Anyone have a pic of the mystery rock?
Just as Spirit has gone up, so its twin Opportunity has gone down, rolling more than 32 feet (10 meters) into Endurance Crater at Meridiani Planum.
"In terms of depth, we've pretty much reached the end of the line," Squyres said, adding that only blueberries and sand dunes - which could end Opportunity's science mission if it were to bog down one - lie ahead. "We built a wonderful rover, but we didn't build a dune buggy."
But that hasn't stopped Opportunity from making a pair of perplexing finds. The rover has found lumpy, odd rock unlike anything its seen to date. Researchers hope to swing by the rock on the way out of Endurance for further study.
"It could just be one big mass of concretions," Squyres said. "I just don't know."
On top of that, Opportunity's robotic arm-mounted Microscopic Imager has detected small, red objects that researchers don't yet understand.
"We have no idea what it was," said Zoe Learner, a science team member and graduate student from Cornell who has studied Mars' blueberry formations.
The red formations are coarse, not always round and some of them appear to have even smaller objects weathering out of them, she said. They may be a kind of red-coated blueberry or an altogether type of concretion, but more study is needed, she added.
Meanwhile, researchers are also considering sending Opportunity to the edge of a nearby tendril of sand dunes, but only if it won't endanger the robot.