Spirit just can’t help itself. Even stuck in a sand trap from which it will never escape, the Mars rover finds clues that reveal more about the nature of Mars and the water cycle on the Red Planet.
It was earlier this year that NASA gave up on freeing Spirit: With a broken wheel, the rover simply could not extricate itself from the loose terrain that ensnares it. But as the rover team drove Spirit back and forth, it dug deeper and deeper into the Martian ground. Says team member Ray Arvidson:
“We’re driving backwards, the right front wheel doesn’t work, so wherever we went we had to drag it along. It’s like pushing a shopping cart with a bad front wheel. You don’t push it, you pull it, but the wheel has torque.” [Discovery News]
Eventually Spirit broke through the crust, where a bit of luck struck. Before the rover lost communication with Earth, it beamed back enough information to show that the makeup of the soil beneath Spirit suggests that water was there—and not too long ago, either. The Spirit team just published a study about it in the Journal of Geophysical Research.
The newly exposed surface layers include minerals thought to be hematite, silica and gypsum, which don’t dissolve easily in water. But layers of iron sulfate minerals, which do dissolve easily, lie centimeters below the crust. These layers suggest water, maybe in the form of frost or snow, seeped into the ground relatively recently and carried the soluble minerals deeper into the soil. The seepage could have happened during cycles in Mars’ history when the planet tilted further on its axis. [Wired.com]
Furthermore, the team argues, the neat layering suggests that the deposition happened fairly recently, within a few hundred thousand years or so. Otherwise Mars’ howling winds would have had the chance to erode it away.
“Once you freeze that evidence in a rock, it can stay there for a long time,” said Bruce Banerdt, a project scientist for the Mars Exploration Rovers project at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “But you don’t expect to maintain evidence in loose dirt for long periods of time.” [MSNBC]
DISCOVER: Those Mars Rovers Keep on Going and Going…
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Image: NASA/JPL-Caltech/Cornell University