chemical signatures or microbial traces.
Finding groundwater, ancient lake shorelines, and hydrothermal activity all in one location highlights Jezero Crater as a primary target for understanding early Martian climate, habitability, and potential signs of past life.
