The Osiris-Rex probe successfully returns to earth with asteroid samples

Artist's impression of the sample collection carried out by the Osiris-Rex probe on the asteroid Bénou.

Osiris-Rex is back. After traveling more than 6 billion kilometers in space during its seven-year journey. After having closely accompanied and examined the asteroid Bénou. After taking 250 grams of samples from it in 2020. Sunday September 24, the NASA probe returned to our planet and released a small capsule containing its precious cargo, which landed shortly before 5 p.m. (Paris time). ) in a vast military zone of 9,300 km2 located in the Utah desert.

The maneuver was critical, which involved gently landing an object originally traveling at 44,500 km/h. It all started at 12:42 p.m., when Osiris-Rex, then a little more than 100,000 km from Earth, released the capsule weighing around fifty kilos into space. Four hours later, it began its entry into the Earth’s atmosphere. Friction with the air raised the temperature of its protective shield to around 2,800°C.

At an altitude of 31 km, a first parachute of 80 cm in diameter sprang from the rear of the capsule to stabilize it. A few minutes later, a second parachute measuring 7.3 m in diameter took over for the last 1,500 meters of descent. This entire journey was followed by radar and cameras so that the recovery team could find the capsule. The final destination of the samples will be the Lyndon B. Johnson Space Center in Houston (Texas) where the NASA division responsible for materials from elsewhere is located, such as lunar rocks from the Apollo missions, particles from the solar wind or meteorites.

For astronomers, samples taken from asteroids are valuable. As explained to Worldin 2019, Patrick Michel, CNRS research director at the Côte d’Azur Observatory and member of the Osiris-Rex scientific team, “asteroids are the remains of the bricks that built the planets”. Remains from the formation of the Solar System. Unlike planets which have heated up a lot and have chemically metamorphosed, asteroids are only slightly transformed and they somehow retain the memory of these primitive bricks.

Read our interview with Patrick Michel: Article reserved for our subscribers Patrick Michel: “The study of asteroids provides the recipe for the formation of planets”

A priori, the cargo of Osiris-Rex, even if it is not the first sample in situ of this kind, will be the largest ever reported. The very first attempt, led by Japan with the Hayabusa probe, ended in semi-failure: due to a series of problems, only 1,500 microscopic grains from the asteroid Itokawa returned to Earth in 2010. Its “daughter mission”, Hayabusa-2, was on the other hand a total success: it had collected a little more than 5 grams of material from the asteroid Ryugu. Much more than its initial goal of a fraction of a gram, but much less than Osiris-Rex with its estimated 250 grams. These will not be entrusted entirely to researchers: 70% of the harvest will be kept for later, while waiting for analysis techniques to have progressed.

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