With four robotic spacecraft in orbit and two Geologist rovers on opposite sides of the planet's surface, it's a challenge to sort out the current Mars missions.
With four robotic spacecraft in orbit, each with seemingly overlapping missions, and two Geologist rovers on opposite sides of the planet's surface, it is difficult these days to sort out the current state of Mars exploration. All six of these remarkable machines arrived at Mars within the past ten years. Each are equipped with an array of unique instruments used to meet the goals of their individual missions. With the exception of the newest arrival, whose mission has just begun, all have far exceeded their original planned lifespans and are still doing great science.
Mars Global Surveyor
The Mars Global Surveyor was launched in November, 1996, atop a Delta II rocket at Cape Canaveral, Florida. It arrived at Mars in September, 1997, the first spacecraft to successfully enter Mars orbit intact and operational in twenty-one years. The Global Surveyor's core mission was to map the Martian surface, atmosphere and interior. It was to perform its science duties over the course of nearly two years, the equivalent of one Martian year. The Global Surveyor found the first clear evidence that in Mars' early history it had a thicker atmosphere and water systems on or near the surface of the planet. Ten years later, the spacecraft is still functioning and it continues to make significant contributions to the study of Mars.
2001 Mars Odyssey
In October, 2001, a second spacecraft entered orbit around Mars. The mission of the 2001 Mars Odyssey was to map the chemical makeup and mineral composition of the planet's surface. Specific mission objectives included determining the extent of ice deposits in the shallow subsurface, mapping the elemental makeup of the entire surface of Mars, capturing high-resolution thermal infrared images of surface minerals, learning more about the structure of the surface, and recording low-orbit radiation levels for human exploration risk assessment. To date, the Odyssey has collected over 130,000 images, enabling scientists to identify regions of subsurface ice, extensively plot the planet's chemical elements and minerals, and create detailed topographical maps. It discovered that the radiation in low-Mars orbit is twice that of Earth's, information that will help prepare for future manned missions. Having far extended its original mission timeline, the 2001 Mars Odyssey is still flying strong, providing support to the surface rovers by relaying data back to Earth. It has also helped to discover possible landing sites for the Phoenix Scout Mission, a new rover heading to Mars later this year.
Mars Express
NASA joined forces with in the European Space Agency and the Italian Space Agency on the Mars Express Mission. It launched aboard a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan in June, 2003. It arrived in orbit of Mars in December of the same year, its main objective to continue the search for subsurface water. Other mission goals included mapping the planet's geology and mineral make-up and perhaps most exciting, deploy the Beagle 2, a geochemistry and exobiology lander, to the surface. Notably, the Beagle 2 was the creation of the European Space Agency and the Mars Express mission was Europe's long-awaited first trip to Mars.
The Beagle 2 lander was a very exciting opportunity for Europe to contribute to the search for life on Mars. It was to take panoramic and wide-field photos and use a microscope to analyze soil and rock fragments within reach of the lander's small robotic arm. The microscopic analysis would focus on looking for signs of organic matter, water and mineral deposits. The Beagle 2 was not itself mobile, but carried with it a companion affectionately known as the mole. This robot could deploy from the lander, slowly crawl short distances and burrow beneath boulders to obtain soil samples for gas analysis. The goal of this experiment was to search for evidence of past organic processes.
Tragically, the Beagle 2 was lost. It ejected from its mothership as planned on December 19, with all systems checking out perfectly. Battery charge level was verified at over 97%. Memory checks confirmed software readiness and data integrity. The entry, decent and landing parameters all checked out as expected. The Beagle 2 never signaled the Mars Express at the anticipated landing time, six days later. No conclusive answers were forthcoming due to lack of data. Perhaps someday high-resolution photographs of the landing area will finally reveal the fate of the lander.
Faring much better than its smaller companion, the Mars Express mission has been a tremendous success. The original mission end date of November, 2005 has been extended twice, now marked for May, 2009. The spacecraft has identified water in the South Polar Cap, has conducted studies of atmospheric composition and circulation and has provided stunning high-resolution photographs of the planet surface. The Italian Space Agency contribution to the mission, the Mars Advanced Radar for Subsurface and Ionospheric Sounding, or MARSIS, has yielded information about underground ice, layered deposits and buried impact craters.
Mars Exploration Rovers
Two years after the Mars Express began it's science mission in orbit of Mars, the 2003 Mars Exploration Rovers Mission was launched by three-stage Delta II rockets from Cape Canaveral. The mission of the two robotic geologists was to perform fieldwork on rocks and soil around their landing areas in an effort to discover a possible history of past water activity on Mars. The rover “Spirit” was launched on June 10, 2003 and it's twin “Opportunity” followed less than a month later in a separate launch. They both made successful landings on Mars in January, 2004. Spirit landed at Gusev Crater, an impact crater that was suspected to have one time held a large lake, as evidenced by the 900 kilometer valley that cuts the crater's edge. Opportunity, landing on the opposite side of the planet, was slated to explore Meridiani Planum, a very smooth and flat area, of interest for it's unusual deposits of hematite detected by the Mars Global Surveyor. On Earth, hematite is often formed in association with water.
The rover's activities on the surface have been dramatically covered in detail on the Internet. Daily mission updates of the rover's positions and experiments, including many compelling photographs, have captured the hearts of the public and done much to re-energize interest in the space program. Spirit found no hard evidence of water erosion at Gusev and it is now thought that the geological features were perhaps caused primarily by impact events and wind erosion. If there is evidence of a lake in the past, it is buried far below the reach of the rover. At Meridiani Planum, Opportunity has discovered evidence of past water events in cross-bedded sediments, small spherical pebbles that are likely concretions, vugs (cavities inside rocks formed by erosion of crystal formations), and large amounts of sulfate-rich minerals.
To the delight of scientists and other followers of the mission, the rovers have far surpassed their original operational goals of 90 days and 600 meters traveled. To date, Spirit has roamed approximately 7000 meters, albeit now on five working wheels instead of six, and has passed it's one thousandth Martian day. Opportunity has traveled over 10,000 meters three years and like its counterpart continues to explore and perform good science. These two now-famous robots have exceeded the best expectations of their designers and represent a huge accomplishment in the annals of space exploration.
Mars Reconnaissance Orbiter
Atop an Atlas V rocket, the latest of NASA's Mars explorers, the Mars Reconnaissance Orbiter lifted off from Cape Canaveral in August, 2005. It arrived in orbit of Mars in March the next year. After months of aerobraking, a technique of controlled dips into the upper atmosphere to make its orbit close to circular, it began its science mission in November. The Reconnaissance Orbiter is charged with scouting out water-related formations that will make excellent choices for future exploration sites. Armed with a high-resolution camera that can capture images as small as one meter across, the orbiter will photograph the surface of Mars in unprecedented detail. During its mission it will also study the atmosphere and weather, examine the polar ice caps to map their internal structure and search for subsurface water and ice. Ongoing, the Mars Reconnaissance Orbiter will provide a communications link between surface craft and scientists on Earth. To date, the orbiter has been in full operation for over three months and has taken incredibly exciting photos of Mars, some of which show strong indications of water processes.
Mars is the place to be today for robotic explorers. More attention and resources have been given to this planet than any other and much has been learned about it in the past decade. A new rover, the Phoenix, will launch in August this year and will continue the pursuit of water on Mars by focusing its mission in the icy northern pole of the planet. Each mission in the past decade has contributed both to the body of knowledge about the red planet, as well as helped to define and focus the objectives of subsequent missions. With six explorers currently studying Mars, it is a very exciting time in the history of the exploration of the fourth planet from the sun.
