Launch Date July 6, 2003 | 03:18:15 UT
Launch Site Cape Canaveral, Florida, USA
Destination Mars
Type Rover
Status Successful—Extended Mission in Progress
Nation United States
Alternate Names MER-B, MER 1, Mars Exploration Rover 1, Mars Exploration Rover B, 27849, 2003-032A


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.


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

Opportunity, the second rover to land on Mars has returned dramatic evidence that its area of Mars stayed wet for an extended period of time long ago, with conditions that could have been suitable for sustaining microbial life. Scientists believe that Opportunity's Meridiani Planum landing site "was once the shoreline of a salty sea on Mars." Opportunity also has analyzed exposed rock layers recording how environmental conditions changed over time. In JUly 2014, Opportunity set the off-Earth roving distance record after accruing 25 miles (40 kilometers) of driving. The previous record was held by the Soviet Union's Lunokhod 2 rover.

Key Dates

July 6, 2003 | 03:18:15 UT: Launch

Jan. 25, 2004: Mars Landing


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: Opportunity

NASA Mars Program: Opportunity

National Space Science Data Center Master Catalog: Opportunity

Mars Exploration Program

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