The Osiris-Rex probe brings back to Earth small samples from the asteroid Bennu, a “real small world” to analyze

This is a very rare gift, which must literally fall from the sky on Sunday September 24. Samples taken three years ago from an asteroid, hundreds of millions of kilometers from us, will be recovered after being reported by the American Osiris-Rex probe. After a long journey, the probe will drop its precious cargo, more than 100,000 kilometers above our heads. The analysis should help us learn more about the origins of the solar system.

>> Osiris-Rex mission: “What is at stake is understanding the origin of life”, deciphers astrophysicist Antonella Barucci

In the capsule which must be received are a few hundred grams of precious fragments of rock and dust collected from the asteroid called Bennu. It will leave the Osiris-Rex probe to begin a long descent through space and then the Earth’s atmosphere, before landing in a secure area of ​​the Utah desert, in the west of the UNITED STATES. After cleaning the capsule, the samples will “be sent to Houston, to the NASA Johnson Space Center”, explains Bernard Marty, professor of geochemistry at the University of Lorraine. “There, the capsule will be opened and the scientists will look at what is inside.”

The time will then come to send some of these samples to selected laboratories around the world, by simple carrier. For Bernard Marty’s Nancy Petrographic and Geochemical Research Center (CRPG), specialized in the analysis of rare gases, the package will contain a few milligrams of these asteroid extracts. “We will open these sealed boxes under a flow of nitrogen and we will introduce our samples into rooms where they are analyzed. These are rooms with a window where they will be heated with lasers”, explains the specialist in rare gas analysis. It is during this heating that “gaseous species will be released”allowing their analysis with mass spectrometers.

Learn more about the origin of our planets

Thanks to this, researchers will know the chemical composition of these samples. Enough to learn more about the ingredients at the origin of our planets. Asteroids are considered early fossils, containing the “fundamental building blocks” which allowed us, four and a half billion years ago, to gradually build our solar system. And above all, they contain the “bricks” which gave rise to life. The first sample analysis results are expected in the coming months. Part of this extra-terrestrial matter will be preciously preserved in the UNITED STATES, while waiting for new technologies to appear, allowing, we hope, analyzes that are still impossible today.

This return of samples is a major step in an extraordinary journey, which has already brought its share of knowledge. Launched in 2016, the Osiris-Rex probe was placed in orbit around Bennu at the end of 2018, somewhere in the asteroid belt between Mars and Jupiter. Before collecting samples from this asteroid, approximately 500 meters in diameter, scientists studied it. This is the case of Patrick Michel, research director at the CNRS at the Côte d’Azur Observatory, and co-investigator of this Osiris-Rex mission: “We learned that when we look at them with a space probe at very close proximity – that is to say we resolve them, we make images of them – these objects are much more complex and fascinating than when we look at them through ‘a telescope by collecting only the light they reflect from the Sun.’ For example, scientists have found “the incredible abundance of rocks” on the surface of Bennu, “a body that is barely 500 meters in diameter and has very little gravity.”

“We have an incredible variety of geological structures, continues Patrick Michel about Bennu. It undergoes various processes: we see avalanches, surface movements, cracks on the rocks which indicate to us that it has undergone thermal fatigue, impacts, craters… It’s quite fascinating, these are real little worlds.”

There was also this day in October 2020 when, like a mosquito, the probe came to prick the surface of the asteroid, to collect a few grams, under the enchanted and misty eyes of the NASA teams . It was the first time that the American agency attempted this very complex maneuver, which only a Japanese mission had succeeded on another asteroid, a year earlier.

The Osiris-Rex probe has not finished with space, since as soon as its sample capsule has been released, it will head towards another asteroid, named Apophis, which must pass very close to the Earth. The meeting is scheduled for 2029.