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Past Missions

For nearly 50 years, our civilization has been attempting to send spacecraft to Mars. By the beginning of the 21st century, only 10 missions out of 33 tries had been a complete success. Journey with us down the rocky road of Mars exploration.

Mars Polar Lander/ Deep Space 2: Jan. 3, 1999

Slice into a martian polar cap and you might see alternating bands of color ranging from pristine white to murky orange. These bands are a record of the ice and dust that have been laid down over time. Like growth rings of a tree, the alternating layers may help reveal what environmental conditions were like when they were formed and offer clues to past climates on Mars. The Mars Polar Lander (MPL) was designed to unearth these clues by landing on layered terrain near the planet's south pole.

MPL was scheduled to touch down on the surface of Mars on December 3, 1999. It was to gather images of the icy terrain, as well as probe the polar cap with a suite of five instruments. The science payload was called MVACS, Mars Volatiles and Climate Surveyor. Volatiles are substances that can evaporate easily. At the poles of Mars, carbon dioxide and water are considered volatiles because they change from vapor to ice (or visa versa) in one season. MVACS was to study the surface-to-atmosphere cycle of carbon dioxide and water on Mars by measuring the amounts of these substances in the atmosphere, in the ice, and in the soil.

The MVACS package included a Meteorological Package (MET), which was a weather station; the Surface Stereo Imager (SSI), which would take multi-color images of Mars; the Thermal and Evolved Gas Analyzer (TEGA), which would look for water, carbon dioxide, and water-bearing minerals in the soil; the Robotic Arm (RA), to dig trenches and collect soil samples for TEGA to study; and the Robotic Arm Camera (RAC), to take images of the trenches made by the RA.

The lander also carried a camera that would photograph the surface during descent (the Mars Descent Imager -- MARDI), and a Light Detection and Ranging instrument (LIDAR) built by the Russians to measure dust and haze in the atmosphere. A microphone was aboard to record the sounds of Mars.

Riding piggyback on the Mars Polar Lander was another mission named Deep Space 2. Two "microprobes" were mounted on the MPL's cruise stage for release during descent. The probes were designed to use the force of a hard impact to penetrate up to 2 meters into the south pole of Mars. Each probe consisted of two parts -- a short cylinder that would remain above the surface of Mars for radio communications, and a long, thin cylinder that would plunge underground. The subsurface cylinder included a temperature sensor, a soil sample chamber, and ice and water vapor detection equipment. The goal of the Deep Space 2 mission was to demonstrate the new microprobe technology and its ability to search for water ice beneath the surface of Mars.

None of the instruments in either mission would have a chance to return data.

At about 12 minutes before the Mars Polar Lander was scheduled to land, the spacecraft was healthy and ready to enter the martian atmosphere. The spacecraft turned its antenna away from Earth, as planned, and it was never heard from again. Engineers struggled for weeks to find a radio signal, but without success. MPL's Entry, Descent, and Landing system underwent extensive scrutiny. Much of the system was inherited from the Mars Pathfinder mission, but MPL did not inherit the airbag method of landing. Instead, it was to achieve a pinpoint landing via retro-rockets and legs, much like the Viking landers did 20 years earlier. A press release dated March 28, 2000 states:

"… the most probable cause of the failure (of MPL) was the generation of spurious signals when the lander legs were deployed during descent. The spurious signals gave a false indication that the spacecraft had landed, resulting in a premature shutdown of the engines and the destruction of the lander when it crashed on Mars."

Following the failure of both the Mars Climate Orbiter and the Mars Polar Lander, NASA conducted an in-depth review of its entire Mars exploration program. The next lander mission, which was scheduled for launch in 2001 and carried the Athena Precursor Experiment (APEX), was canceled. Its spacecraft was a near-twin of the Mars Polar Lander. The 2001 launch window would only see an orbiter, Mars Odyssey, begin a journey to the Red Planet.

Mars Climate Orbiter: Dec. 11, 1998

In the three years preceding the launch of the Mars Climate Orbiter, America had successfully lofted several spacecraft into the heavens. Cassini was on its way to Saturn; the NEAR (Near Earth Asteroid Rendezvous) probe was closing in on asteroid Eros; and Deep Space 1 was on target for a flyby of two asteroids and a comet. By 1998, America had found success at Mars as well. The Mars Pathfinder mission had placed a rover on the Red Planet, and the Mars Global Surveyor orbiter would soon begin its mapping operations.

