NASA's Mars Exploration Rover Opportunity is expected to reach the rim of Endeavour crater on Mars, where its rover twin Spirit finished its 6-year-long mission in May.

Driving commands sent up to Opportunity directed the six-wheel rover to make the final push toward Endeavour crater, a 14-mile-wide depression near the Martian equator that likely could be its final destination, the Associated Press reports.

The finish line for Opportunity, which will reach the crater's edge on Tuesday at earliest, is a site on the rim of Endeavour named "Spirit Point," named by the rover team members in honor of the rover's lost twin.

"Opportunity's

Opportunity's First Goal at Endeavour Crater - 'Spirit Point' (NASA/JPL-Caltech/Univ. of Arizona)

Twin rovers Opportunity and Spirit completed their three-month prime missions on Mars in April 2004. Both rovers went on to extended missions, making important discoveries about the environment on ancient Mars, which suggest possibilities for microbial life.

"Spirit achieved far more than we ever could have hoped when we designed her," said Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers. "This name will be a reminder that we need to keep pushing as hard as we can to make new discoveries with Opportunity. The exploration of Spirit Point is the next major goal for us to strive for."

The milestone triggers the excitement for an adventure back into a mission that amazed the world with colorful portraits of the landscape and the unmistakable geologic discoveries of a warm and wetter past.

Endeavour crater is arguably the most important science target since landing, said Project manager John Callas of the NASA Jet Propulsion Laboratory.

Opportunity will spend several months imaging the rim and interior of the crater, but is not planned to drive across the crater because it could get stuck, said Callas.

Instead, it will traverse south along the rim in search of clay minerals, which scientists suggest forms under wet conditions.

While orbiting spacecraft has extensively studied these clay minerals, Opportunity will mark the first to examine them directly on the ground.

"We will likely spend years at this location," Callas said. "What a destination. It's not just one spot. There's kilometers of interesting geology to explore."

"Opportunity's

Opportunity's Route to Endeavour Crater The yellow line on this map shows where NASA's Mars Rover Opportunity has driven from the place where it landed in January 2004 -- inside Eagle crater, at the upper left end of the track -- to a point approaching the rim of Endeavour crater. The map traces the route through the 2,670th Martian day, or sol, of Opportunity's work on Mars (July 29, 2011). Endeavour crater has been the rover team's destination for Opportunity since the rover finished exploring Victoria crater in August 2008. Endeavour, with a diameter of about 14 miles (22 kilometers), offers access to older geological deposits than any Opportunity has seen before. In honor of Opportunity's rover twin, the team has chosen "Spirit Point" as the informal name for the site on Endeavour's rim targeted for Opportunity's arrival at Endeavour. Spirit Point is the southern edge of a ridge called "Cape York." Farther south on the rim, a ridge called "Cape Tribulation" offers exposures identified from orbit as clay minerals. The base map is a mosaic of images from the Context Camera on NASA's Mars Reconnaissance Orbiter. It is used by rover team member Larry Crumpler of the New Mexico Museum of Natural History and Science, Albuquerque, for showing the regional context of Opportunity's traverse. Opportunity and Spirit completed their three-month prime missions in April 2004 and continued operations in bonus extended missions. The Mars Reconnaissance Orbiter reached Mars in 2006, completed its prime mission in 2010, and is also working in an extended mission. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project and the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington. Malin Space Science Systems, San Diego, built and operates the orbiter's Context Camera. Image credit: NASA/JPL-Caltech/MSSS/NMMNHS