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Mars Exploration Rovers

National Aeronautics and Space Administration


Both rovers are in extended mission operations on the surface of Mars.


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

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. The spacecraft were targeted to sites on opposite sides of Mars that appear to have been affected by liquid water in the past. The landing sites are at Gusev Crater, a possible former lake in a giant impact crater, and Meridiani Planum, where mineral deposits (hematite) suggest Mars had a wet past.


Launch of first rover, Spirit: June 10, 2003
Spirit's arrival on Mars: Jan. 3, 2004

Launch of second rover, Opportunity: July 7, 2003
Opportunity's arrival on Mars: January 24, 2004

Two powerful new Mars rovers are on the red planet. With far greater mobility than the 1997 Mars Pathfinder rover, these robotic explorers may trek as much as 40 meters (44 yards) across the surface in a day. Each rover carries a sophisticated set of instruments to search for evidence of liquid water that may have been present in the planet's past.

The landing for each rover resembled that of the Pathfinder mission. A parachute deployed to slow the spacecraft, rockets fired to slow it further just before impact, and airbags inflated to cushion the landing. Upon reaching the surface, the spacecraft bounced about a dozen times. When it stopped, the airbags deflated and retracted and the petals opened up, bringing the lander to an upright position and revealing the rover.

The landed portion of the mission features a design dramatically different from Mars Pathfinder. Where Pathfinder had scientific instruments on both the lander and the small Sojourner rover, these larger rovers will carry all their instruments with them. Immediately after landing, each rover began reconnaissance of the landing site by taking a 360-degree visible color and infrared image panorama. Then each, leaving the petal structure behind, drove off to begin exploration.

Using images and spectra taken daily from the rovers, scientists command the vehicle to go to rock and soil targets of interest and evaluate their composition and their texture at microscopic scales. Initial targets were close to the landing sites, but later targets are now far afield. These rovers are able to travel almost as far in one Martian day as the Sojourner rover did over its entire lifetime.

Rocks and soils are analyzed with a set of five instruments on each rover, and a special device called the rock abrasion tool is used to expose fresh rock surfaces for study. Each rover has a mass of nearly 180 kilograms (about 400 pounds). The prime mission for each rover will last three months on the surface.

Primary Science Instruments

* Panoramic Camera (PanCam): for determining the mineralogy, texture, and structure of the local terrain.

* Miniature Thermal Emission Spectrometer (Mini-TES): for identifying promising rocks and soils for closer examination and for determining the processes that formed Martian rocks. The instrument will also look skyward to provide temperature profiles of the Martian atmosphere.

* Mössbauer Spectrometer (MB): for close-up investigations of the mineralogy of iron-bearing rocks and soils.

* Alpha Particle X-Ray Spectrometer (APXS): for close-up analysis of the abundances of elements that make up rocks and soils.

* Magnets: for collecting magnetic dust particles. The Mössbauer Spectrometer and the Alpha Particle X-ray Spectrometer will analyze the particles collected and help determine the ratio of magnetic particles to non-magnetic particles. They will also analyze the composition of magnetic minerals in airborne dust and rocks that have been ground by the Rock Abrasion Tool.

* Microscopic Imager (MI): for obtaining close-up, high-resolution images of rocks and soils.

* Rock Abrasion Tool (RAT): for removing dusty and weathered rock surfaces and exposing fresh material for examination by instruments onboard.

Extended Mission

As of September 21, 2004 NASA extended funding for an additional six months of rover operations, as long as they keep working. Both rovers successfully completed their primary three-month missions on the surface of Mars in April and have already added about five months of bonus exploration during the first extension of their missions.

Rover science team members will spend less time at JPL during the second mission extension. They are able to attend daily planning meetings by teleconferencing from their home institutions in several states and in Europe. Workstations researchers used at JPL are at their home institutions. Planning tools include video feeds, workstation display remote viewing, and audio conferencing. Besides reducing costs, remote operations allow scientists to spend more time at home.

Another change in operations is a shift from seven days per week to five days per week from October through December. This accommodates a temporary trim of about 20 percent in the project's engineering team to about 100 members. The rovers' reduced energy supply, during the rest of the martian winter, makes the inactive days valuable for recharging batteries. By January, the energy situation will have improved for the solar-powered rovers, provided they are still operating. The team size will rebound to support daily operations.

Spirit  UPDATE: sol 305, November 18, 2004
Spirit remains in excellent health and has survived more than 300 martian days on the red planet.For coming sols, Spirit is in an exploration and discovery mode, continuing the rover's ascent towards "Machu Picchu" in the Columbia Hills. Spirit will stop at interesting rocks along the way.

Opportunity  UPDATE: sol 291, November 23, 2004
Opportunity has now reached the furthest point east in its travels inside "Endurance Crater." Rover drivers have determined that there is no safe path beyond the current position. Therefore, Opportunity is now in the midst of an intensive remote-sensing campaign, capturing a panorama of Burns Cliff plus super-resolution images and miniature thermal emission spectrometer observations of selected targets. When this campaign concludes, the rover will back away and head for a way out of Endurance Crater. Opportunity remains healthy and in an extremely advantageous solar array attitude.

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