Space Today Online - Exploring the Red Planet - Past Mars Probes
Exploring the Red Planet
A timeline of past explorations:
Many Robots From Earth Have Probed Mars
1960s     1970s     1980s     1990s     2000s     New Era     Table of Flights     Future Probes
The United States and Russia have spent billions over four decades trying to land a spacecraft on Mars. Many probes have been sent.
On December 2, 1971, the Soviet Union's Mars 3 was the first spacecraft to make a successful soft landing on Mars.
MORE ABOUT MARS 3  »
Later, three American spacecraft completed highly successful landings on the surface — the pair of Viking landers in 1976 and Mars Pathfinder 21 years later in 1997.
In addition, several spacecraft have either flown by the Red Planet, sending back picture postcards as they traveled on, or they have dropped successfully into orbit around Mars.
Numerous other spacecraft over the years either failed to leave Earth at all or were unable to find their way correctly to the Red Planet.
Now, five new craft from America, Europe and Japan are prepared to visit Mars in 2004. If all work as planned, two will remain in orbit around the planet while three landers touch down. The flotilla includes Europe's and Japan's first solo missions to Mars.
The 1960s
By 1960, human space engineers were ready to build and send interplanetary science probes away from Earth toward the Moon and planets. Since then, some two dozen unmanned Mars explorers have been fired into interplanetary space from the U.S. and the USSR to look at the Red Planet and its moons Phobos and Deimos.
The USSR's Mars 1, launched in November 1962, was the first attempt to probe Mars. Unfortunately, contact was lost with the spacecraft only 60 million miles along its route to the Red Planet.
America's Mariner 4 launched in November 1964 was the first successful probe to reach Mars, sending back 22 photos as it flew by in July 1965. The first close-up pictures ever of another world showed a barren wilderness.
Meanwhile, a Soviet probe intended for Mars missed the 1965 window of opportunity for a launch, but was fired off anyway. It faxed back to Earth photographs of the far side of the Moon as it flew away into an orbit around the Sun.
In 1969, the U.S. probes Mariner 6 and Mariner 7 successfully completed the first dual-spacecraft mission to the Red Planet, sending back more than 100 pictures and data on the atmosphere and surface.
Meanwhile, the Soviet Union lost two Mars probes during their launches.
The 1970s
In 1971, the U.S. suffered a loss when the probe Mariner 8 splashed into the ocean off Puerto Rico during launch.
But then the first man-made satellite to orbit a planet other than Earth was America's Mariner 9 which brought us the first close-ups of the Martian moons Phobos and Deimos. Launched toward Mars in May 1971, Mariner 9 arrived in a 12-hour orbit around the Red Planet in that November. Mariner 9 had two TV cameras which sent back 7,329 photos including close-ups of giant volcanoes, canyons and ancient riverbeds.
The Soviet Union in 1971 finally achieved success with Mars 2 and Mars 3, which transmitted data on the harsh atmosphere. The lander from Mars 2 crashed on the surface while the lander from Mars 3 became the first to make a successful soft landing on Mars. However, shortly after the Mars 3 lander touched down on December 2, 1971, it stopped communicating.
Mars 2 and Mars 3 were identical spacecraft – each an orbiter with attached descent module. They were supposed to send back images of the surface along with information about weather conditions, the composition of the atmosphere, and chemical and mechanical properties of the soil. Each had two television cameras, a mass spectrometer to study the atmosphere, and temperature, pressure, and wind sensors. Each had a mechanical scoop to search for organic signs of life.
Both Mars 2 and Mars 3 arrived in orbit over the Red Planet and dropped their descent modules, which were decorated with USSR flags. The descent modules had radar altimeters, cone-shaped aerodynamic braking shields, parachutes and retro-rockets. After landing, four triangular petals would open, turning the spacecraft upright and exposing the science instruments.
Each lander carried a small maneuverable robot called PROP-M. Each lander would use a manipulator arm to place its rover on the surface in the field of view of its television cameras. Each rover could slide along on a pair of skis, traveling up to 50 feet, while remaining attached to the lander by a tether cable. Each rover had a penetrometer and a radiation densitometer and would stop for measurements every five feet. Movements in the Martian soil would be recorded.
