[update Friday, 22]. It is a historical fact. The probe of the japanese space Agency (JAXA) Hayabusa2 has managed, in the night of Thursday 21 to Friday 22 around midnight, to ask a few seconds to the surface of the asteroid, Ryugu, located 300 million miles from Earth. During this brief contact, the japanese spacecraft has had time to launch a projectile, a kind of ball – against the surface to create a crater artificial, and generate a few milligrams of dust extra-terrestrial, she sucked using her “wrong”. First anxiety, the officials of the mission have left their joy burst when they have received the first positive signals. The scene live from the control room, was broadcast live on Youtube (review below from 1: 20) :

“The operation of landing and harvest sample is a total success ! This is a great step in the history of space exploration, ” says Patrick Michel, director of research at the CNRS at the Observatoire de la Côte d’azur (OCA) and a member of the scientific team of the project japanese. And yet, the maneuver was far from obvious. “The probe has taken a day and to descend from its orbit (at 20 km altitude of Ryugu) up to the surface to aim a zone of six metres wide only,” continues the French researcher. And for good reason, the study of the asteroid about 875 metres in diameter, led by Hayabusa2 since June 2018, revealed a surface that is much more rocky than expected, with some blocks in excess of 10 meters in height. Find an area that is sufficiently planar to allow a “touch-down” (touch and bounce) without risk has, therefore, been a real headache for researchers.

“I’m a fan of Hayabusa2, because this mission is very ambitious, as the Japanese like to do, added the French scientist, only non-japanese present in the control room, during a press conference given on the spot. She has performed many “first”: the first detailed map of an asteroid potentially rich in precious materials, the first deployment of the robot to the surface of such a star [two small rovers sautillants are laid on the surface of Ryugu in September 2019, as well as the robot-German-French Mascot, on 3 October], and the first collection”. All while the project has cost $ 300 million, “only”, compared to a billion for OSIRIS-REx, the american mission, which aims to harvest from 55 grams to 2 kilograms of rocks and dust on the surface of the asteroid Bennu.

Back on Earth in 2020

the origin of the mission, two other attempts to recover samples were planned. But after the analysis of the dangerous surface of the asteroid, only the second will be maintained. The final purpose of Hayabusa2 is to report samples of Ryugu on Earth by 2020. “Once on Earth, this precious cargo will carry out analysis to be extremely detailed in conditions that no space probe can perform, gives details of Patrick Michel. Without account the cost of instruments placed in orbit, is 10 to 100 times higher than a terrestrial laboratory then they are 1000 times less accurate.” And between the time necessary for the design of the spacecraft, its launch and the start of the mission, the instruments it uses may be out of date compared to those developed on Earth. Another advantage of bringing a extracts asteroid down here is that 70% of the sample is preserved for future generations.

Studying asteroids is of paramount importance to more than one title. From a purely scientific point of view, the heavenly bodies, composed of the same basic elements as the planets, may help us to better understand how the solar System formed and then developed. The latter has emerged 4.6 billion years ago, when an enormous nebula made up of gas and dust collapsed under its own weight. A few tens of million years later, the Sun is switched on for the first time. The dust grains swirling around him have started to collide and aggregate, and then turned into little pebbles, asteroids and finally into moons and planets, including the Earth. In their environment, frozen, asteroids have been generally preserved, and therefore represent a kind of museum space, the “elementary bricks” witnesses of a bygone era. The ultimate purpose of Hayabusa2 is to contribute to enrich the knowledge of our space environment “to better understand the emergence of life on Earth,” says the responsible of the Jaxa.

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But the asteroids, especially neas as Ryugu – those whose orbit crosses that of Earth, and are therefore potentially dangerous – were also of concern to the authorities in charge of planetary defense. If the impacts of the most violent ones are extremely rare (see infographic below), the fall of a meteorite to a dozen meters in diameter on Earth, which occurs approximately every five years -, causes an explosion equivalent to 5 Hiroshima bombs. A better understanding of the gravity of the asteroids, their composition and the factors that may affect their trajectory is, therefore, essential to provide a means of deflecting or destroying a threatening object. Don’t panic, however, Ryugu (875 metres) has almost no chance of us crashing in front of several thousands of years.

“Hunt down the dangerous asteroids”. DIAMETER AND FREQUENCY Of the IMPACT : 1 meter (all years) ; 10 m (every 10 years) ; 100 m (every 1000 years), 1000 m (all the 500 000 to 1 million years), more than 1 Km (every 1 in 300 million years). POWER Of EXPLOSION (equivalent to megatons of TNT) : the atomic bombing of Hiroshima (15 kilotons) ; asteroid of Chelyabinsk (17 to 20 meters in diameter, 0.5 Mt) ; Toungouska (30 – 40 m, 3 to 10 Mt) ; The bomb Czar (more powerful atomic bombs, 50 Mt) ; Apophis (325 m, 750 Mt) ; Chicxulub (the asteroid that eradicated the dinosaurs, 65 million years ago, 10 to 15 km, 100 million Mt). NUMBER Of ASTEROIDS ESTIMATED : 0 to 30 meter : 3550 discovered on 4 million. 30 to 100 m : 5212 1 million. 100 to 300 m : 4552 30 000. 300 to 1000 m : 4007 on 5440, more than 1000 m : 892 on 930.


And for a few billions of billions of dollars more

“And we should not forget the industry,” notes Patrick Michel. Many of them dream to one day take ownership of the mineral resources of the objects of the asteroid belt between Mars and Jupiter. These could contain up to 700 trillion dollars (a thousand billiards), according to the us space Agency (Nasa). Ryugu, a priori rich in precious metals, could be worth alone is $ 82 billion, according to the site Asterank, which compiles the available information on these bodies and assesses their cost-effectiveness. The market, still very blur, enough to stir the envy of many entrepreneurs. Skeptical, Patrick Michel recalls that “if the precious metals are concentrated on the Earth in mines, on an asteroid they are scattered, so the business plan does not !”. The specialist is, however, more seduced by the idea of using, a day, the water and the carbon present in some of the asteroids to make fuel and oxygen, transforming the asteroids by potential service stations for the explorers of the future.

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Build a base inside an asteroid would be, on paper, technically possible. So say three astrophysicists from the university of Vienna (Austria), which recently published the first conclusions of their work. The interest of such a project ? Not only the rocky walls of the heavenly bodies could protect the occupants from radiation, the main danger for travelers in space, but their speed of rotation would create sufficient gravity to that of human beings – minors, for example – to be able to reside there without sacrificing their health. “For the moment, we don’t even know what the inside of an asteroid, as well as interact with them, digging, etc, is extremely complicated”, says Patrick Michel. It is likely to take a lot of time between theory and practice. In the meantime, it is not forbidden to dream.


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