Small spherical objects fill the field in this mosaic that combines four images from the Microscopic Imager on NASA’s Mars Exploration Rover, Opportunity. The view covers an area about 2.4 inches (6 centimeters) across, at an outcrop called “Kirkwood” in the Cape York segment of the western rim of Endeavour Crater. The individual spherules are up to about one-eighth inch (3 millimeters) in diameter.
The Microscopic Imager took the component images during the 3,064th Martian day, or sol, of Opportunity’s work on Mars (Sept. 6, 2012).
Opportunity discovered spherules at its landing site more than eight-and-a-half years earlier. Those spherules were nicknamed “blueberries.” They provided important evidence about long-ago wet environmental conditions on Mars because researchers, using Opportunity’s science instruments, identified them as concretions rich in the mineral hematite deposited by water saturating the bedrock.
The spherules at Kirkwood do not have the iron-rich composition of the blueberries. They also differ in concentration, distribution, and structure. Some of the spherules in this image have been partially eroded away, revealing concentric internal structure.
Opportunity’s science team used the rover for further investigation of these spherules to determine what evidence they can provide about ancient Martian environmental conditions. 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.