NASA's Opportunity rover has determined that a strange bubbly rock on the surface of Mars is actually a meteorite, offering a new clue into how the martian surface is made and remade.
Scientists are not so much interested in the meteorite itself. Rather, they want to see if other objects nearby also are meteorites and how martian winds are reshaping the planet.
If sand is continually blowing in and being deposited on the surface, burying things and building up terrain over time, meteorites will be covered and few will be seen, rover mission scientist Steve Squyres (search) said Tuesday.
"I didn't see this one coming," Squyres said. "I try very hard to anticipate the things that we might find and the things we might need to know, and be prepared for things, but an iron meteorite was not something that I was expecting."
But if fine surface material is being continuously stripped away by the wind, coarse things such as meteorites will be left behind and their accumulation will show.
"So whether you're seeing a net accumulation or a net burial of the meteorites is going to tell you something about what the erosion or deposition rates are out on the plains," Squyres said.
Opportunity, a six-wheeled robot geologist, quickly discovered rocks showing that its area of Meridiani was once soaked in water, the major scientific finding of the twin-rover mission.
After that it explored rocks in a deep crater before heading off to give engineers a look at its discarded heat shield.
A strange basketball-sized object nearby stood out immediately.
It looked like nothing seen at either landing site, said Squyres, a Cornell University scientist who is the principal investigator for NASA's Mars Exploration Rovers (search) mission. Scientists suspected it was a meteorite.
"On a mission of exploration, some things you're going to find because you went looking for them, you planned for 'em and you did your job right, and sometimes you're just going to get lucky. And this one was just luck," said Squyres.
Opportunity was then ordered to deploy its instrument arm to confirm if the object was a meteorite. The rover used its brush to remove dust but didn't grind into the meteorite since it was determined the tool would be no match for the nickel-iron hunk.
Tests on Earth showed that a similar tool's grinding heads would be worn away by the meteorite.
"We designed our rock abrasion tool for rock. We didn't design it for nickel-iron alloys," he said.
"I've actually told the team that we probably shouldn't linger here long because this is obviously the place at Meridiani Planum where large metal objects fall from the sky," Squyres joked.