It is the end of a journey that began seven years ago: the largest asteroid sample ever collected and the first for NASA is scheduled to land in the Utah desert in the USA on Sunday.
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The final descent through Earth’s atmosphere promises to be dangerous, but the American space agency hopes it will arrive smoothly at around 9:00 a.m. local time (3:00 p.m. GMT) at a military site normally used for testing rockets.
After launching in 2016, the Osiris-Rex probe collected rocks and dust from the asteroid Bennu in 2020.
According to NASA’s estimate, about 250 grams of material (+ or – 100 grams) that should “help us better understand the types of asteroids that could threaten Earth” and shed light on “the beginnings of our sun’s history.” System,” emphasized the head of the space agency, Bill Nelson.
“The return of this sample is truly historic,” NASA scientist Amy Simon told AFP. “This will be the largest sample we bring back of lunar rocks” from the Apollo program that concluded in 1972.
But before you can get to the precious cargo, the maneuver to be carried out is “dangerous,” she admits.
Four hours before landing, more than 100,000 km from Earth, the Osiris-Rex probe must release the capsule containing the sample.
In the last 13 minutes, this capsule will cross the atmosphere: it will enter at more than 44,000 km/h, with the temperature rising to 2700 °C.
The crash, observed by Army sensors, is slowed by two successive parachutes, the correct deployment of which is essential to avoid a “hard landing.”
It could be decided at the last moment not to release the capsule if it appears that the target area (58 x 14 km) will be missed. The probe would then orbit the sun before trying its luck again in 2025. But if the delivery goes well, it will make its way to another asteroid.
Once the capsule is on the ground, a team equipped with gloves and masks checks its condition before it is placed in a net, then lifted by a helicopter and taken to a makeshift “clean room.”
The capsule must be exposed to the sands of the American desert for as short a time as possible to avoid contamination of the sample, which could confound subsequent analyses.
On Monday it will be flown to the Johnson Space Center in Houston, Texas. Here the box is opened in another airtight room. The process will take days.
NASA is planning a press conference on October 11 to announce initial results.
The majority of the sample will be retained for study by future generations. About 25% will be used immediately for experiments and a small portion will be shared with partners Japan and Canada.
Japan itself gave NASA some grains of the asteroid Ryugu during the Hayabusa-2 mission, of which it returned 5.4 grams in 2020. In 2010, he reported a microscopic amount from another asteroid.
This time, the Bennu sample is “much larger, so we can do a lot more analysis,” Amy Simon said.
Asteroids are made from the primordial materials of the solar system 4.5 billion years ago. Unlike Earth, they remained intact.
They therefore have “clues to how the solar system formed and evolved,” said Melissa Morris, head of NASA’s Osiris-Rex program, at a press conference. “It is the story of our own origins.”
By impacting our planet, “we believe that asteroids and comets brought organic matter, possibly water, that contributed to the development of life on Earth,” explained Amy Simon.
Scientists believe Bennu (500 meters in diameter) is rich in carbon and contains water molecules trapped in minerals.
The asteroid also surprised scientists: its surface turned out to be less dense than expected when the sample was taken. The arm of the probe was sunken, a bit like a ball pit.
However, a better understanding of its composition could prove useful in the future.
There is a small chance (1 in 2700 chance) that Bennu will hit Earth in 2182, a collision that would be catastrophic. But last year, NASA managed to divert the trajectory of an asteroid by hitting it.