While Mars 2 crashed, Mars 3 made the first soft landing on Mars. After its descent module was separated from the orbiter, its descent engine fired. A braking parachute was deployed. Later, the main parachute popped out, the heat shield was ejected, and the radar altimeter was turned on. When the package was about 75-100 feet above the surface, the main parachute was cut loose and the retrorockets were fired. The entire entry and landing took about three minutes. It hit the ground at about 50 mph with its built-in shock absorbers preventing damage to the instruments.
The four petals covering the Mars 3 lander opened and, 90 seconds later, the capsule began transmitting to the Mars 3 orbiter. Unfortunately, the transmission stopped after only 20 seconds and no further signals were received. It wasn't possible to tell what failed – the lander or the orbiter's communications relay. One partial panoramic image was relayed to Earth, but it was dark with no detail. Could the dark picture have been caused by a powerful dust storm taking place around the landing site at the time?
The USSR tried to send four probes to Mars in 1973-74. Mars 4 and Mars 5 were intended for orbit around the planet. Mars 5 succeeded. Mars 6 was to land on Mars, but crashed. Mars 7 missed the planet.
Viking 1 and Viking 2 carried the American flag across millions of miles of interplanetary space to photograph Mars, Phobos and Deimos, and land on the Red Planet  in 1976. The Vikings have been the most scientifically-profitable Martian operations to date.
Viking 1 launched September 9, 1975, arrived at Mars June 19, 1976, and landed.
Viking 2 launched August 20, 1975, arrived at Mars August 7, 1976, and landed.
Viking bio-tests turned up unusual chemical activity in the soil, but any finding of evidence of life remains controversial even today. At the time, the planet was said to be sterile.
The 1980s
In 1988, the Soviet Union sent two probes to Mars. They were designed to explore the Sun while enroute, and then Mars and the Martian moon Phobos — the spacecraft were named Phobos 1 and Phobos 2.
A software glitch led to loss of contact with Phobos 1.
Phobos 2 carried the USSR flag 111 million miles to Mars orbit on January 29, 1989. It detected water vapor in the Martian atmosphere and sent back some photos. However, a computer problem ended the its mission before the spacecraft could send a robot probe to land on the moon Phobos.
The 1990s
In 1993, after a Mars-launch hiatus of 18 years, the U.S. sent a new spacecraft — Mars Observer — to look in on the Red Planet. Unfortunately, it's signal was lost three days before it was to fly into orbit around Mars.
In 1996, America launched Mars Global Surveyor to map the Red Planet. MGS sent home more than 120,000 pictures along with data raising a possibility of water beneath the martian surface.
Meanwhile, Russia tried to send its Mars 96 probe, but the spacecraft splashed into the Pacific Ocean at launch.
The next year, America's Pathfinder landed on Mars. Millions of people on Earth watched as the lander sent out a rover named Sojourner for a close-up look at rocks and the terrain. Pathfinder sent back more than 20,000 images that made it seem Mars once might have been warm and wet.
Japan launched its Planet-B interplanetary probe on July 3, 1998, to look for signs of water on Mars and measure the Red Planet's magnetic field. In space, it was renamed Nozomi, which is Japanese for Hope. The spacecraft was Japan's first interplanetary mission. Previously, only the United States and Russia had sent spacecraft to Mars.
MORE ABOUT NOZOMI  »
The U.S. suffered two setbacks from 1999 launches. Its Climate Orbiter was lost as it arrived at Mars. Then the signal from Polar Lander was lost when it was supposed to touch down near the south pole of the Red Planet.
The 2000s
In 2001, the U.S. probe Mars Odyssey was sent to examine the composition of the Martian surface, to look for water and ice, and to study the radiation environment. In the process, it created the first large-scale geological map of the planet.
MORE ABOUT MARS EXPLORATION ROVERS  »
Meanwhile, the first Japanese Mars orbiter, Planet B or Nozomi, continues on its 4.5 year voyage from Earth to the Red Planet.
The five craft – Mars Express with Beagle 2, Nozomi, and the twin Mars Exploration Rovers – will arrive in December 2003 and January 2004.
The New Era
A new era of sophisticated robot interplanetary probes that may be launched from Earth by the United States, Europe, Japan, Russia and China in the 21st century will continue to teach us many new things about Mars and help us solve some old mysteries of the Solar System.