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What did the Spirit and Opportunity rovers discover about water on Mars?
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Mars
An especially serene view of Mars (Tharsis side), a composite of images taken by the Mars Global Surveyor spacecraft in April 1999. The northern polar cap and encircling dark dune field of Vastitas Borealis are visible at the top of the globe. White water-ice clouds surround the most prominent volcanic peaks, including Olympus Mons near the western limb, Alba Patera to its northeast, and the line of Tharsis volcanoes to the southeast. East of the Tharsis rise can be seen the enormous near-equatorial gash that marks the canyon system Valles Marineris.
The Spirit and Opportunity rovers were sent to Mars specifically to investigate whether the planet had ever supported liquid water, a key requirement for life. Both rovers successfully found evidence that water existed on the Martian surface in the past.12
The most significant discovery was made by Opportunity, which identified rocks that appeared to have been deposited at the shoreline of an ancient body of salty water. By analyzing the chemical and physical composition of rocks, soil, and dust at their respective landing sitesāGusev crater for Spirit and Meridiani Planum for Opportunityāthe rovers provided compelling evidence that these areas had been significantly altered by water in Mars's history.12