2023-09-23 14:53:28
This is the first time that NASA has brought an asteroid sample back to Earth, and it is a priori the largest ever collected: seven years following its takeoff, the Osiris-Rex mission must deliver its precious cargo to the desert on Sunday from Utah, United States. Thanks to the analysis of this material collected in 2020 on the asteroid Bennu, scientists hope to better understand the formation of the solar system, and how the Earth became habitable.
The landing is due to take place on Sunday around 9 a.m. (3 p.m. GMT), on a military zone normally used to test missiles. About four hours earlier, more than 100,000 km from Earth, the Osiris-Rex probe must release the capsule containing the sample.
The final descent into the Earth’s atmosphere will last 13 minutes: the capsule will enter at a speed of around 44,000 km/h, and the friction caused will raise the temperature to 2,700°C.
The targeted area is 58 km long and 14 km wide. It’s like “throwing a dart across a basketball court and hitting the center of the target,” Rich Burns, mission manager at NASA’s Goddard Space Flight Center, said at a press conference in late August. .
It may be decided not to release the capsule if it appears the night before that the selected area will be missed. The probe would then circle the Sun, before trying its luck once more in 2025.
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250 grammes ?
Osiris-Rex took off in 2016, and in 2020, the asteroid Bennu surprised scientists when collecting the sample: during contact with the surface for a few seconds, the arm of the probe sank into the soil, revealing a much lower density than expected. But thanks to this, NASA expects to recover some 250 grams of material — much more than the initial objective of 60 grams.
This is “the largest mass collected beyond the orbit of the Moon”, underlined Melissa Morris, head of the program. This mission is a first for the United States, but Japan has already carried out two similar ones: in 2010, the Hayabusa probe reported microscopic grains from the asteroid Itokawa. And Hayabusa-2 reported in 2020 some 5.4 grams from the asteroid Ryugu.
Visually, the asteroid Bennu resembles Ryugu, but might turn out to be very different in its composition, according to Melissa Morris. Asteroids are of interest because they are composed of the original materials of the solar system, 4.5 billion years ago. While on Earth these have been transformed, the asteroids have remained intact. Bennu is rich in carbon, and the sample collected is “perhaps representative of the seeds of life that these asteroids delivered at the beginning of our planet, which led to this incredible biosphere,” said Dante Lauretta, chief scientist. of the mission at the University of Arizona.
Bennu, which is 500 meters in diameter, orbits the Sun and approaches Earth every six years. There is a small risk (1 chance in 2,700) that it will collide with Earth in 2182, which would have a catastrophic impact. Better understanding its composition might therefore prove useful. Last year, NASA managed to deflect the trajectory of an asteroid by hitting it.
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