About Mars Exploration Rovers

The names for the Mars Exploration Rovers - Spirit and Opportunity - were selected from nearly 10,000 entries in a contest sponsored by NASA, the Lego Company, and the Planetary Society. 9-year-old Sofi Collis, in the winning essay, wrote, "In America, I can make all my dreams come true. Thank you for the 'Spirit' and the 'Opportunity.'"

The two identical rovers were originally thought to be able to trek up to 100 meters a day ("sol") across the martian surface, but on March 31, 2005 Opportunity traveled a distance of 220 metersin a single day. This is farther than the 1997 Mars Pathfinder rover Sojourner's travel throughout its entire mission. Each rover carries a sophisticated set of instruments – the Athena Science Payload – that has allowed it to search for evidence of liquid water in the planet's past.

On June 10, 2003, the first Mars Exploration Rover (MER) spacecraft Spirit was launched on a Delta II rocket from Cape Canaveral, Florida. After a seven month flight, it entered the martian atmosphere in January 3, 2004. The second lander and rover, Opportunity, followed on January 24.

The rovers each had a spectacular landing, similar to that of the Pathfinder spacecraft. After entering the atmosphere, the rovers deployed their parachutes and airbags, hitting the surface with enough force to bounce back up a hundred feet in the martian air. After finally settling down, the lander petals opened to reveal the rovers folded inside like origami. The rovers had to unfold themselves carefully, deploying their camera masts, antennae, wheels, and solar arrays.

The landing portion of the mission featured a design that is dramatically different from that of Mars Pathfinder. Where Pathfinder had a lander and the small Sojourner rover, each MER spacecraft carried just a large, long-range rover. The rover has a mass of nearly 180 kilograms (about 380 pounds).

Each rover can take a 360-degree visible color and infrared image panorama. Athena scientists can choose rock and soil targets and command the rovers to explore their surroundings.

The landers have long since been left behind, as both Spirit and Opportunity have searched out enticing clues in the soil.

When a rover reaches a target, its multi-jointed arm deploys and the target is examined with a microscope and two spectrometers. The "RAT" (Rock Abrasion Tool) is used to expose fresh rock surfaces for study. Images and spectra of interesting rocks and soils are taken daily.

It was originally believed that the rovers would only have the solar power capability to last for around 90 sols, or the early summer of 2004, but regular "cleaning events" and careful maneuvering have already allowed them to continue for more than three years!

Image and Text Credit: NASA/JPL/Cornell