A Robot Explores Mars
MY FAMILY and I watched excitedly as the rocket carrying the Mars Pathfinder spacecraft blasted off from its launchpad at Cape Canaveral, Florida. We wondered, ‘Will it land successfully on Mars? What new discoveries await?’
Concern for the success of Pathfinder was based in part on the previous two missions to Mars, by Mars Observer and Mars 96, both of which failed. Moreover, Pathfinder was to attempt an unprecedented hard landing.
The spacecraft began plunging into the Martian atmosphere at nearly 17,000 miles per hour [27,000 km/hr]. After deploying a parachute to make it decelerate and then descending to an altitude of about 320 feet [98 m], it fired rockets to slow itself even further. Meanwhile, a protective cushion of large air bags filled with gas was provided for the spacecraft. On July 4, 1997, at a speed of 40 miles an hour [65 km/hr], Mars Pathfinder impacted the Martian surface.
The first bounce lifted the spacecraft some 50 feet [15 m]. After bouncing like a huge beach ball another 15 times or so, it came to rest. The air bags then deflated and retracted. Although designed to right itself if necessary, Pathfinder happened to land right side up. Finally, it unfurled its flowerlike petals, revealing scientific instruments, radio antennas, solar panels, and a rover named Sojourner.
Soon Pathfinder’s camera surveyed the surrounding landscape. Nestled in a broad plain named Chryse Planitia, meaning “Plains of Gold,” near an area called Ares Vallis, or “Mars Valley,” Pathfinder revealed a rocky, rolling surface and distant hills—ideal for exploration by Sojourner. This able little robot, 25 inches [65 cm] in length, was to perform visual investigations with its camera and measure the amounts of chemical elements in rocks and soils with a spectrometer.
The mission scientists and engineers initiated the exploration by Sojourner. Since radio signals take many minutes to travel between Earth and Mars, mission operators could not drive Sojourner directly. Sojourner therefore relied heavily on its own ability to avoid hazards of the Martian terrain. It did this by using laser beams to determine the size and location of rocks in its path. Then its computer would direct it either to drive over the rocks if they were small enough or to take a detour if they were too large.
Adventure and Discovery
Reports in newspapers and magazines treated millions to Pathfinder’s pictures of the Martian surface. As new scenes from Mars arrived, people on earth were entertained by the antics of the wandering rover, intrigued by color panoramas of the rocky and hilly landscape, and enthralled with views of clouds and sunsets in the Martian sky. During the first month of the mission, the Pathfinder’s Web page on the Internet recorded more than 500 million “hits” by people interested in the activities of the spacecraft.
Pathfinder produced a flood of data, even surpassing the expectations of mission scientists. This in spite of operating in temperatures ranging from about freezing, 32 degrees Fahrenheit, to a frigid -110 degrees Fahrenheit [-80°C]. What did this mission reveal?
Cameras and instruments discovered rocks, soils, and airborne dust of varying chemical compositions, colorations, and textures, indicating that complex geologic processes have operated on Mars. Small dunes in the surrounding landscape testified to the accumulation of loose sand deposited by northeasterly winds. The sky displayed predawn clouds made up of particles of water ice. As the clouds dissipated and dawn arrived, the sky acquired a reddish hue because of fine dust in the atmosphere. Occasionally, dust devils, swirls of wind and dust, passed over the spacecraft.
Mars Pathfinder has treated us to an experience that is literally out of this world. The United States and Japan plan more missions to Mars throughout the next decade. An orbiter, Mars Global Surveyor, has since arrived at Mars to conduct other scientific investigations. Indeed, Mars will become an increasingly familiar sight as we tour the red planet through the eyes of robotic spacecraft.—Contributed.
[Pictures on page 26]
All pictures: NASA/JPL