On the heels of these successes came the Mars Surveyor '98 program. It included an orbiter — the Mars Climate Orbiter, and a lander — the Mars Polar Lander. They would launch separately, but both shared the common science goal of studying water on Mars.

Mars Climate Orbiter (MCO) was a weather satellite that was designed to monitor the daily and seasonal weather patterns on Mars. Just like weather satellites in Earth orbit, MCO was to take pictures of martian clouds, look for storms, and monitor winds. It was to gather information about water vapor and dust in the martian atmosphere, explore climate processes that trigger dust storms; and search for evidence of past climate changes.

Two science instruments would do the job. The Mars Color Imager (MARCI) included a wide angle and medium angle CCD camera to gather daily images. From these images, scientists would garner a season-to-season weather portrait of Mars. The other instrument was the Pressure Modulator Infrared Radiometer (PMIRR). It would scan the planet's thin atmosphere to measure temperature, water vapor, and dust. This was a duplicate of the infrared radiometer that flew on the failed Mars Observer mission.

The Mars Climate Orbiter's initial task was to serve as communications relay for the Mars Polar Lander (MPL). The plan was that after MPL's surface operations ended, the orbiter's science mission would begin and continue for one martian year (687 Earth days). The mission's projected completion date was December 1, 2004, but it ended much sooner.

On September 23, 1999, MCO fired its main engine to slow its speed for orbit insertion. Information received from the spacecraft up to that time looked normal. The engine burn happened as planned and the orbiter passed behind Mars. Then the nightmare began. Flight controllers could not find a signal. MCO was not where it was expected to be. A frantic scan of the sky with the Deep Space Network's giant antennas was met with silence.

Failure review teams would later find that the problem was "the failed translation of English units into metric units in a segment of ground-based, navigation-related mission software." This software was critical to placing the spacecraft on the correct path for Mars orbit insertion. The Mars Climate Orbiter should have approached the planet at an altitude of about 150 km (93 miles). But data indicated that the actual approach altitude had been much lower — too low for the spacecraft to survive the stresses and friction in the atmosphere. What was once a robust spacecraft had become a fireball.

Scientists and engineers comforted themselves with the knowledge that Mars Polar Lander would be arriving at Mars in a little more than two months. It was to touch down near the south pole of the planet on December 3, 1999. But Mars was not ready for visitors.

Nozomi: July 4, 1998

By 1998, Japan’s Institute of Space and Astronautical Science (ISAS) and its predecessor, the Institute of Space and Aeronautical Science, had launched several scientific satellites. Nozomi (which means “Hope”) would be the institute’s first probe to another planet and the first spacecraft sent to Mars by a country other than the United States and Russia. It would prove to be a challenging mission.

Nozomi was launched exactly one year after the Mars Pathfinder landing. Its objective is to study the motion and structure of the martian upper atmosphere and how it is affected by the solar wind. Knowledge about the mechanisms of the atmosphere may help scientists solve the mystery of why Mars lost its liquid water. The orbiter was scheduled to arrive at Mars in October of 1999, but the 15-month journey stretched to five years when mission engineers found themselves in a battle to keep the spacecraft alive.

The original plan was for Nozomi to stay in an elliptical orbit around the Earth for four months after launch, use two swing-bys of the Moon in 1998 to tweak its elliptical path, and then pass by the Earth in December of that year for a gravitational boost into a trajectory for Mars. But a thruster malfunctioned and the boost was not enough. Propellant had to be used to keep Nozomi on target. These unscheduled course corrections left the lightweight spacecraft short on fuel – fuel that would be needed at the other end of the trip to enter an orbit around Mars.

Mission engineers crafted a new trajectory. The plan called for Nozomi to stay in an orbit around the sun for four more years. There would be two more Earth flybys in December 2002 and June 2003. However, as Nozomi orbited the Sun, the spacecraft was bombarded with a powerful solar flare in April of 2002. The burst of radiation damaged communications and power systems. Mission engineers struggled to regain control of the spacecraft and were able to salvage the Earth flyby in December of that year.

The June 2003 swingby of the Earth will insert Nozomi into the proper orbit for its journey to Mars. Arrival at Mars will be sometime between mid-December 2003 and early January, 2004. The exact date depends on the extent of the orbital correction maneuvers that have to be performed following the final Earth flyby.

