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Farewell To Mars Pathfinder —
Mission Accomplished!

Artist's conception of Pathfinder on Mars

On September 27, 1997, mission controllers at NASA/JPL in Pasadena, California, finally lost contact with the Mars Pathfinder lander on the surface of the Red Planet. Pathinder had been designed to work for about one month, but in the end it sent back a rich stream of pictures and other data for almost three months. Engineers suspect that contact was lost because the spacecraft was literally frozen into silence. The extreme cold temperatures on Mars (a low of -107 degrees F, or -77 degrees C) may have broken something in the electronic circuitry — perhaps simply a cracked solder joint. Attempts will be made from time to time to re-establish contact with Pathfinder, but even if that fails, the overall mission must be regarded as a stunning scientific and engineering success.

In its 83 Martian days on the surface of the planet, the Pathfinder lander (renamed the Carl Sagan Memorial Station, in tribute to the late astronomer) and its mobile robot sidekick, named Sojourner, observed their surroundings at the mouth of Ares Vallis, an ancient dry river channel. The panoramic images and other data sent back to Earth showed that Mars has a wide variety of rock types, and provided additional evidence that the surface of the planet was once sculpted by erosion from flowing water.

The Landing

On July 4, after slicing through the Red Planet's thin atmosphere at an entry speed of 27,000 kilometers per hour (about 17,000 miles per hour), Pathfinder touched down on the desolate plain at the mouth of Mars Valley (Ares Vallis) in Chryse Planitia (Plain of Gold) shortly before sunrise, ending a seven-month journey from Cape Canaveral, Florida, planet Earth. The first Mars landing in over 20 years, Pathfinder opened a new chapter in planetary exploration.

The Brains of the Operation

A few hours before dawn on Mars, the Pathfinder spacecraft entered the Martian atmosphere, slowed down by air friction, shed its heat shield, and floated down to the surface beneath a giant parachute. As soon as the dust settled — about an hour after touchdown — the landing capsule turned itself upright as it opened like a giant three-leaf clover. The leaves unfolded to reveal Pathfinder's cargo of sophisticated instruments: three solar panels to provide energy for its operations on the surface; a communications system to relay messages between Mars and Earth; a weather station to measure wind and temperature changes; and a 3-D panoramic camera mounted on a mast to scan and record the surrounding landscape. But the most fascinating device was Pathfinder's independent-minded hitchhiker, a microrover named Sojourner.

The six-wheeled vehicle, no larger than a microwave oven, operated as the eyes and wheels of the stationary lander. As its name suggests, it roamed around the landing site, exploring the rocks and soil in the vicinity. Its mission was to help scientists identify a wide variety of rocks on Mars. This so-called "ground truth" data cannot be obtained by distant observation. It will help scientists recognize the same minerals on other parts of the planet when viewed from orbiting spacecraft.

The landing itself was an experiment designed to show that a low-cost entry, descent, and landing system can safely put a spacecraft on Mars.

Company's Coming

On September 11,1997, a second American spacecraft arrived at the Red Planet. However, the Mars Global Surveyor (MGS) will keep its distance, orbiting the planet from pole to pole at an altitude of about 440 kilometers (248 miles). While Pathfinder examined the surface in minute detail, MGS will look at the larger picture, mapping the planet and studying the weather.

Pathfinder and MGS are following in some important footsteps. Two decades ago, two American spacecraft, Viking 1 and 2, landed on Mars. Most of what we know about the planet comes from the information they gathered. For example, it was Viking 2 that discovered water frost on the surface, the first evidence that water, though in a frozen state, could be found on Mars.

The Viking landing sites were north of the one chosen for Pathfinder, but lessons learned from the Viking missions helped planners settle on Pathfinder's landing site and design many aspects of the current mission. Now the lander and rover will join the Viking landers and the earlier Soviet Mars spacecraft as silent sentinels amid theshifting sands of the Red Planet. But the daily information that was sent back to Earth during Pathfinder's operation will enrich our understanding of Mars and enhance our ability to launch other missions of discovery for years to come.

Space Exploration on a Budget

Pathfinder was in the Martian vanguard of the Discovery Program, which the National Aeronautics and Space Administration (NASA) hopes will make space exploration affordable as we head into the next century. Each Discovery mission is designed to answer specific questions in a relatively short time period.