Early Mars rocks reveal at least three separate water episodes

When NASA's Perseverance rover reached the inner edge of Mars' Jezero Crater in September 2023, mission scientists were surprised by what they found. The geologic area, called the "Margin Unit," stretches along the shoreline of an ancient Martian lake, so they expected sedimentary rocks, which would have formed as layers of sand piled on top of each other over millennia. Composed of clay and silt, sedimentary rocks on Earth are good at preserving past microbial life. The scientists were especial