What did the mars rover opportunity discover on mars that relates to questions about the existence of water on mars?

The Mars rover Opportunity discovered hematite, a mineral that typically forms in the presence of water, in large quantities at Meridiani Planum. Its findings of spherical "blueberries," which are concretions likely formed in watery environments, further supported the idea that liquid water once existed on Mars. Additionally, Opportunity's analysis of sedimentary rock layers indicated past conditions that could have supported microbial life, reinforcing the hypothesis of ancient water on the planet.