The maneuver promises to be delicate for the probe.

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Handout / NASA / Goddard / Arizona State University / AFP

She left Earth in 2016. After four years of travel and observation, the American probe Osiris-Rex must descend this Tuesday on the surface of the asteroid Bennu to take samples of its soil, in the hope of bring back to Earth.

With the hope that these discoveries can enlighten us on the formation of the solar system.

The asteroid has been carefully chosen for this mission.

Bennu is 490 meters in diameter and its surface was believed to be covered with sand "like a beach," as scientists believed based on telescope observations, university Dante Lauretta told a conference call. from Arizona, scientific leader of the mission.

Such a surface would have guaranteed a safe sampling operation.

A touch of a few seconds

But upon arriving near the pebble in late 2018, footage showed it was actually covered in rocks.

“The surface is rough, rugged, rocky,” the scientist described.

The team spent 2019 painstakingly mapping the surface to select the most secure site for sampling: Nightingale Crater.

This Tuesday, the probe must slowly approach Bennu, then deploy a sampling arm and target an area eight meters in diameter, relatively flat, as wide as four parking spaces.

“Years of preparation and hard work by this team will boil down to this contact with the ground for five to ten seconds,” summed up Mike Moreau, deputy project manager at NASA.

Just 3 more days until I collect a sample from asteroid Bennu!

Celebrate with me and my team as we look back at all the challenges we've overcome to get to this point.

pic.twitter.com/W53NTQVpv8

- NASA's OSIRIS-REx (@OSIRISREx) October 17, 2020

For a handful of rubble

By touching the ground, the robot will blow nitrogen, which will make fly grains which will then be recovered by the arm of Osiris-Rex.

The goal is to collect at least 60 grams.

According to Mike Moreau, there is up to a 30% chance that the arm will not recover enough material, for example if the contact is on a large stone instead of finer grains.

Engineers over 320 million kilometers away cannot guarantee absolute precision.

If this attempt is inconclusive, a second could take place in January in another crater.

In March 2021, Osiris-Rex will begin its long journey back to Earth.

It will eventually release the container containing the samples for a landing in the Utah desert, slowed down by a parachute, on September 24, 2023. Before that, the Terrans prepare to analyze the samples from another asteroid, Ryugu, to which visited the Japanese probe Hayabusa 2 last year.

The return to Earth of this dust is scheduled for December 6.

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