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OSIRIS-REx part in the assault of the asteroid Bennu

 the OSIRIS-REx probe the Kennedy space center in Cape Canaveral (Florida), on 20 August.

NASA launches Thursday 8 September, the OSIRIS-REx probe to a large cosmic pebble 500 meters in diameter, named Bennu, whose orbit crosses that of the Earth every six years. The American machine in the footsteps of Hayabusa-2, launched in December 2014 by the Japanese JAXA towards the Ryugu asteroid.

The two missions promise a “big media show” , according to Patrick Michel, CNRS research director at the Observatoire de la Cote d’Azur, which is working with both agencies. With as highlight of the show, the return to Earth of two lots of samples of pieces of asteroids, in 2020 and 2023.

In 2010, Hayabusa-1 had already reported a few tiny crumbs of ‘Itokawa asteroid. The adventures of the two probes in contention today will therefore not be the “first”. But they are very exciting: “OSIRIS-REx will help answer three major questions that arise astrophysicists said Jeff Grossman, one of NASA scientists: better understand how solar system formed, determine how the asteroids are home to exploitable resources and finally refine plans for diverting such a star should he threaten Earth. “

The main challenge will be to harvest the material – regolith – on the surface of asteroids. The Japanese have developed a system of throwing a projectile on the surface of the star from the probe that it will be asked, the generated chips being sucked into the return capsule. OSIRIS-REx, like a hummingbird, it is “foraging” Bennu flying close to the surface. Then a sort of trompe will come into contact with the ground.

The acquisition mechanism will then suddenly spit compressed nitrogen. What lift fragments, once collected in interior curved edges of the pipe. This crop will be placed in a return capsule identical to that of the Stardust probe, which, in 2006, was brought back to Earth some dust of a comet.

60 grams of material

the value of US technology is that it should gather at least 60 grams of material, against micrograms only with Japanese device. “This will perform analysis of any organic matter structures unachievable with small amounts brought back by Hayabusa-2 said Patrick Michel. For this, it is in fact at least 10 grams of material, knowing that 75% of samples of OSIRIS-REx will be retained for further studies. “

This research will feed another field for the time yet spooky: the asteroid mining. Another track, the use of in situ resources for the exploration of the solar system. “We disassociate the molecule H 2 0 to make hydrogen (H) and oxygen (O), which become fuel Fuse e says Dante Lauretta, chief scientist of the OSIRIS-REx mission. In addition, carbonaceous asteroids are also rich in phosphorus and other elements used as fertilizer to grow food in space travel. “ The asteroids would then act as a” service station “in space.

” One of the major threats to life in the Universe is a high probability the impact of an asteroid on inhabited planets “, recently pointed out the famous astrophysicist Stephen Hawking. The risk (known) of such an event today is admittedly small, but not zero. The trajectories of small celestial objects are difficult to predict with great accuracy, because of the “Yarkovsky effect”: it is a small thrust generated through restitution in the form of infrared radiation of solar energy absorbed by the celestial body.

“Now how the characteristics and nature of an asteroid influence this effect is largely unknown , said Patrick Michel. OSIRIS-REx will learn more. On the other hand, the impactor device installed on Hayabusa-2 will, depending on the reactions of the surface of the asteroid, refine our impact models. “ If it would one day develop a parry to repel this threat from the sky.

The classification of impact risks of large body established by NASA, Bennu Figure … second. Just behind an asteroid of 1.3 kilometers in diameter – (29075) 1950 DA – which is most likely to hit the Earth in 2880. For Bennu, the “collision niche” most likely are 2175 and 2196, with a (bad) luck of about 2500 or so, according to the US space agency.

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