Since the Viking probes of 1970s, Mars Pathfinder was the first in a series of (relatively) small and inexpensive spacecraft scheduled to reach Mars. When Mars Pathfinder landed in 1997, the mission received a huge amount of attention from the public. In fact, more than 47 million people visited the website that NASA dedicated to Mars Pathfinder! [slightly more visitors than we receive]
The Unique Design
The Mars Pathfinder was made of a closed container with four triangular sides. When it landed on the planet's surface, the container would open up and expose its three solar panels and instruments. At the center, there would also be the small wheeled rover, called Sojourner.
The solar panels converted sunlight into electricity for Pathfinder's systems and instruments. These instruments included Pathfinder's color camera. The camera would simultaneously take two photos from slightly different viewpoints to produce three-dimensional images.
The rover Sojourner had 6 wheels and a mass of 10 kg (22 lb). Sojourner had its own rectangular solar panel on top and carried an Alpha Proton X-ray (APXR) device. The APXR aimed alpha particles at rocks and determined the rock's composition from the radiation that bounced back. Sojourner also had its own camera and laser system, which was used to automatically avoid obstacles and find a path to the target rock.
The Pathfinder Mission
Mars Pathfinder lifted off on a Delta II rocket on December 4, 1996. Seven months later, it reached Mars and entered the atmosphere. About 8 km (5 mi) above the surface, the parachute opened and slowed the decent. At 21m (24.5 yd) from the surface, the parachute detached and airbags were used for the rest of the way. Pathfinder bounced for about 1 km before finally coming to a stop.
From that spot, the airbags deflated and the container opened. Almost immediately, Sojourner moved 40 cm (15.75 in) to a rock (later named "Barnade Bill") and analyzed the rock using APXR. Meanwhile, the cameras aboard Pathfinder photographed the Twin Peaks, two hills about 1.6 km (1 mi) away. Later, Sojourner studied the composition of a boulder named Yogi and used its wheels to dig into the Martian surface.
The mission continued until October 7, when Pathfinder sent its last signal to Earth. Engineers believed that the onset of Martian autumn caused the temperature to fall below the point in which the transmitter could operate.
Pathfinder: The Pioneer of Rovers
Through the Pathfinder mission, we have learned much more about Mars and its past. Using the APXR instrument on Sojourner, scientists to found that the rocks are possibly young volcano rocks. This signifies that Mars has been geologically active in the recent past. Also, a distribution of rocks at the site indicated that a giant flood laid them down.
Scientist tracked Pathfinder's location as Mars rotated and orbited the Sun. Through this, scientists learned more about the irregularities in Mar's orbit and location. From the data gathered, scientists were able to estimate Mar's core to be 1300-2000 km (807-1242 mi) across.
Other than the scientific data, Pathfinder also made great advances in space robotics. The technology gained in this mission will be used in future missions. For example, the untried airbag landing system worked flawlessly.
On the other hand, Sojourner, the rover, was extremely slow. Sojourner needed about three months to travel less than 90 meters! Nevertheless, it demonstrated that rovers could be used to explore Mars and other planets. Engineers predict that the next generation of Mars rovers will be able to travel thousands of kilometers and will aid humans in the exploration of Universe.
