Opportunity’s second venture was into a deep crater called Endurance, and it later spent two Earth years exploring Victoria Crater. Again, both yielded signs of Mars’ watery past. Endurance’s cliffs showed layers of rock, some laid down in watery times and others during dry periods, showing a varied history of Martian water. More hematite dotted Victoria Crater’s ridge, indicating it had been thrown there during the impact that formed the crater. Scientists think that these minerals formed underground, suggesting that water soaked through the surface and stayed there long enough to form the minerals. All of this water would have been salty and acidic.

Freshwater Find