The anticipated return of the OSIRIS-REx mission to Earth

After a journey that took only 7 years, the capsule will return to our planet. It does not return home alone, but carrying samples from Bennu, an asteroid orbiting about 85 million kilometers from Earth.

This isn’t the first mission to asteroids – there was Hayabusa-1 to Itokawa and Hayabusa-2 to Ryugu – but what’s different is that this is its primary mission. OSIRIS-REx should bring back the best samples, a collection of dust grains that best represents this asteroid.

Dust to understand the formation of the Earth and our solar system

So, for two years, the capsule orbited around, taking pictures. Then she opened a 3-meter-long telescopic arm, at the end of which was the harvesting drum. I slowly descended to the surface. Finally, it fired a jet of nitrogen to blow up the dust and collect about 200 grams of the asteroid. These samples will allow us to answer big questions about the formation of our planet and our solar system.

Patrick Michel He is one of the investigators on this mission and publishes an account of his adventures “Asteroid Encounter” by Odile Jacob will be released on October 11 : “First of all, this is the initial composition of the solar system before the planets formed. The planets have a composition that evolved over time because the material they formed was heated, and thus chemically transformed, like a cake being put in the oven. Originally, this material was Those small asteroids, which, unlike planets, have not grown enough to produce these heating processes, so they have retained the memory of the initial ingredients that formed the planets. So they allow us to go back in time. Then there is the emergence of life on Earth. The asteroid Bennu was chosen based on Observations from Earth because it is believed to be rich in carbon, organic materials and aquatic minerals, including water. Therefore, we are trying to understand whether these asteroids were able to provide the ingredients that allowed life to appear on Earth at the end of the Earth’s formation when it was exposed to many impacts. »

A mission full of surprises and 13 minutes to complete

First, Bennu’s surface is rockier than one might imagine, so getting close to the surface was a challenge. Especially since it’s also softer than expected, as if the asteroid’s grains weren’t really welded together.

We still don’t know how to fully explain it, but this is what made it possible to collect so much dust… 200 grams, for a target of 60. The next challenge now, and the main challenge, is to get back to our target. Planet and The whole thing will be played out in 13 minutes long.

Patrick Michel: “The capsule is designed to rise to maximum speed in the atmosphere, and it will heat up significantly at a certain angle, so there is a lot of precision that has to be achieved to make sure we deploy the capsule on a good trajectory so it can re-enter the atmosphere. Once it reaches the atmosphere, there is no There’s still a first parachute that has to open, and then a second parachute that’s a little bit lower, because obviously we have to slow it down so you can land in the Utah desert. And from there you have to move fairly quickly to make sure the samples aren’t contaminated. And there were a lot of drills that the team did. “In charge of this operation in the Utah desert. This capsule has to be transported, first by helicopter to a nearby military center, to be protected in a preservation center. And then by plane to Houston to be able to start doing all the processing to be able to distribute the samples to the team.”

These samples will then be distributed to a whole host of scientific teams, including a small part – Cocurico – in France. Some of the grains will be received in October at the Côte d’Azur Observatory in Nice. But the bulk, roughly three-quarters, will be preserved for international distribution later and for future generations of cosmochemists, waiting for our instruments to improve in accuracy and performance. Thus, if this task is completed, it will keep many scientists occupied for decades.