When Nozomi finally reaches the Red Planet, its 14 science instruments will gather data about the martian atmosphere and ionosphere; search for a magnetic field and take precise measurements of its strength; anlayze how dust storms are generated; monitor changes in the polar ice caps; take images of martian weather, as well as the moons Phobos and Deimos; and search for a dust ring along the orbit of Phobos. The international mission includes a spectrometer from Sweden, a plasma analyzer from Canada, a dust counter from Germany, a camera developed in collaboration with France, and a spectrometer and radio science hardware from the United States.

The Nozomi mission was designed to last for at least two years (one martian year). Fuel will be the critical factor. The length of time the orbiter will operate depends on the amount of fuel that is consumed when it is maneuvered into an orbit around Mars.

Mars Pathfinder: Dec. 4, 1996

The greatest danger to the Mars Pathfinder mission was not the hazard of a rocket launch, space travel, or operations in a hostile planetary environment, but rather the threat of being canceled before it ever got off the ground. Work on Pathfinder began in 1992. By 1995, its reviewers saw the mission as too risky and many experts said it would never work. These critics began to take steps to cancel the mission. But the Pathfinder team demonstrated that it was able to meet each challenge and created one of the most successful technology missions ever sent to Mars.

Pathfinder was designed to be an engineering mission to demonstrate new spacecraft technologies that could take America back to the surface of Mars for dramatically less than the cost of the Viking missions. However, Pathfinder’s critics were quick to point out that the mission’s technical problems seemed overwhelming. Viking was 20 years in the past. Many of the people who knew how to put a lander on Mars had retired. Mars Observer would have provided helpful data, but its demise left Pathfinder engineers combing through old Viking records for information on expected surface and atmospheric conditions. Time and fate made the situation difficult, especially since the Pathfinder team was operating under NASA's new Discovery Program dictate of "faster, better, cheaper." They had to make their mission work at one-fifth the cost of Viking.

One of the major problems faced by Pathfinder engineers was to develop an entry, descent, and landing (EDL) system that was cheaper than that used by Viking, but still reliable. An idea was borrowed from Soviet landers. They had used airbags to cushion landings on the Moon and Venus. This eliminated the need for the extensive use of costly fuel to control braking rockets for a pinpoint landing. Following this lead, Pathfinder’s tetrahedral lander was wrapped in a cluster of resilient airbags. The new EDL system was not an immediate success, however. When dropped on a platform of jagged, Mars-like rocks, initial impacts left the airbags with gaping holes. The fabric was reinforced and the design was tweaked until future tests proved successful.

An additional technology and science component of the Pathfinder mission was the inclusion of a small rover. The Sojourner Rover would be the first rover to put its wheels in martian soil. But its addition to the mission created several more problems for the Pathfinder team. How would the rover be able to get around a rocky martian landscape without getting stuck? Where should Pathfinder land to allow the rover to drive safely and make the best use of its science potential? And how could something the size of a microwave oven do any real science?

Engineers went to work designing a new mobility system that put the rover’s wheels on levers. This “rocker-bogie” suspension allowed Sojourner to move up and down over rough terrain without tipping over. This capability was also critical to the rover’s power supply. The solar panels on top of Sojourner had to be kept level to receive the most sunlight.

To save fuel and money, Pathfinder would not orbit Mars before it landed, but rather would make a direct entry into the martian atmosphere. Unlike Viking, Pathfinder engineers would not have the luxury of changing their minds about a landing site after launch. The decision would have to be final. The process of finding an appropriate landing site to satisfy landing safety and scientific interest took more than two years. One of Pathfinder's science goals was to study a variety of rocks. But too many rocks pose a landing hazard for the airbags. Ultimately, an outflow channel in a location called Chryse Planitia, not far from the Viking 1 landing site, was chosen. Named Ares Vallis, it appeared to be the site of a catastrophic flood on Mars -- good for a geologic mission, but critics worried that the region had too many rocks to be safe for an airbag landing.

The Sojourner Rover may have been small, but it carried out some significant science investigations. It was equipped with three cameras and an Alpha-Proton-X-Ray Spectrometer (APXS) to analyze martian rocks. The rover communicated its findings to Earth through the lander, which also carried its own science instruments. The Pathfinder lander had a stereo camera, a weather station with pressure, temperature, and wind speed instruments, and magnets to study the properties of dust in the martian atmosphere.

Mars Pathfinder launched on Dec. 4, 1996 after two delays due to weather and computer problems. It landed safely on Mars on July 4, 1997. The airbags survived the landing, bouncing more than 16 times and as high as 15 meters (50 feet) on initial contact with the martian surface. The lander, formally named the Carl Sagan Memorial Station after touchdown, returned spectacular images of Mars. Sojourner was commanded to leave the lander on the second day of the mission. The small rover used its APXS to make chemical analyses of nearby rocks and used its cameras to image the rocks and soils up close. The public became enraptured with the "little rover that could."

