The primary surface mission for Opportunity was planned to last 90 sols. The mission has received several extensions and as of 2006 had passed 900 sols.
From her initial landing, by chance, into an impact crater amidst an otherwise generally flat plain, Opportunity has successfully investigated soil and rock samples and taken panoramic photos of her landing site. Her sampling allowed NASA scientists to make hypotheses concerning the presence of hematite and past presence of water on the surface of Mars.

Following this, she was directed to travel across the surface of Mars to investigate another crater site, Endurance crater, which she investigated from June — December 2004. Subsequently, Opportunity examined the impact site of its own heat shield and discovered an intact meteorite, now known as Heat Shield Rock, on the surface of Mars.

From late April 2005 to early June of that year, Opportunity was perilously lodged in a sand dune, with several wheels buried in the sand. Over a six week period Earth-based physical simulations were performed to decide how best to extract the rover from its position without risking a permanent immobilization of the valuable vehicle. Successful maneuvering a few centimeters at a time eventually freed the rover, which resumed its travels.

Opportunity was directed to proceed in a southerly direction to Erebus crater, a large, shallow, partially buried crater and a stopover on the way south towards "Victoria" crater, between October 2005 and March 2006. It experienced some mechanical problems with its robotic arm.

In over two years of functioning, the rover has traversed over 9,000 meters.•

Opportunity landed in Meridiani Planum at 354.4742°E 1.9483°S (areocentric coordinates), about 24 km downrange (east) of her intended target. Although Meridiani is a flat plain, without the rock fields seen at previous Mars landing sites, Opportunity rolled into an impact crater approximately 20 meters in diameter, with the rim of the crater approximately 10 meters (32 feet) from the rover. NASA Scientists were so excited about landing in a crater that they called the landing a "hole in one." Later, the crater was named Eagle crater. This was the darkest landing site ever visited by a spacecraft on Mars. It would be two weeks before she was able to get a better look of her surroundings.

Scientists were intrigued by the abundance of rock outcrops dispersed throughout the crater, as well as the crater's soil, which appeared to be a mixture of coarse gray grains and fine reddish grains. This sweeping look at the unusual rock outcropping near Opportunity was captured by the rover's panoramic camera. Scientists believe the seemingly layered rocks are either volcanic ash deposits or sediments laid down by wind or water. It was given the name Opportunity Ledge.

Geologists said that the layers—some no thicker than a finger—indicate the rocks likely originated either from sediments carried by water or wind, or from falling volcanic ash. "We should be able to distinguish between those two hypotheses", said Dr. Andrew Knoll of Harvard University, Cambridge, a member of the science team for Opportunity and her twin, Spirit. If the rocks are sedimentary, water is a more likely source than wind, he said.•

These layered rocks measure only 10 centimeters (4 inches) tall and are thought to be either volcanic ash deposits or sediments carried by water or wind. The layers are very thin measuring just a few millimeters thick in some cases.

On January 28 2004, NASA announced that the landing site was being named to honor the seven astronauts of space shuttle ''Challenger'''s mission STS-51-L who were killed when the shuttle exploded shortly after launch on January 28 1986.•

The rover alternately pushed soil forward and backward out of the trench with its right front wheel while other wheels held the rover in place. The rover turned slightly between bouts of digging to widen the hole. "We took a patient, gentle approach to digging", Biesiadecki said. The process lasted 22 minutes.

The resulting trench—the first dug by either Mars Exploration Rover—is about 50 centimeters (20 inches) long and 10 centimeters (4 inches) deep. "It came out deeper than I expected", said Dr. Rob Sullivan of Cornell University, Ithaca, N.Y., a science-team member who worked closely with engineers to plan the digging.•

Two features that caught scientists' attention were the clotty texture of soil in the upper wall of the trench and the brightness of soil on the trench floor, Sullivan said.

By inspecting the sides and floor of a hole it dug, Opportunity is finding some things it did not see beforehand, including round pebbles that are shiny and soil so fine-grained that the rover's microscope can't make out individual particles.

"What's underneath is different than what's at the immediate surface", said Dr. Albert Yen, rover science team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif.•

On April 30, 2004 Opportunity reached Endurance crater, which was known to have many layers of rocks. In May the rover circumnavigated the crater, and made observations with Mini-TES and the panoramic camera. The rock "Lion Stone" was investigated and found to be similar in composition to the layers found in Eagle crater.

On June 4, 2004 mission members announced their intention to drive Opportunity into Endurance, even if it should turn out to be impossible to get back out, targeting the various rock layers that were identified in the pictures from the crater rim. "This is a crucial and careful decision for the Mars Exploration Rovers' extended mission", said Dr. Edward Weiler, NASA's associate administrator for space science. Dr Squyres, principal investigator from Cornell University said: "Answering the question of what came before the evaporites is the most significant scientific issue we can address with Opportunity at this time."•

A first drive into the crater was executed June 8 and Opportunity backed out again the same day. It was found that the angle of the surface was well inside the safety margin (about 18 degrees), and the full excursion towards the rock layer of interest was started. During Sols 134 (June 12), 135, and 137 the rover drove deeper and deeper into the crater, each time executing the drive exactly as planned.

Wispy clouds, similar to Earth's cirrus clouds, were spotted.

Opportunity spent roughly 180 sols inside the crater, before backing out of it again in late December 2004.

Victoria crater is a massive impact crater approximately 7 kilometers from the original landing site. Victoria's diameter is six times larger than Endurance crater. Scientists believe that rock outcrops along the walls of Victoria will yield more information about the geologic history of Mars, if the rover survives long enough to investigate them.


On Sol 951 (September 26, 2006) Opportunity reached the rim of Victoria Crater• and transmitted the first substantial views of Victoria, including the dune field at the bottom of the crater. The Mars Reconnaissance Orbiter recently photographed Opportunity at the rim of the crater. *

Opportunitys total odometry as of sol 959 (October 5, 2006) was 9,406.95 meters (5.85 miles).