2023-09-24 03:37:00
It’s the end of a journey that began seven years ago: the largest asteroid sample ever collected, and the first for NASA, is due to land on Sunday in the Utah desert, in the United States.
The final descent through the Earth’s atmosphere promises to be perilous, but the American space agency hopes that it will result in a smooth arrival, around 9:00 a.m. local time (3:00 p.m. GMT), on a military area usually used for testing missiles.
After taking off in 2016, the Osiris-Rex probe collected stones and dust from the asteroid Bennu in 2020.
Some 250 grams of material (+ or – 100 grams), according to NASA’s estimate, which should “help us better understand the types of asteroids that could threaten the Earth”, and shed light on “the very beginning of the history of our solar system”, underlined the boss 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 from lunar rocks” from the Apollo program, concluded in 1972.
But before accessing the precious cargo, the maneuver to be carried out is “dangerous”, she admits.
The Osiris-Rex probe must release the capsule containing the sample four hours before landing, more than 100,000 km from Earth.
During the last 13 minutes, this capsule will cross the atmosphere: it will enter at more than 44,000 km/h, with a temperature rising to 2,700°C.
The fall, observed by army sensors, will be slowed by two successive parachutes, of which it is essential that they deploy correctly to avoid a “hard landing”.
It could be decided at the last moment not to release the capsule if it appears that the targeted area (58 by 14 km) will be missed. The probe would then go around the Sun, before trying its luck again in 2025. But if its delivery goes well, it will set off for another asteroid.
– Two Japanese samples –
Once the capsule is on the ground, a team equipped with gloves and masks will check its condition, before placing it in a net, then lifted by a helicopter and taken to a temporary “clean room”.
The capsule must be exposed to the sand of the American desert for as short a time as possible, in order to avoid any contamination of the sample which could distort subsequent analyses.
On Monday, it will be flown to the Johnson Space Center in Houston, Texas. This is where the box will be opened, in another airtight room. The process will take days.
NASA is planning a press conference on October 11 to reveal initial results.
The majority of the sample will be preserved for study by future generations. About 25% will be immediately used for experiments, and a small part will be shared with partners Japan and Canada.
Japan itself gave NASA some grains from the asteroid Ryugu, of which it reported 5.4 grams in 2020, during the Hayabusa-2 mission. In 2010, he reported a microscopic amount from another asteroid.
This time, the Bennu sample is “much bigger, so we will be able to do a lot more analysis,” said Amy Simon.
– History of our origin –
Asteroids are composed of the original materials of the solar system, 4.5 billion years ago. Unlike Earth, they remained intact.
They therefore hold “clues about how the solar system formed and evolved,” Melissa Morris, head of the Osiris-Rex program at NASA, said at a press conference. “It is the story of our own origin.”
By hitting our planet, “we think that asteroids and comets brought organic matter, potentially water, that helped life develop on Earth,” explained Amy Simon.
Scientists believe that Bennu (500 meters in diameter) is rich in carbon, and contains water molecules locked in minerals.
The asteroid also surprised scientists: its surface turned out to be less dense than expected during sample collection. The arm of the probe had sunk, a bit like in a ball pit.
However, better understanding its composition could prove useful in the future.
There is a small risk (1 chance in 2,700) that Bennu will hit Earth in 2182, a collision that would be catastrophic. But last year NASA managed to deflect the trajectory of an asteroid by hitting it.
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