Experimentation

Since its landing on July 4, 1997, Mars Pathfinder had returned 2.6 billion bits of information, including more than 16,000 images from the lander and 550 images from the rover, as well as more than 15 chemical analyses of rocks and extensive data on winds and other weather factors. The only remaining objective was to complete the high-resolution 360-degree image of the landing site called the "Super Pan," of which 83 percent has already been received and is being processed.

Loss of Contact

The last successful data transmission cycle from Pathfinder was completed at 3:23 a.m. Pacific Daylight Time on Sept. 27, 1997. At the time the last telemetry from the spacecraft was received, Pathfinder's lander had operated nearly three times its design lifetime of 30 days, and the Sojourner rover operated 12 times its design lifetime of seven days.

Other Achievements

Part of NASA's Discovery program of low-cost planetary missions, the spacecraft used an innovative method of directly entering the Martian atmosphere. Assisted by an 11-meter-diameter (36-foot) parachute, the spacecraft descended to the surface of Mars on July 4 and landed, using airbags to cushion the impact. The spacecraft's novel entry was successful.

Scientific Highlights

• Martian dust includes magnetic, composite particles, with a mean size of one micron.
• Rock chemistry at the landing site may be different from Martian meteorites found on Earth, and could be of basaltic andesite composition.
• The soil chemistry of Ares Vallis appears to be similar to that of the Viking 1 and 2 landing sites.
• The observed atmospheric clarity is higher than was expected from Earth-based microwave measurements and Hubble Space Telescope observations.
• Dust is confirmed as the dominant absorber of solar radiation in Mars' atmosphere, which has important consequences for the transport of energy in the atmosphere and its circulation.
• Frequent "dust devils" were found with an unmistakable temperature, wind and pressure signature, and morning turbulence; at least one may have contained dust (on Sol 62), suggesting that these gusts are a mechanism for mixing dust into the atmosphere.
• Evidence of wind abrasion of rocks and dune-shaped deposits was found, indicating the presence of sand.
• Morning atmospheric obscurations are due to clouds, not ground fog; Viking could not distinguish between these two possibilities.
• The weather was similar to the weather encountered by Viking 1; there were rapid pressure and temperature variations, downslope winds at night and light winds in general. Temperatures were about 10 degrees warmer than those measured by Viking 1.
• Diversity of albedos, or variations in the brightness of the Martian surface, was similar to other observations, but there was no evidence for the types of crystalline hematite or pyroxene absorption features detected in other locations on Mars.
• The atmospheric experiment package recorded a temperature profile different than expected from microwave measurements and Hubble observations.
• Rock size distribution was consistent with a flood-related deposit.
• The moment of inertia of Mars was refined to a corresponding core radius of between 1,300 kilometers and 2,000 kilometers (807 miles and 1,242 miles).
• The possible identification of rounded pebbles and cobbles on the ground, and sockets and pebbles in some rocks, suggests conglomerates that formed in running water, during a warmer past in which liquid water was stable.