asteroids are one of the most idiosyncratic objects in the solar system. They are often only a few hundred meters to a few kilometers in size, so much smaller than planets. You do not have to send the tail, like comets. You can't even Shine as the sun. Basically, big cracks on the piles of rubble, the applying just as much gravity, not that they fall apart. This is true at least for earth orbit crossing asteroids – and here's the next character of sounds: their orbits around the sun are changeable. Some come out of the earth pretty close, too close some. Projectiles of about a Kilometer in size hit our planet on average every one Million years, with catastrophic consequences.
time capsules from the early days of the solar system
near-Earth asteroids, popular research, therefore, are objects. "They contain original Material from the early stage of the solar system, not just converted on the planet," says Ralf Jaumann from the German center for air and space travel (DLR) in Berlin. Anyone who wants to learn more about must to explore asteroids. The results are also important to develop measures against impending collisions. "If you want to deflect such an asteroid, you need to know more about him than we do." An estimated 17,000 to near-earth asteroids there are. Currently, two are examined: "101955 Bennu" under the leadership of the US space Agency Nasa with the Mission "Osiris-Rex" as well as "162173 Ryugu" with the Mission "Hayabusa 2" under the auspices of the Japanese Agency Jaxa. At a conference in Houston and at the same time in a number of journals (such as "Nature" and "Science") were presented on Tuesday, the most important intermediate results.
the highlight of The missions is to take samples from Bennu and Ryugu and to bring to the earth. It is an undertaking in which much can go wrong. At least the first use of "asteroid vacuum cleaner" of Hayabusa 2 about four weeks ago, has folded. If the second is successful, and the Material arrives safely to the earth.
The close-up, the researchers now show for both objects a surprisingly varied surface with craters and blocks, some several dozen feet tall, as well as information on Landslides. This is surprising, when one remembers that about Ryugu has only a 66.500 stel of the attraction of the earth.
Two celestial bodies, with a wasp-waist
it is Noteworthy that both asteroids cone-shaped peaks at the poles as well as a distinctive bulge at the Equator. The researchers argue that Bennu and Ryugu must have rotated once in the past faster and faster around its own axis, whereby the centrifugal force was formed following the circumferential bulge. This went easier, because the interior of the body cohesion is rather weak. They do not consist of compact Rock, but made of countless chunks that contain a lot of carbon, and the priority of the low gravity. The density was determined for both the body of 1.19 grams per cubic centimeter. For comparison: water has 1,0, ordinary Rock, 2.7, and more. The asteroids are very porous, you may have previously contained once of ice, the ice vaporized, and holes left behind, speculated the Hayabusa Team.
"We see once more confirms the theory that asteroids are a pile of this order of magnitude ultimately of rubble," says DLR researcher Jaumann, who is involved in the Hayabusa Mission. Open to whether Ryugu from the beginning existed in this size, or whether it emerged from the collision of a larger body. "I'm surprised the surface is only around a Million years old," adds the researcher. "In the scales of the solar system is nothing." Earlier, it had been thought that the body form and flying around and then over millions or even billions of years unaffected. "On the basis of the impact crater and other changes on the surface, we see that, at least, Ryugu has experienced some up in the recent past."
surveying, drilling, Shooting, Collection
The study of two body – Bennu has a diameter of about 500 meters, Ryugu around 1000 meters – is likely to deliver more Surprises. In the autumn of 2018 were sold in the frame of the Hayabusa Mission, two Rovers, and the DLR-Lander "Mascot" on the surface, to measure temperature, thermal radiation, magnetic field and other material properties; the evaluation is still ongoing. Great hopes, the researchers rely on samples to be analyzed in laboratories on earth. The probe Hayabusa has 21 on. February the surface is approached, a five grams of light-weight projectile fired into the air and swirling dust in a sample container collected. In April, a 2.5-Kilo should be shot-the projectile, the Material from the deeper layers out of the hurl, not affected by space weathering. This is supposed to float, thanks to the low gravity, on the surface, and days later, with a gripper arm is to be collected. The end of the year, the probe has to fly back to earth, where they the end of 2020, it is expected.
So exciting this sounds endeavor, things can go wrong, like the previous mission. When you approach the asteroid "Itokawa" in 2005, the Hayabusa-1 had gone into a safety mode and had rather collected randomly, some of the granules came back because of technical problems with the probe only in the year 2010 on earth. Now, the yield will be somewhat more extensive and faster to the lab.
mining-euphoria is gone
the Nasa Team has been provided with the Osiris-Rex sampling, however, until July 2020, when one is very sure where is the best place for it. A meter-long boom to at least collect 60 grams of Material. The technology could one day also for the space-mining is interesting. The scientific head of the Osiris-Rex Mission, Dante Lauretta, is also want to the scientific Advisory Board of the company Planetary Resources, the raw materials on other heavenly bodies win. However, the initial euphoria is gone. Planetary Resources got into economic difficulties and had to cut jobs, reported the magazine "Fortune" in November. Lauretta told the magazine that he cannot help thinking that all the problems of asteroid mining are, in principle, solvable. But he has not spoken now that it could go in the next decade, but announced it now to a project that would require several decades.
A similar time, you will need to plan for a need for methods for asteroid defense. To edit a collision candidate with nuclear warheads is pointless, says Jaumann. "Instead of a large body of many small flying around then." The better method is to affect the orbit of the asteroid, to distract him. "I need to know, however, how big is its density, how the internal structure is, how the composition is." Then we could decide whether it was better to slow down the Rotation, which also affects the price, or an awning attached, or with a space ship to dock, and economical ion engines to leave the factory for a long time in a certain direction. "Long impact slide in any case, than to give a short pulse," says Jaumann. Although Bennu and Ryugu not be considered as near-earth asteroids, impact risk of one of them, however, is convinced of the researchers.
This could be the case for some other of the 17 million but quite real. "Especially since we know about the body, which are smaller than a Kilometer, very little. These can also have an impact at least at the regional serious consequences,“ the scientists ' concerns. "One is well advised, if one is prepared for such things."