JPL: Two rovers reach Mars
By Sami Asmar

After Opportunity’s landing, JPL Project Manager Pete Theisinger, right, signals two for two to JPL Director Charles Elachi, left, and NASA Administrator Sean O’Keefe, back left. 

Two small but powerful rovers are moving on surface of the red planet, Mars. Capable of traveling as much as 40 meters (44 yards) in a day, these robotic explorers carry a set of sophisticated instruments to search for evidence of liquid water that may have been present in the planet's past. During the landing of each rover, a parachute deployed to slow the spacecraft, rockets fired to slow it further just before impact, and airbags inflated to cushion the landing. After reaching the surface, the spacecraft bounced about a dozen times prior to stopping and deflated the airbags. The landed spacecraft then opened the petals, revealing the rover. Each spacecraft traveled for about seven months from launch to arrival over a distance of about 300 million miles.
The two rovers are located at two distant sites on Mars. Gusev Crater, the site of the rover named Spirit's landing is thought to contain ancient lake sediments while Meridiani Planum, the site of Opportunity's landing is thought to contain water-formed hematite.
They began reconnaissance of the landing site by taking a 360-degree visible color and infrared image panorama. Then have left the petal structure behind and drove off to begin exploration. They utilize the sun's energy to charge their batteries, which provide the electrical power needed for moving as well as operating the instruments, computers, and radio communication systems. The rovers send their signals directly to earth or to one of the spacecraft orbiting Mars, which relay the information to Earth.
Using images and spectra taken daily from the rovers, scientists will command the vehicle to go to rock and soil targets of interest and evaluate their composition and their texture at microscopic scales. Initial targets may be close to the landing sites, but later targets can be far. Rocks and soils will be analyzed with a set of five instruments on each rover, and a special device called the rock abrasion tool will be used to expose fresh rock surfaces for study. Each rover has a mass of nearly 180 kilograms (about 400 pounds). The prime mission for each rover will last three months on the surface.