NASA's Mars Opportunity rover has arrived at "Matijevic Hill" - a site overlooking the 14-mile-wide Endeavour Crater.
The rover will spend the next several weeks exploring the site's intriguing geological features and has already begun investigating a concentration of small spherical objects reminiscent of the iron-rich spheres (nicknamed "blueberries") that were observed at the rover's original landing site nearly 22 driving miles ago.
The small spheres at Matijevic Hill - up to about an eighth of an inch (3 millimeters) in diameter - boast different composition and internal structure.
Opportunity's science team is currently evaluating a range of possibilities for how they formed. Indeed, the "blueberries" found earlier are concretions formed by the action of mineral-laden water inside rocks, but that is only one of the ways nature can form small, rounded particles.
One working hypothesis, out of several, is that the new-found spherules are also concretions but with a different composition. Others postulate that they may be accretionary lapilli formed in volcanic ash eruptions, impact spherules formed in impact events, or devitrification spherules resulting from formation of crystals from formerly melted material.
"Right now we have multiple working hypotheses, and each hypothesis makes certain predictions about things like what the spherules are made of and how they are distributed," explained Opportunity's principal investigator, Steve Squyres, of Cornell University, Ithaca, NY.
"Our job as we explore Matijevic Hill in the months ahead will be to make the observations that will let us test all the hypotheses carefully, and find the one that best fits the observations."