THE RED-BLUE PLANET: ‘Significant areas of Mars may have once been covered by water’: Scientists find hidden clue in Spirit rover data.

Researchers reanalyzed measurements collected by Spirit between 2004 and 2010, revealing widespread traces of crystalline hematite and altered magnetite in ordinary Martian soil — iron-bearing minerals that point to ancient chemical changes consistent with interactions between water and rock. The findings suggest liquid water may have been more widespread across Mars than scientists previously thought, according to a statement from Edith Cowan University (ECU) in Australia.

The team combined hundreds of individual measurements from 32 undisturbed soil sites inside Gusev Crater, where Spirit landed in January 2004, creating the most detailed iron-mineral profile yet assembled for typical Martian soil, according to the statement.

“One of the most important discoveries was finding crystalline hematite in ordinary Martian soil,” Paulo de Souza, lead author of the study and an ECU professor, said in the statement. “This mineral’s widespread presence suggests not only that water was present, but that significant areas of Mars may have once been covered by water.”

How much of it remains as ice is the big question.