Launch Date June 10, 2003 | 17:58:46 UT
Launch Site Cape Canaveral, Florida, USA
Destination Mars
Type Rover
Status Successful—Extended Mission in Progress
Nation United States
Alternate Names MER 2, MER-A, Mars Exploration Rover A, Mars Exploration Rover 2, 2003-027A


NASA's Mars Exploration Rovers—Opportunity and its twin Spirit—were designed to study the history of climate and water at sites on Mars where conditions may once have been favorable to life. Each rover is equipped with a suite of science instruments to read the geologic record at each site, to investigate what role water played there and to determine how suitable the conditions would have been for life.

A 3D model of the twin Mars Exploration Rovers, Spirit and Opportunity. Credit: NASA Visualization Technology Applications and Development (VTAD) › Download Options


Both rovers far exceeded their design specifications and returned science results that transformed our understanding of Mars.

Spirit, described as a "wonderful workhorse," explored for years beyond its original 92 day mission. The rover revealed an ancient Mars that was very different from the Mars we see today. Spirit uncovered strong evidence that Mars was much wetter than it is now in a silica patch apparently produced by hot springs or steam vents. The rover captured movies of dust devils in motion, leading to a better understanding of Martian wind. Spirit continued to make discoveries even as it was stuck in deep sand at a spot dubbed Troy at Gusev Crater on Mars.

On May 25, 2011, NASA ended efforts to contact the marooned rover and declared its mission complete. The rover had been silent since March 2010.

Key Dates

June 10, 2003 | 17:58:46 UT: Launch
Jan. 4, 2004 | 04:35 UT: Mars Landing

In Depth

Initially known as Mars Exploration Rover A, Spirit, launched to Mars on June 10, 2003 and landed on Mars on Jan. 4, 2004 (UTC). NASA's robot geologist, Spirit, is one of two twin rovers part of the Mars Exploration Rovers mission. Opportunity, Spirit's twin, launched to Mars on 7 July 2003 and arrived on Mars on Jan. 25, 2004 (UTC).

Both Spirit and Opportunity were sent in search of answers about the history of water on Mars. Also, primary among the mission's scientific goals is to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars.

Spirit and Opportunity were targeted to sites on opposite sides of Mars. These sites were chosen because each appears to have been affected by liquid water in the past. Spirit landed in Gusev Crater, a possible former lake in a giant impact crater, and Opportunity landed in Meridiani Planum. Mineral deposits (hematite) in Meridani Planum suggest Mars had a wet past.

After the airbag-protected landing craft settled onto the surface on Jan. 4, 2004 (PST), it opened and Spirit rolled out to take panoramic images of Gusev Crater. These initial images gave scientists the information they needed to select promising geological targets. Spirit then drove to those locations to perform on-site scientific investigations.

The goal for each rover was to drive up to about 44 yards (40 meters (about 44 meters) in a single day, for a total of up to one kilometer (about three-quarters of a mile) during a 92-day mission. Both goals have been far exceeded.

Spirit survived several Martian winters despite low light and low energy for its solar panels. Before becoming mired in deep soil at a spot dubbed Troy (14.6 degrees south, 175.5 degrees east) at Gusev crater on Mars, Spirit had trekked 4.8 miles (7.73 kilometers) across Gusev crater, driving backwards after the left front wheel stopped functioning in 2006. Spirit crossed the Columbia Hills, reaching the 269-foot (82-meters) summit of "Husband Hill," the highest peak in the range. Opportunity, on the other hand has been roving the surface of Mars since 2004.

Spirit sent back more than 127,000 raw images and 16 color, 360-degree panoramic mosaics. It drilled into 15 rock targets and scoured 92 with a special brush. On May 25, 2011, NASA ended efforts to contact the marooned rover and declared its mission complete. The rover had been silent since March 2010.

Spirit's Major Scientific Accomplishments:

  • 2007: Unearthed a patch of nearly pure silica, the main ingredient of window glass, while dragging its right front wheel. The silica patch, dubbed "Gertrude Weise," provided strong evidence that ancient Mars was much wetter than it is now because it was likely produced in an environment of hot springs or steam vents. This is the rover's biggest scientific achievement to date.

  • 2006: Found evidence of a long-ago explosion at a bright, low plateau called "Home Plate." Spirit imaged coarse, bulbous grains overlaying finer material, which fits with the pattern of accumulation of material falling to the ground after a volcanic or impact explosion. These rocks, some of which had never been seen before on Mars, revealed the crater's violent history.

  • 2006: Churned up bright Martian soil at a place named "Tyrone" that contained much sulfur and a trace of water. This material could be a volcanic deposit formed around ancient gas vents or could have been left behind by water that dissolved these minerals underground and evaporated when they came to the surface.

  • 2005: Captured several movies of dust devils in motion, providing the best look of the wind effects on the Martian surface as they were happening.

  • 2004: Discovered a surprising variety of bedrock in Columbia Hills, showing a complex geological history for the region. Some of the rocks showed evidence of alteration by water.

"Spirit has been a wonderful workhorse," Steve Squyres, of Cornell University, Ithaca, N.Y., principal investigator for the Mars rovers' science instruments. "Because of Spirit's visit to the Columbia Hills, we know it was a violent place, a place churned by impacts and volcanic explosions. Spirit has shown us an ancient Mars that was very different from the Mars we see today.

The Mars Exploration Rover mission is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of the red planet.


Launch Vehicle: Delta II 7925

Spacecraft Mass: Total mass at launch was 1,062 kilograms; the rover weighs 174 kilograms

Spacecraft Instruments:

  1. Panoramic cameras

  2. Miniature thermal emission spectrometer

  3. Mossbauer spectrometer

  4. Alpha particle X-ray spectrometer

  5. Microscopic imager

  6. Rock abrasion tool

  7. Magnet arrays

Additional Resources

NASA: Spirit

NASA Mars Program: Spirit

National Space Science Data Center Master Catalog: Spirit

Mars Exploration Program

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