The Pathfinder mission was designed to last one month, but the lander and rover actually operated for 83 Mars days, or Sols. During that time, a wealth of images and other data were returned to Earth. There was information from the lander’s weather station that revealed rapid pressure and temperature variations on Mars; evidence that martian dust includes magnetic, composite particles; evidence of dune-shaped deposits which indicate the presence of sand on Mars; a distribution of rocks that appeared to be caused by flooding; and the possible identification of rounded pebbles that could have been formed in running water on a warmer and wetter Mars.

Credit: NASA/JPL
A Pathfinder panorama of Mars taken at sunset.

Pathfinder had done its job well. A mission that was nearly canceled had become an enormous success and captured the world's attention. Most importantly, Pathfinder demonstrated some key technologies and operations procedures that could be used for future missions. Plans were put into motion for another rover to visit the surface of the Red Planet. These plans would later give rise to the Mars Exploration Rover mission.

Mars 96: Nov. 16, 1996

Dramatic changes had occurred in Russia since the time of the Phobos missions in the late 1980s. The old Soviet Union was dissolved, and the republics that had formed the USSR became independent nations. Russia took over the Soviet space program, and struggled to keep it going during difficult economic times. The Buran, a twin to America's Space Shuttle, was scrapped in 1993. As the cold war faded, the United States and Russia began to work together in space. Cosmonauts rode the American space shuttle, and astronauts worked on the Russian Mir space station. Still, money for Russian planetary missions was very tight. A new mission to Mars that was to launch in 1994 had to be postponed. The result was a very ambitious project called Mars 96.

The goal of the Mars 96 mission was to perform extensive studies of the atmosphere, surface and interior of Mars. The spacecraft was created using experience and knowledge gained from Russia's successful missions to Venus and failed missions to Mars. It carried an orbiter based on the Phobos design with more than 20 science instruments. It also carried two small landers packed with additional science equipment, and two surface penetrators with several sensors.

The Mars 96 landers were designed to separate from the main spacecraft and fly on their own to selected landing sites. They were to survive an entire martian year (687 Earth days) so that science instruments could gather information about seasonal changes in the atmosphere, study martian soils, measure magnetic fields, and record any seismic activity. Each lander also carried a panoramic camera to view the nearby landscape.

The two surface penetrators were also designed to last one martian year. Impact with the surface would drive the tip of each probe deep into the soil. One section of the penetrator would remain on the surface, but stay connected by wires to the deeper probe. Instruments were located in both sections of the device. They included a television camera, spectrometers, seismometers and a neutron detector.

Mars 96 was scheduled to reach the Red Planet on Sept. 12, 1997, but it never left Earth orbit. A failure during the second ignition of the Proton rocket's upper stage sent the spacecraft tumbling into the Pacific Ocean. A review board was convened, but was unable to determine the exact cause of the failure. To date, there have been no more Russian missions to Mars.

Mars Global Surveyor: Nov. 7, 1996

From the ashes of the failed Mars Observer mission came an orbiter that would find extreme success. It was designed with knowledge gleaned from Observer's failure reports and built using many spare parts from that mission. It was also tailored to fit cost-cutting measures that became mandatory during NASA's new era of "faster, better, cheaper." The result was a robust spacecraft far less expensive than its predecessor. The Mars Global Surveyor (MGS) has not only surpassed its goals, it has returned a wealth of information about Mars, and continues to examine the Red Planet today.

However, the mission was not without its problems. Shortly after launch, one of the orbiter's two solar panels did not deploy properly. It unfolded, but did not lock because of debris lodged in a hinge. The problem would later haunt engineers.

As MGS approached the point where the Mars Observer had been lost, tensions ran high. There was a collective sigh of relief when engines fired successfully. The craft went into a highly elliptical orbit around Mars to begin its aerobraking phase. Aerobraking is a method of slowing the spacecraft by dipping into the Martian atmosphere and using solar arrays to create drag. Like a mainsail taut with wind, aerobraking places a strain on the solar arrays. The jammed solar panel resurfaced as a concern. Would the maneuver cause it to snap off? Engineers resorted to a gentler method of aerobraking which meant that MGS would take at least a year longer to arrive at its nearly-circular orbit around Mars. Mapping the planet did not begin until March of 1999, but would continue far longer than the anticipated January, 2001 end date.

