There is a place in the middle of the Utah desert, in the USA, with unusual activity this Sunday. The reason? The imminent arrival on Earth of an authentic scientific treasure, equivalent to a time capsule. It is expected that around 17 hours (Spanish peninsular time) a capsule will land with a quarter of a kilo of Bennu material, an asteroid about 500 meters in diameter whose composition will be able to be analyzed in detail with the most sophisticated instruments of terrestrial laboratories to investigate the origin of our solar system.

The samples have been collected by the OSIRIS-REx robotic spacecraft that, after a seven-year adventure, culminates the mission today with an exciting and complex landing before which NASA researchers hold their breath.

"It's the first time that the U.S. is going to bring samples collected from an asteroid back to Earth," Lucas Paganini, a NASA planetary scientist and one of the team members deployed at the U.S. Army base Dugway, a military testing ground near Salt Lake City, said in an interview by videoconference.

Until now only the Japanese had managed to bring material from one of these celestial bodies to Earth, through the robotic Hayabusa 2 mission, which in December 2020 brought to our planet 5.4 grams of rocks and dust from the asteroid Ryugu. The pioneer was its bumpy sister mission Hayabusa 1, which in 2010 became the first probe to bring particles from an asteroid to Earth for analysis. However, due to various technical problems, instead of getting several grams of dust, it brought less than a milligram of particles that were also contaminated by material from the ship itself.

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The requirement of the OSIRIS-REx mission was to bring 60 grams of Bennu, we know that it has collected 250 grams and it will be the largest sample brought from an asteroid, "says the Argentine Paganini, who joined NASA in 2010 after studying Electronic and Telecommunications Engineering at the University of Mendoza and obtaining a doctorate at the University of Fribourg.

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  • Writing: TERESA GUERRERO Madrid

This is the new space race: bringing alien rocks to Earth

The OSIRIS-REx spacecraft lifted off on September 8, 2016 bound for the asteroid Bennu, which it arrived at two years later, in August 2018. He then spent two more years studying it, scanning it and making a map that helped scientists locate where the spacecraft should take the samples, which it captured on Oct. 20, 2020. Now at last, they are going to come to Earth.

"We are very excited and it is a joy to be here, in Dugway, and share this Sunday with people the arrival of the capsule with the samples of Bennu," says this scientist, who will participate in the broadcast in Spanish of the complicated landing of the capsule.

The interview with Lucas Paganini took place last Friday. He says that it is quite cold in the Utah desert, about eight degrees, and although for this Sunday higher temperatures were expected, he explains that regardless of the weather the capsule will land today.

At the moment everything is going according to plan. As expected, at 12.42 (CET), when the OSIRIS-REx spacecraft was about 102,000 kilometers from Earth, the capsule has been released from the probe. About 20 minutes after releasing the container with the samples, the spacecraft turned on its engines to deflect its trajectory and begin a new mission, called OSIRIS-APEX (OSIRIS-Apophis Explorer) to explore the asteroid Apophis, which it will arrive in 2029. Meanwhile, the capsule with the samples continues on its way to Earth.

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It will descend ballistically, and once it enters the Earth's atmosphere, it will take between 13 and 15 minutes to land. Through a parachute system it will reduce speed, as it will travel at more than 40,000 kilometers per hour, "he details.

Specifically, the capsule will enter the Earth's atmosphere at 44,500 kilometers per hour four hours after being released from the spacecraft. NASA expects this critical phase to occur at 16:42 p.m. and is expected to land 13 minutes later. The area of the desert in which the capsule will fall comprises an ellipse of about 60 kilometers by 15 kilometers: "There have been many studies and previous calculations, and the mission has been rehearsed a lot, so although the chances of error are never zero, they are very low," he says.

The decisive moment and therefore the most complicated phase will be the detachment of the parachutes so that the capsule decelerates: "If they do not detach, the safety of the capsule can be compromised because it would be a very hard landing that could damage it," he warns. The capsule, adds Paganini, "has a special heat shield that allows the samples to be kept at a stable temperature" and not be altered during re-entry into the atmosphere.

Recreation of one of the parachutes that will be deployed during the landing of the capsule

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We know that the capsule contains pristine material and now we will be able to study it with the high-precision instruments that we have in laboratories on Earth but that we cannot have in spacecraft," says the NASA researcher.

Therefore, the treatment given to the container once it lands is essential to keep the samples in perfect condition. Around a hundred people and two helicopters are part of the deployment to recover the capsule and broadcast its arrival. The rescue operation of the samples will begin with a rapid action to recover them as soon as possible and reduce the chances of the container being contaminated when it comes into contact with the earth's surface. Military and NASA personnel will place the capsule in a metal box and wrap it in several layers of a non-reactive plastic material, first, and then in a tarp.

A harness will then be placed over the box to secure it to a cable attached to a helicopter, which will transfer it to a mobile clean room at the Utah base to check that it is in good condition. In this clean room they will open the capsule, extract the container with the sample and prepare it for Monday to be transferred to NASA's Johnson Space Center in Houston, which will be where most of the samples will be kept.

NASA's plan, says Paganini, is that 25% of the material will be distributed among the 233 scientists of the mission. On the other hand, the Canadian Space Agency will keep 4% and theJapanese agency, JAXA, will be given 0.5%. A small portion of the sample will also be stored in White Sands, New Mexico, for safekeeping. The rest, about 70%, "will be preserved for posterity, for when better instruments become available and for future scientists to study," says Paganini.

Why is it so important to study asteroids? "They are fossils or time capsules, the remnants of the formation of planets and moons that took place 4.600 billion years ago. These challenges allow us to understand how they were formed and in addition, we have theories that maintain that asteroids or comets could bring to Earth the essential elements for the beginning of life, such as carbon, hydrogen, oxygen or even water, "says this NASA scientist.

The other important aspect, he adds, is planetary defense: "The study of these components allows us to better understand their composition in the face of possible asteroids that may have a dangerous course for the Earth," he says.

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