15th Anniversary of Pathfinder Landing

The above image is a panoramic view taken by the Pathfinder cameras. At center is the Sojourner rover at its first major target, a big rock nicknamed "Yogi Rock." The rocks found on this mission were named after famous icons and figures. Yogi was the first rock found on Mars to be made of basalt. Image Credit: NASA

Happy anniversary, Mars Pathfinder! On July 4th, 1997, NASA's Mars Pathfinder mission successfully landed on the surface of Mars. The event marked the first successful U.S. landing on the Red Planet since NASA's Project Viking missions of the 1970s. Originally named the Mars Environmental Survey (MESUR) Pathfinder mission, Mars Pathfinder consisted of a lander, later renamed the Carl Sagan Memorial Station, and a lightweight (10.6 kilograms/23 pounds) wheeled robotic rover named Sojourner.

Mars Pathfinder launched on December 4th, 1996 aboard a Delta II booster, one month after the launch of the Mars Global Surveyor (MGS), a Mars orbiter mission. Pathfinder landed on Mars' Ares Vallis, in a region called Chryse Planitia in the Oxia Palus quadrangle. The lander then opened, exposing the rover which conducted many experiments on the Martian surface. Pathfinder was the second project from NASA's Discovery Program, which promotes the use of low-cost spacecraft and frequent launches under the motto "cheaper, faster and better," which was promoted by the then administrator, Daniel Goldin. Mars Pathfinder was directed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology, responsible for NASA's Mars Exploration Program.

In addition to its scientific objectives, Mars Pathfinder was also a "proof-of-concept" for various technologies, such as airbag-mediated touchdown and automated obstacle avoidance, both later exploited by the Mars Exploration Rovers (Spirit and Opportunity). Pathfinder was also remarkable for its extremely low cost relative to other unmanned space missions to Mars.


After the landing, Pathfinder was renamed as the Sagan Memorial Station in honor of astronomer and planetologist Carl Sagan. On Sol 2 (the second Martian day on the surface), the Sojourner rover rolled off the lander. The little rover then made its way to a grouping of rocks, which the scientists named "Barnacle Bill", "Yogi", and "Scooby Doo", after famous cartoon characters. Sojourner made measurements of the elements found in those rocks and in the martian soil, while the lander took pictures of the Sojourner and the surrounding terrain, in addition to making climate observations.

Sojourner had six wheels, was 65 cm long, 48 cm wide, 30 cm tall and weighed 10.5 kg. Its maximum speed reached one centimeter per second. Sojourner traveled approximately 100 meters in total, never more than 12 meters from the Pathfinder station. During its 83 sols of operation, it sent 550 photographs to Earth and analyzed the chemical properties of 16 locations near the lander.


Although the mission was programmed to last from a week to a month, it lasted for almost three months. The final contact with Pathfinder was at 10:23 UTC on September 27th, 1997. Although mission managers tried to restore contact during the five months that followed, the mission was terminated on March 10th, 1998. The mission had exceeded its goals in the first month.

The official name for "the little rover that could" was chosen after a year-long, worldwide competition in which students up to 18 years of age were invited to submit an essay about a heroine of their choosing. First prize went to Valerie Ambroise, age 12, who wrote about Sojourner Truth, a black reformist who lived during the Civil War era. An abolitionist and champion of women's rights, Sojourner Truth, whose legal name was Isabella Van Wagener, made it her mission to "travel up and down the land," advocating the rights of all people to be free and the rights of women to participate fully in society. The name Sojourner means "traveler."

Second prize went to Deepti Rohatgi, age 18, who wrote about Marie Curie, the Polish-born chemist who won the Nobel Prize in 1911 for her discovery of the elements radium and polonium. This name was given to an identical rover which was used in testing on Earth by the mission team. Third prize went to Adam Sheedy, age 16, who wrote about the late NASA astronaut Judith Resnik.

To learn more about the Mars Pathfinder mission, visit the mission archives at this URL: mars.jpl.nasa.gov/MPF . To lean more about the planet Mars and more about NASA's Exploring Mars Program, visit these URLs: marsprogram.jpl.nasa.gov/ and marsrovers.jpl.nasa.gov .

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