Spirit, Opportunity mark nine years of Mars exploration (pictures)

After landing on the surface of Mars nine years ago, the Mars Exploration Rover Spirit used its panoramic camera to take this color image. At the time, it was the highest resolution image ever taken on the surface of another planet, with a full size of 4,000 by 3,000 pixels.

Three weeks later, on January 25, 2004, the Opportunity rover landed. In the intervening years, the two robotic explorers have returned an astounding 303,802 raw images, amassing an unprecedented library of photos from the surface of another planet.

This gallery presents just a few of the hundreds of thousands of images provided by the twin rovers.

On December 9, 2004, NASA's Mars Exploration Rover Spirit brushed dust from the surface and took these magnified images of this rock dubbed Wishstone.

The 5-centimeter circle seen here with the microscopic imager showed darker pieces of material randomly distributed within lighter-colored grains.

On its 332nd sol, or Martian day, on December 8, 2004, NASA's Mars Exploration Rover Spirit looked back and used its navigation camera to capture this image of the path it had traveled.

With its panoramic camera, NASA's Mars Exploration Rover Spirit examined a 50-centimeter rock dubbed Uchben in the Columbia Hills inside Gusev Crater on the rover's 278th Martian day, October 14, 2004.

The rock abrasion tool aboard Spirit cut a 9-millimeter hole in the Clovis rock during the rover's 216th Martian day, August 11, 2004. The hole was at the time the deepest hole ever drilled on Mars.

Brush marks produced by scrubbing the surface of the rock with the abrasion tool's wire brush can be seen as circles on the right side of the image.

Looking southward, the wall of Gusev Crater appears light gray and can be seen rising up against the horizon in this image Spirit captured on its 161st day on Mars, June 16, 2004, with the panoramic camera's blue 750-nanometer filter.

This false-color composite panoramic camera image highlights mysterious and sparkly dustlike material that is created when the soil in this region is disturbed. NASA's Mars Exploration Rover Spirit took this image on its 165th day on Mars, June 20, 2004, in Hank's Hollow.

From the summit of the windswept plateau of Husband Hill on Martian day 582, August 23, 2005, Spirit looks down into the drifts and outcrops of the Tennessee Valley, a region that Spirit was not able to visit during its climb to the top of the hill.

The approximate true-color image spans about 90 degrees and consists of a series of images captured by the rover's panoramic camera.

The navigation camera on NASA's Mars Exploration Rover Spirit captured this view during the rover's 337th Martian day. Perched on the slope of Husband Hill, the rover had just spent several days examining a rock called Wishstone.

Pointing its cameras skyward, Spirit captured the Martian twilight sky at Gusev crater with the panoramic camera around 6:20 in the evening of the rover's 464th Martian day, April 23, 2005.

The beauty of the twilight is also scientifically useful, allowing the research team to determine how high into the atmosphere the Martian dust extends, and to look for dust or ice clouds.

From its winter outpost at Low Ridge inside Gusev Crater, the Spirit rover took this spectacular, color mosaic of hilly, sandy terrain and two potential iron meteorites. The two light-colored, smooth rocks about two-thirds of the way up from the bottom of the frame have been labeled Zhong Shan and Allan Hills.

These two rocks have unusual morphologies and miniature thermal emission spectrometer signatures that resemble those of a rock known as Heat Shield at the Meridiani site explored by Spirit's companion rover Opportunity. Opportunity's analyses revealed Heat Shield to be an iron meteorite.

Spirit acquired this false-color image on the rover's 872nd Martian day, June 16, 2006, using exposures taken through three of the panoramic camera's filters, centered on wavelengths of 750 nanometers, 530 nanometers, and 430 nanometers. The image is presented in false color to emphasize differences among materials in the rocks and soil.

This image from the front hazard-avoidance camera, the Hazcam, on the Opportunity rover shows the rover's arm extended for examination of a target called Onaping at the base of an outcrop called Copper Cliff in the Matijevic Hill area of the west rim of Endeavour Crater during the 3,163rd Martian day of Opportunity's work on Mars, December 16, 2012.

Layers of exposures of rock are seen at the edge of Home Plate, near targeted rocks known as the Gibson panorama, including Barnhill, Rogan, and Mackey.

This false-color panorama is comprised of 246 separate images using 6 different filters covering 160 degrees on the Pancam during Martian days 748 through 751, February 9 through 12, 2006.

On January 1, 2006, Spirit ushered in the New Year on Earth by taking this striking panorama of rippled sand deposits inside the Gusev Crater on Mars.

The panoramic camera on the Opportunity rover shows an outcrop called Olympia along the northwestern margin of the Erebus crater, which exposes a swath of sulfate-rich sedimentary rocks formed from windblown sediments and some also formed by various environmental conditions.

