Martian rovers are remote-controlled motor vehicles that are designed to travel the Martian surface and help us better understand our neighbouring red planet. You might have heard about the Curiosity and Perseverance rovers, NASA’s rovers that are currently active on the surface of Mars. And then there are the rovers of the past, NASA’s Spirit and Opportunity and the Chinese rover called Zhurong.
The first Martian rover and, in fact, the first wheeled vehicle to be used on any other planet in the solar system was NASA’s Sojourner. Part of NASA’s Mars Pathfinder mission, it helped NASA develop foundational technologies for the future and thereby started modern exploration of Mars in a way.
Fraction of the cost
Launched on December 4, 1996, both the lander and the 10.6 kg rover carried scientific instruments. These included not only those that would enable observations on Mars, but also those that were capable of providing engineering data on the new tech that was employed in it.
While the successful Viking 1 and 2 Mars missions of the 1970s required billions of dollars (inflation-adjusted), the Pathfinder was relatively low-cost at less than half a billion dollars. A lot, therefore, hinged on its success as this meant that the scientists and engineers could adopt this low-cost technique for future missions as well.
The Pathfinder’s landing system used an innovative method to get on the Martian surface. As opposed to going by the conventional way of using rockets to slow down and touch down on Mars, a cocoon of protective airbags were instead tasked with it.
These airbags were inflated just eight seconds before the landing on July 4, 1997. Dropping down from a distance of about 30 m from the ground, the Pathfinder, enveloped in airbags, bounced across the Martian surface for a number of minutes before safely rolling over to a standstill.
Following its successful landing, the lander was formally named the Carl Sagan Memorial Station in honour of the science populariser Carl Sagan, who had died just a couple of weeks after Pathfinder’s launch, on December 20, 1996. The rover, meanwhile, was named Sojourner after American civil rights activist Sojourner Truth.
Cartoon character rocks
Even though solemn names were given to the lander and the rover, the rocks that these encountered were named after cartoon characters. Sojourner’s analysis of “Barnacle Bill” showed that it had more silica than its surrounding environment. This led NASA scientists to suggest that Mars might have had a more interesting geological past than what was thought possible before. Though the results could have been affected by dust on the rocks, analysis showed “Yogi” to be a basalt and “Scooby-Doo” as sedimentary.
Even as Sojourner went about its business, the Pathfinder continued to do its duty, relaying information both from itself and the rover back to Earth, and clicking countless pictures. This included a sunset showing blue colour near the sun, caused by scattering in the dusty atmosphere of Mars. The magnetic properties of the dust were also measured by the equipment on board.
Thousands of pictures
The Pathfinder communicated with NASA until September 27, 1997, with the agency suspecting a dead battery as the cause for the failure. During its time on Mars, Sojourner travelled close to 100 m, without ever going more than 12 m away from the lander. While the rover captured 550 images, the lander relayed back over 16,500 pictures.
Both the lander and the rover outlived the expectations of their primary design life – the lander by nearly three times, and the rover by 12 times. In addition to the airbag landing technique, the Mars Pathfinder also taught scientists that rovers had to be sufficiently autonomous to take into account the two-way Earth-Mars communication lag of up to 42 minutes. The success of the Mars Pathfinder mission thus laid the seeds for modern Mars exploration.