NASA's twin robot geologists, the Mars Exploration Rovers, launched on June 10 and July 7, 2003, in search of answers about the history of water on Mars. They landed on Mars January 3 and January 24 PST, 2004. Both rovers made important discoveries about wet environments that could have supported microbial life on ancient Mars. Spirit stopped communicating with Earth in 2010. Opportunity is continuing to provide scientific results, and currently is investigating the rim of a crater 14 miles (22 kilometers) wide.
Here are a few recent photos that were sent back to Earth from Opportunity.
Opportunity has travelled across the Martian landscape more than 24 miles (39 km) and has sent nearly 190,000 images back to Earth. Spirit only roved 4.8 miles, but sent back more than 100,000 images when it was still operational.
On February 14, 2014, the spacecraft still in orbit around Mars captured a photo of Opportunity's "footprints" on a ridge, as well as the rover itself.
You are now invited to go to Mars, thanks to Opportunity.
The "blueberries" are actually hematite spheres. Scientists believe that these only form in the presence of water.