Opportunity captured this view of its heat shield debris field on January 14, 2005, its 347th day on Mars. The main piece of the heat shield is in the middle of the image, with the smaller flank piece behind it and, on the right, the divot caused by the impact.

Opportunity's navigation camera looks back at Endurance Crater, where it spent 181 Martian days furthering our knowledge of ancient water on Mars. Next, Opportunity spent 25 days investigating a nearby meteorite, as well as the heat shield that protected it on its way through the Martian atmosphere.

Opportunity rover spent about 300 Martian days during 2006 and 2007 traversing the rim of Victoria Crater looking for a good place to enter the crater and capturing images of rock outcrops exposed at several cliffs along the way.

The cliff seen here is known as Cape St. Vincent, approximately 12 meters tall on the northern rim of Victoria crater, near the farthest point along the rover's traverse around the rim.

NASA says Cape St. Vincent's layering provides some of the best examples of meter scale cross-bedding observed on Mars to date. Cross-bedding refers to rock layers that are inclined relative to the horizontal and which are indicative of ancient sand dune deposits.

Opportunity used its front hazard-identification camera to obtain this image of its robotic arm and Victoria Crater in the distance at the end of a drive on the rover's 1,271st Martian day, on August 21, 2007.

Because of sun-obscuring dust storms limiting the rover's supply of solar energy, Opportunity had not driven since Sol 1,232, July 12, 2007. On Sol 1,271, after the sky above Opportunity had been gradually clearing for more than two weeks, the rover rolled 13.38 meters.

On the rover's 956th sol, or Martian day, October 2, 2006, Opportunity turned its navigation camera skyward to capture these wispy clouds in the sky.

Like clouds on Earth, these Martian clouds are probably composed of ice crystals and possibly supercooled water droplets. They are similar in appearance to terrestrial cirrocumulus or high altocumulus clouds. On Earth, such clouds are relatively transient and consist of small, individual cloudlets arranged in rippled patterns. They usually form 6 kilometers to 12 kilometers (4 to 7 miles) above Earth's surface by a process known as convection, during which warm air rises and cools, with clouds condensing from the moist air once it has cooled sufficiently.

These Martian clouds appear to be associated with a broader layer of ice-crystal clouds fanning out toward the upper right of the frames at the end of the movie. This is similar to the occurrence of terrestrial cirrocumulus and altocumulus clouds within layers of cirrus or cirrostratus clouds on Earth. Also apparent in this image are prominent waves in the clouds, a result of the effect of gravity waves on cloud thickness, as on Earth.

Opportunity approaches a rock named Marquette Island, which is believed to be a stony meteorite, during the 2,056th Martian day, or sol, of the rover's mission on Mars, November 5, 2009.

NASA says that as Opportunity crossed a relatively barren plain on its long trek from Victoria Crater toward Endeavour Crater, the dark-toned rock stood out so prominently in more distant views on earlier sols that the rover team referred to it as Sore Thumb.

This is the first view of a target selected autonomously by a spacecraft on Mars. During the 2,172nd Martian day, or sol, of its mission on Mars, March 4, 2010, Opportunity used newly developed and uploaded software called the Autonomous Exploration for Gathering Increased Science, or AEGIS, program to self-choose a target from a wider-angle image.

This image from the navigation camera on Opportunity shows the view ahead on the day before the rover reached the rim of Endeavour crater. It was taken during the 2,680th Martian day, or sol, of the rover's work on Mars.

Opportunity used its navigation camera to record this view in the eastward driving direction after completing a drive on July 17, 2011, that took the rover's total driving distance on Mars beyond 20 miles.

Opportunity drove 407 feet during the 2,658th Martian day, or sol, of the rover's exploration of the Meridian Planum region of Mars. That drive brought Opportunity's total odometry to 20.01 miles. It also brought Opportunity within about eight-tenths of a mile (1.3 kilometers) of the rim of Endeavour crater, which has been the rover team's long-term destination for Opportunity since mid-2008. Portions of the Endeavour rim are visible on the horizon in this image.

As of January 2013, Opportunity and its rover twin Spirit have been on Mars, collecting stunning images and scientific data, for 9 years. The original prime missions were slated for just three months, and were easily completed in April 2004.

Both rovers have continued for years collecting extended data and returning more than 303,802 raw images. Spirit became trapped in soft soils and was sadly declared "irrecoverably obstructed" on January 26, 2010. The rover continued operating as a stationary science platform until communication with Spirit failed completely on March 22, 2010. NASA's Jet Propulsion Laboratory continued to attempt to regain contact until May 24, 2011, when it announced that efforts to communicate with the unresponsive rover had ended. But Opportunity continues to return images and data to this day.

Want more Mars? You can access all of Opportunity's 175,578 raw images here, and all of Spirit's 128,224 raw images here.