The objectives of the Mars Global Surveyor mission were similar to that of the Mars Observer -- conduct an extensive two-year study of Mars to gather detailed measurements of its surface and atmosphere. Most of the instruments MGS carries are flight spares from the Observer mission. They are a magnetometer and electron reflectometer to study the planet's magnetic field; a camera to image the surface; a laser altimeter to map the height of surface features; thermal emission spectrometer to investigate surface and atmospheric properties by measuring radiated heat; and an oscillator for radio science to study the Martian gravity field and track atmospheric pressure and temperature.

The orbiter is also equipped with a relay system so that information from spacecraft on the surface of Mars can be relayed to Earth. Anticipating that MGS still will be functioning in 2004, its relay system will be used to transmit information gathered by the Mars Exploration Rovers.

The Mars Global Surveyor has returned more information about the surface, atmosphere and interior of Mars than all other Mars missions combined. MGS achievements include a detailed global topographic map of Mars; global models of the Martian crust; evidence that Mars once had a magnetic field which is lacking today; the discovery of hematite deposits; information about the role of wind and dust in the Martian climate; and possible evidence for recent liquid water on Mars. The Mars Orbiter Camera continues to capture spectacular views of the surface of Mars, adding to an archive of more than 100,000 images.

Currently, MGS in its third extended mission and is aiding in the selection of landing sites for the Mars rovers. Its daily activities also include monitoring Martian storms and weather patterns, searching for changes in surface features, and observing new areas of interest to science.

Mars Observer: Sept. 25, 1992

Seventeen years had passed since America sent a spacecraft to Mars. It was an expanse of time that saw the Soviet Union continue to explore Venus, the United States send probes of its own to that planet, Voyager 1 and 2 journey to the gas giants, the Space Shuttle come into being, European and Japanese probes study Halley's Comet, the rise of Russia's Mir Space Station, the Galileo spacecraft travel to Jupiter, and the launch of the Hubble Space Telescope. America was ready to return to Mars.

Mars Observer was a massive orbiter that was similar to Earth-orbiting satellites of its day. It was designed to remotely probe the Red Planet's surface, atmosphere, and interior in fine detail over the course of one Martian year (687 Earth days). Equipment on the rectangular bus included computers, a radio system, tape recorders, and fuel tanks. Four of seven science instruments were mounted on a panel that would always face the planet. They were a camera to image the entire surface of Mars, a laser altimeter to create topographic maps, an infrared radiometer to monitor the atmosphere, and a thermal emission spectrometer to determine the properties of rocks and soils. Two other instruments were located on booms so their readings would not be affected by emissions from the spacecraft. They were the magnetometer/electron reflectometer to search for magnetic fields, and the gamma-ray spectrometer to identify chemical elements. Mars Observer's radio system was considered to be a seventh instrument. Scientists planned to use it to map the Martian gravity field.

The journey to Mars took 11 months and, during that time, there was no hint of the tragic events to come that would doom the mission. On August 21, 1993, only three days before the spacecraft was scheduled for orbit insertion, Mars Observer fell silent. It happened just as a command was executed that should have pressurized the propulsion system that was to slow the spacecraft as it approached the planet. Engineers sent backup commands and made frantic efforts to find a signal, but contact was never reestablished. Mars had refused visitors once again.

In the months that followed, an investigation board tried to piece together the very little information they had in order to find a reason for the loss. It finally concluded that ruptured tubing in the propulsion system caused Mars Observer to spin out of control. A liquid-propellant rocket mixes fuel and an oxidizer in a combustion chamber to get the high-pressure stream of gases needed to propel or slow a spacecraft. The board surmised that, during the long, cold journey to Mars, nitrogen tetroxide (an oxidizer) had seeped into and condensed in the fuel lines. When the fuel hit the liquid oxidizer, the resulting combustion caused a rupture in the tubing instead of in the combustion chamber. The board's findings included remarks that there had been too much reliance on a design taken from Earth orbiting satellites. Even though the orbiter had been modified for Mars, the long duration cold soak of interplanetary travel is very different from a low Earth orbit. Still, the board was careful to state that there could be no exact determination for the failure of Mars Observer.

The demise of the Mars Observer spacecraft triggered a restructuring of NASA's entire Mars program. Too many expensive instruments had flown on one spacecraft. "Faster, better, cheaper" became NASA's catchphrase for the next phase of Mars exploration.

Web content editor/writer: Pamela R. Smith