When NASA's Perseverance rover arrived at the inner edge of Jezero Crater in September 2023, mission scientists did not expect what the rocks would show. The area, known as the Margin Unit, runs along the shoreline of an ancient Martian lake, so it seemed like a promising place to look for signs of a single long-lived watery past.
Instead, the early Martian rocks preserved there reveal at least three separate water episodes. That suggests the lake and its surroundings were shaped by multiple distinct wet periods rather than one continuous environment.
The findings add nuance to the story of water on early Mars and raise new questions about how the landscape evolved over time. The results come from a single source, so there is no conflicting interpretation to compare against yet.