Mars - Mars Pathfinder

Mars Pathfinder was a mission conducted as part of NASA's Discovery program. This was the agency's "faster, better, cheaper" approach to space science. The mission was developed in only three years and cost $265 million. On December 4, 1996, the spacecraft launched atop a Delta II rocket from the Cape Canaveral Air Station in Florida. Pathfinder traveled for seven months before entering into the gravitational influence of Mars.

On July 4, 1997, the spacecraft was ordered to begin its descent to the planet's surface. A giant parachute released to slow its fall. A landing craft separated from the spacecraft shell and began to drop. Eight seconds before hitting the ground the lander's air bags deployed around it like a cocoon to cushion its impact on the surface. The lander ball bounced and rolled for several minutes before coming to a stop more than half a mile from where it first impacted. It was in a rocky flood plain known as Ares Vallis (Valley of Ares).

After the successful landing NASA renamed the lander the Carl Sagan Memorial Station, in memory of the late astronomer Carl Sagan (1934–96). He died while Pathfinder was en route to Mars. The lander unfolded three hinged solar panels onto the ground, as shown in Figure 7.1. It released a small six-wheeled rover named Sojourner that began exploring the nearby area. The name resulted from a NASA contest in which schoolchildren proposed names of historical heroines for the mission. The winning entry suggested Sojourner Truth, an African-American woman who crusaded for civil rights during the 1800s.

For two and a half months the Sojourner rover collected data about Martian soil, radiation levels, and rocks. The robotic machine weighed twenty-three pounds and FIGURE 7.1 The Pathfinder spacecraft "Pathfinder Spacecraft," in NASA Facts: Mars Pathfinder, National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, May 1999, http://www.jpl.nasa.gov/news/fact_sheets.cfm (accessed January 14, 2004)could move at a top speed of two feet per minute. It was powered by a flat solar panel that rested atop its frame. (See Figure 7.2.)

Meanwhile the lander collected images and relayed data back to Earth. It also measured the amount of dust and water vapor in the atmosphere. The lander's forty-inch mast held little wind socks at different heights to determine variations in wind speed near the planet's surface. Magnets were mounted along the lander to collect dust particles for analysis. Scientists learned that airborne Martian dust is very magnetic and may contain the mineral maghemite, a form of iron oxide.

The Pathfinder returned more than 17,000 images and performed fifteen chemical analyses. Scientists studying this data concluded that Mars might have been warm and wet sometime in the past with a thicker, wetter atmosphere. In late September 1997, Pathfinder sent its last message home.