What on earth are they going to do on these asteroids?

This fall, two space exploration missions devoted to the study of asteroids will get into the heart of the matter: the Japanese Hayabusa2, and the American OSIRIS-REx. As French and German partners of the Japanese space agency Jaxa, in the absence of European mission, they are about to try to put their MASCOT lander on the surface of the aircraft. one of those little bodies named Ryugu. But why is there so much interest for these big rocks in the solar system?

first, because, like comets, like 67P / Churyumov-Gerbadimenko, visited by the Rosetta probe, these objects are considered primitives capable of shedding light on the formation of our solar system. "Precisely on its origin and its evolution", explains Antonella Barucci, astronomer at the Observatory of Paris-Meudon and member of the two missions. "The difference is that asteroids formed as comets in the inner solar system are born much further from our star. So even though there has been little exchange of materials and we tend to make less and less distinction, this little body tells the same story from a very different point of view, "she adds. . "Asteroids tell us more about the formation of Earth and planets similar to Earth as comets. This is particularly interesting, "said Patrick Michel of the Observatory of the French Riviera, also a member of two missions.

In reality, asteroids evolving mainly between the orbits of Mars and Jupiter are even what scientists call planetesimals. That is, the types of bricks from which the planets were formed. They simply did not succeed in badembling to form because of the gravitational influence of the two already formed planets.

History of Water and Carbon

The second point of interest, and not least, is that asteroids can also teach us something about the origin of life. "In fact, one of the proposed scenarios for the appearance of the living is that the ingredients that allowed its appearance, namely water and organic matter, were brought to Earth by asteroids during an intense bombardment. "Says the astrophysicist. "We used to think that water was brought by comets, but when we looked at a key-marker to determine its origin, namely the deuterium / hydrogen ratio, we found that the comet was almost always different . from that of the Earth. The water on the surface of our planet could not come from it, "explains Antonella Barucci. "On the other hand, the carbonaceous chondrite type meteorites – that we find on Earth and that the vast majority of asteroids have exactly the same ratio of deuterium to hydrogen as water of our oceans and our rivers. "It means that the precious liquid may have been provided by them. And that's not all! Because the chondrites in question are derived mainly from so-called type C asteroids, such as carbon. However, that says carbon says carbon. And who said carbon is getting closer to the chemistry of life. In fact, all life as we know it is based on the atom whose ability to bind to other elements, in many ways, is the most remarkable chemical building block of the universe. From there to imagine that these asteroids have also been able to make on Earth all or part of the constituent elements of life, so there is only one step.

sample Return

"This is the reason why we have to bring back samples of these asteroids to badyze on Earth [much more finely than would the more talented of the robots posed to their area, editor’s NOTE] and this is precisely the main objective of the Hayabusa2 and OSIRIS REx missions, which are all the two stakeholders at the meeting of potentially rich carbon asteroids: Ryugu and Bennu ", explains Patrick Michel. The Hayabusa2 mission is to make three samples and plans to add a total of 0.1 to 1 gram of material. "Which can already allow multiple badyzes and bring us a lot of information," Antonella Barucci swears. As for NASA, even more ambitious, it is based on the collection of 60 grams to 2 kilograms in one point.

But is there any way to talk about organic matter when talking about water? "Yes, consider the scientist. Because there are two forms of amino acid mirrors, since you have the left hand and the right hand. This property which derives simply from the shape of the molecule [that is related to the plasticity of the carbon atom mentioned above, editor’s NOTE] is called chirality. A priori, the two forms exist in equal amounts in nature, except that, without knowing why, the proteins of living beings, they contain a majority of "left hands". "By studying the composition of the Ryugu and Bennu asteroids, the researchers hope to be able to determine whether the organic matter of these asteroids has the same characteristics as the constitutive elements of life.

Beyond Science

But scientists are not alone in paying close attention to the physical properties and chemical composition of these small bodies. "Other communities need the same information for different reasons," notes Patrick Michel. In fact, in a planetary defense goal, in the event of an announced impact with an asteroid, specialists must learn more about the enemy to develop their response. More than an attempt to destroy the asteroid by taking the risk of coping with the multiple impacts of the drifting of the biggest songs of its dislocation, the first proposed solution is to divert it. "Except that it obviously does not have to exert the same force to deflect a metal bar and sponge …" says the French researcher who pleads for a test of the deformation of the asteroid as well. a complete inventory of neas (those whose orbit crosses the one of the Earth) of at least 100 meters in diameter. "Because if the fall of an asteroid is a natural disaster, the less likely it is, it is also the only one that we can predict and avoid … provided we give the means. "

Thus, by studying the morphology of craters on the surface of Ryugu and Bennu, photographed by the probe, will global security professionals have the opportunity to better understand how these bodies react to impacts? . Data that is not without interest for a last category of actors: companies or even whole countries, such as Luxembourg – which made it a national policy – or the United States, hope to be able to , one day, use the resources present in the asteroids. Whether it is precious metals, building materials or components for the manufacture of water, fuel or batteries for the conquest of space, researchers must identify these resources and learn about the asteroids themselves in order to determine how to exploit them.