Pathfinder and Sojourner at Ares Vallis

Mars Pathfinder and Sojourner · 1997 CE · Mars

Pathfinder and Sojourner at Ares Vallis — Mars Pathfinder and Sojourner · 1997 CE · Mars — Recorded expedition route · schematic map

Prove a low-cost way of landing on airbags and drive a small rover between rocks.

Historical context

Twenty-one years after Viking 1, NASA returned to the surface of Mars with Pathfinder, the second mission of its Discovery programme of low-cost spacecraft, which cost about 265 million dollars including launch and operations. Its job was to prove a new way of landing, straight in from its flight path and onto airbags, and to carry a small rover named Sojourner as a technology experiment. Pathfinder came down in Ares Vallis on 4 July 1997 and worked until 27 September, the first of a series of spacecraft NASA planned to send to Mars every twenty-six months.

The voyage, step by step

  1. At least fifteen bounces

    4 July 1997

    On 4 July 1997 the spacecraft dived straight into the Martian air from its path from Earth, slowed behind its heat shield and under its parachute, wrapped itself in airbags and fired three rockets about a hundred metres up. It hit Ares Vallis at 16:56:55 Universal Time, as the event happened on Mars, at about fourteen metres a second, fifty kilometres an hour by NASA’s figures, and bounced at least fifteen times before rolling to a stop.

  2. Carl Sagan Memorial Station

    4 July 1997

    Eighty-seven minutes after landing, still in the dark, the lander had drawn in its airbags and opened its three petals of solar cells on an ancient flood plain, among rounded and stacked stones. The next day NASA named it the Carl Sagan Memorial Station.

  3. Down the ramp

    6 July 1997

    Late on sol 2, on the night of 5 July by Pacific time, the six-wheeled rover stood up to its full height of thirty centimetres and backed down the lander’s rear ramp onto the soil. Sojourner weighed ten and a half kilograms by NASA’s chronicle, 10.6 by the press kit, and moved at a centimetre a second.

  4. Barnacle Bill

    1997 CE

    Sojourner’s first rock was a small one beside the lander, named Barnacle Bill for its rough surface. On sol 3 the rover set its alpha proton X-ray spectrometer against it, a measurement that took about ten hours. Its chemistry, unexpectedly rich in silica, resembled terrestrial andesite.

  5. Yogi

    1997 CE

    Yogi, a large rock three or four metres from the lander, came next. Over sols 8 to 10 Sojourner held its spectrometer against it, and the early results, NASA said, showed a rock more primitive than Barnacle Bill, more basaltic and more like the common basalts of Earth.

  6. A flood plain read from the ground

    27 September 1997

    The last successful data transmission ended at 3:23 in the morning, Pacific Daylight Time, on 27 September 1997, after eighty-three sols. The lander had worked nearly three times its design life of thirty days, and Sojourner twelve times its seven.

Outcome

Eighty-three sols of work, more than 16,500 lander images, 550 rover images and sixteen chemical analyses of rocks and soil.

Mars Pathfinder and Sojourner

Airbag lander that set down in Ares Vallis on 4 July 1997 and released Sojourner, by Siddiqi’s chronicle the first wheeled vehicle on Mars.

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