Over the last ten years the Opportunity rover has done extensive geological surveys on the surface of Mars. Before the rover shut down to ride out the Martian winter, it sent back images of a mystery rock that seemed to appear out of nowhere. The initial results show that the composition of the rock are unlike anything that has been discovered on Mars. The announcement was made last week by lead scientist Steve Squyres during the “10 Years of Roving Mars” celebration at CalTech.

Days on Mars are a little longer than on Earth. They are measured in “sols” and last about 24 hours, 39.5 minutes. Between twelve sols on Mars, a small rock about the size of a fist appeared over a previously-imaged patch of ground. The mystery thrilled scientists and has generated an unprecedented amount of buzz around a rover that has been sending back information from the red planet since 2004. 

Opportunity landed on the surface on January 25, 2004, and will mark its ten year anniversary of operation this Saturday. It was originally only supposed to operate for 90 sols, but has been giving us new information about the surface of Mars for an astonishing 3552 sols. Over the last ten years, Opportunity has traveled almost 23 miles (37 kilometers) on the Martian surface. During that time, Opportunity has provided a wealth of information, but nothing as unpredictable as the emergence of this mystery rock. The small rock has been named “Pinnacle Island” by the Opportunity team. It is very dark red in the middle with white edges, which reminded the crew of a jelly donut. 

Scientists believe that there are two possibilities for the rock’s sudden appearance. It may have been ejected from a meteorite impact nearby and just happened to land directly in the rover’s path. This is the more far fetched idea, because there is no crater or smoke to indicate that there was an impact. Scientists believe that it is far more likely that the rock was flung over to its current location like a Tiddlywink when the rover was maneuvering in the area. 

Before this rock was discovered, the actuator that allows the front right wheel to move had stopped working properly. Scientists believe that when the rover’s wheel was turning on bedrock, the rock became lodged and inhibited movement. The side of the rock that is facing up hasn’t been exposed for billions of years, creating a unique opportunity for the researchers to investigate the rock’s properties. 

Initial reports show that the little jelly donut is different than anything the team has ever encountered on Mars. The rock’s composition is high in potassium and sulfur, with double the amount of manganese of any rock ever described on Mars. The team is currently debating about how this rock fits in to everything they have been studying over the last decade. Squyers relished in the mystery, stating “we will never be finished. There will always be something tantalizing, something wonderful just beyond our reach that we didn’t quite get to – and that’s the nature of exploration.”