2023-09-22 16:15:04
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 9:00 a.m. local time (3:00 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.
Image taken by NASA’s Osiris-Rex probe on December 2, 2018, showing the asteroid Bennu
NASA/Goddard/University of Arizona/AFP/Archives
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 fall, observed by army sensors, will be slowed by two successive parachutes, allowing, if all goes well, a soft landing.
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.
Transported to Texas
“Sample return missions are difficult. A lot of things can go wrong,” warned Sandra Freund of partner company Lockheed Martin.
Sandra Freund of partner company Lockheed Martin during a NASA asteroid sample recovery rehearsal for the Osiris-Rex mission June 27, 2023 in Littleton, Colorado
AFP/Archives
The possibility of a “hard landing”, for example if the parachute does not deploy, has been prepared.
A dress rehearsal took place at the end of August, with a replica capsule dropped from a helicopter.
Once the capsule is on the ground, a team will check its condition before placing it in a net, which will be lifted by a helicopter and taken to a temporary “clean room”.
The next day, the sample will be sent on a plane to the Johnson Space Center in Houston, Texas.
The laboratory where samples from the asteroid Bennu collected by the Osiris-Rex probe will be analyzed, July 24, 2023 in Houston, Texas
AFP/Archives
This is where it will be opened, inside another airtight room. The priority is not to contaminate the sample with earth material, so as not to distort the analyses. The process will take days.
NASA is planning a press conference on October 11 to reveal initial results.
Part of the sample will be preserved for study by future generations.
250 grammes?
Osiris-Rex took off in 2016, and in 2020, the asteroid Bennu surprised scientists during the collection of the sample: during the contact of a few seconds with the surface, the arm of the probe had sunk into the soil, revealing a much lower density than expected.
Image taken from a NASA video showing the robotic arm of the Osiris-Rex space probe making contact with the asteroid Bennu to collect samples, October 21, 2020
NASA TV/AFP/Archives
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 collected sample 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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