the day Pathfinder “broke the Internet”

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Mars Pathfinder is a NASA mission launched in 1996. Unlike previous projects, the lander was also equipped with a rover called Sojourner. At the time, it was a first that had garnered a lot of attention.

Perseverance’s long journey is coming to an end. Launched on July 30, 2020, the rover is expected to land inside Jezero crater this Thursday, February 18. If successful, it will be the fifth NASA rover to land on Mars, after Sojourner (1997), twin rovers Spirit and Opportunity (2004) and Curiosity (2012). This is the first that interests us today.

The small rover Sojourner had been released on the red planet as part of the Pathfinder mission in 1997. NASA had already landed on Mars before with its two Viking landers in 1976. However, as their name suggests, they were “only” landers. In other words, these two machines remained static. In 1997, Sojourner was the whole first land vehicle to travel to another planet. And at the time, it made (a lot) of noise.

“Pathfinder broke the Internet”

The photos returned by the rover, operated by the Jet Propulsion Laboratory in collaboration with NASA, indeed quickly attracted public attention. In one day, Pathfinder sites set a record with 47 million visits, which is still very impressive by today’s standards. A demand that a still nascent World Wide Web simply could not meet.

Pathfinder broke the internet“, Recalls Jim Zimbelman, geologist emeritus at Smithsonian’s Center for Earth and Planetary Studies. “There were so many requests to upload photos that JPL was not ready to deal with them“.

By way of comparison, the 47 million views recorded on July 8 (the day of landing) was more than double the hits recorded the previous year on any day of the 1996 Olympic Games in Atlanta. Finally, NASA and JPL have set up some twenty “sister” sites to try to meet the demand and the curiosity of the public. In total, Pathfinder websites recorded 565 million visits worldwide between July 1 and August 4, 1997.

Public interest had started to rise the year before, when scientists announced the discovery of a Martian meteorite in Antarctica that contained signs of possible extraterrestrial life. NASA, which was preparing Pathfinder for a later launch, finally decided to advance the mission which took off for the Red Planet in December 1996.

View of the Pathfinder mission exploration site in Ares Vallis. We can clearly see on the horizon two hills called Twin Peaks. Credit: NASA / JPL

Land with airbags

This mission was also unusual for another reason. At the time, NASA and JPL were concerned that Pathfinder and Sojourner might not survive traversing the Martian atmosphere using only parachutes and retro-rockets. In addition, the researchers were concerned that the heat from the engines would “bake” the surface, ultimately preventing the collection of clean samples for analysis. Instead, they came up with a different solution: a airbag system.

Concretely, the Pathfinder mission relied on a combination of four descent methods. First of all, a heat shield was used when it entered the atmosphere of Mars. Of parachutes, then retro rockets were deployed to slow the ship. Then the lander and its rover, rolled up in huge air cushions, were released about twenty meters above the ground. Pathfinder then bounced fifteen to twenty times on the surface, before coming to a stop and opening up like flower petals, ultimately delivering the Sojourner rover to the surface of Mars.

It was the first use of this type of landing, the airbag assisted landing“Says Matt Shindell, curator of space history at the Smithsonian Museum. “They used it on subsequent missions, but in 1997 it was the first time they tried this particular engineering solution.“.

The Pathfinder prototype on display at the Udvar-Hazy Center, Air and Space Museum in Chantilly, Virginia. Credit: NASM

The goal of Pathfinder was to prove the viability of “fast and cheap” missions. It only cost $ 150 million and was developed in less than three years. On site, the rover made it possible to study the surface of Mars, including the geochemistry of rocks, the magnetic properties of the surface and the structure of the planet’s atmosphere.

The rover returned a treasure trove of information, collecting no less 1.2 gigabytes of data and taking around 10,000 photos of the Martian surface. Designed to last only a month, the solar-powered rover still held up to 70 Martian soils, or 85 earth days. It returned its last transmission to Earth on September 27, 1997.

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