Categories: Mars

Mars Rover Opportunity Blueberry Geological Mystery

NASA — The long-lived rover Opportunity has returned an image of the Martian surface that is puzzling researchers.

Spherical objects concentrated at an outcrop Opportunity reached last week differ in several ways from iron-rich spherules nicknamed “blueberries” the rover found at its landing site in early 2004 and at many other locations to date.

Opportunity is investigating an outcrop called Kirkwood in the Cape York segment of the western rim of Endeavour Crater. The spheres measure as much as one-eighth of an inch (3 millimeters) in diameter. The analysis is still preliminary, but it indicates that these spheres do not have the high iron content of Martian blueberries.

“This is one of the most extraordinary pictures from the whole mission,” said Opportunity’s principal investigator, Steve Squyres of Cornell University in Ithaca, N.Y. “Kirkwood is chock full of a dense accumulation of these small spherical objects. Of course, we immediately thought of the blueberries, but this is something different. We never have seen such a dense accumulation of spherules in a rock outcrop on Mars.”

The Martian blueberries found elsewhere by Opportunity are concretions formed by action of mineral-laden water inside rocks, evidence of a wet environment on early Mars. Concretions result when minerals precipitate out of water to become hard masses inside sedimentary rocks. Many of the Kirkwood spheres are broken and eroded by the wind. Where wind has partially etched them away, a concentric structure is evident.

Opportunity used the microscopic imager on its arm to look closely at Kirkwood. Researchers checked the spheres’ composition by using an instrument called the Alpha Particle X-Ray Spectrometer on Opportunity’s arm.

“They seem to be crunchy on the outside, and softer in the middle,” Squyres said. “They are different in concentration. They are different in structure. They are different in composition. They are different in distribution. So, we have a wonderful geological puzzle in front of us. We have multiple working hypotheses, and we have no favorite hypothesis at this time. It’s going to take a while to work this out, so the thing to do now is keep an open mind and let the rocks do the talking.”

Just past Kirkwood lies another science target area for Opportunity. The location is an extensive pale-toned outcrop in an area of Cape York where observations from orbit have detected signs of clay minerals. That may be the rover’s next study site after Kirkwood. Four years ago, Opportunity departed Victoria Crater, which it had investigated for two years, to reach different types of geological evidence at the rim of the much larger Endeavour Crater.

The rover’s energy levels are favorable for the investigations. Spring equinox comes this month to Mars’ southern hemisphere, so the amount of sunshine for solar power will continue increasing for months.

“The rover is in very good health considering its 8-1/2 years of hard work on the surface of Mars,” said Mars Exploration Rover Project Manager John Callas of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Energy production levels are comparable to what they were a full Martian year ago, and we are looking forward to productive spring and summer seasons of exploration.”

NASA launched the Mars rovers Spirit and Opportunity in the summer of 2003, and both completed their three-month prime missions in April 2004. They continued bonus, extended missions for years. Spirit finished communicating with Earth in March 2010. The rovers have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life.

NASA RELEASE : 12-32

Dan Mantel - KnowledgeOrb Contributor

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Nonon says:

September 30, 2012 at 11:19 am

Further to my remarks about wind speed on the pruveois thread I found this on the JPL Marsdata site: Surface winds on Mars are mostly gentle, with typical speeds of about 6 miles (10 kilometers) per hour. Scientists have observed wind gusts as high as 55 miles (90 kilometers) per hour. However, the gusts exert much less force than do equally fast winds on Earth. The winds of Mars have less force because of the lower density of the Martian atmosphere (which is about 1/100 that of Earth). So the rocks we see here may well be in situ that is, they're sitting right where they landed when the cataclysmic event that threw them there occurred. Probably those chips around the rock were broken off then too, from impact and perhaps cooling stress. After all, even 90 kmph winds won't move much more than fine sand given an atmospheric pressure of 1/100th of ours.So? Well, geologists on Earth have a hard time finding evidence of certain kinds of past cataclysms, and therefore come up a little short in their understanding of these forces. But on Mars, in many cases it seems, the evidence is just lying there waiting for us to come see it and measure and photograph and speculate and . What fun we'll have. As well, it is beginning to look as if those SF stories featuring the risk of wind storms on Mars may have overstated the case. Wind should be a minor problem, though the fine dust it raises will almost certainly be an irritant, perhaps a major one.