The feature of the surface of the asteroid Ryugu jeopardizes the mission of the Japanese probe

Discovered feature of the surface of the asteroid Ryugu casts doubt on success of mission of the Japanese space probe “Hayabusa-2”, whose main purpose is to collect samples of soil. We have previously reported that the surface of the asteroid successfully landed two Japanese Rover, and the German lander. And while the world celebrated the first photos of the surface of the Ryuga, Japanese scientists were shocked of what we saw in those pictures.

On the first results of work on the asteroid’s surface Ryugu at the DPS conference, held in the U.S. city of Knoxville, shared Masaki Fujimoto, one of the leaders of the mission “Hayabusa-2”, as well as other members of the mission.

“Obtained the first pictures of an asteroid literally plunged us into shock. We expected that these images will help us to expedite the preparation and procedure of planting and subsequent soil sampling. But it was quite the opposite. After seeing the data, we realized that we have big problems to solve that just won’t work,” says Fujimoto.

Recall that the space probe “Hayabusa-2” was launched in December 2014. Its main task is to collect soil samples of the surface of the asteroid Ryugu and send these samples back to Earth. The asteroid surface is planned to fire explosive projectile onboard “Hayabusa-2”, and the resulting explosion of the particle surface to collect in the container and after a couple of years to lose on the Ground.

At the end of September on the surface of the asteroid was successfully reset and successfully planted two Japanese hopping Rover MINERVA-II1. In early October, the probe also dropped on the surface of the Ryugu German lander MASCOT. The latter worked on the surface in just 18 hours (as planned).

Initial training to the main part of the mission – the “shot” of the asteroid was to begin in October, however, the Japanese space Agency JAXA and its partners involved in this mission, had to postpone these plans until at least early January.

“When learning something new and unknown, we usually try to rely on past experience. In this case, this experience played with us a cruel joke – asteroid, Itokawa, which we examined in the framework of the mission “Hayabusa-1″, was quite unlike the Ryuga. But we have, and we will have to solve any unexpected problems,” explains Fujimoto.

The first bell of the approaching problem sounded when approaching probe “Hayabusa-2” to the asteroid in late summer. The camera took a few pictures of its surface, where scientists observed a large cluster of boulders. The surface it turned out there was literally littered with them.

“We are very much mistaken in my calculations. Now it’s hard to say why we believe that the surface of the Ryuga is covered with a uniform layer of regolith, as Itokawa. On the other hand, it is clear why the error occurred — all the other comets and asteroids is also similar to Itokawa in this respect,” continues the scientist.

Strewn with boulders the height of from several tens centimeters to several meters of surface Ryugu difficult choice of land for planting. No, put the probe “Hayabusa-2” directly on the surface of the asteroid scientists are not going, but want to bring it with surface, to shooting him and collecting samples. This requirement is caused by the absence of the probe’s robotic arm, which can be collected has risen after the explosion particles.

The main difficulty, as scholars have noted, is how to bring the apparatus to the minimum distance with the Ryuga, and then dropping explosive shells, shoot him a kind of “bullet” in the moment of contact with the surface. After that, the device needs to gain altitude and make a few turns around the Ryuga, collecting dust and small stones, thrown into the space above the surface of the asteroid, with the help of special traps. Scientists initially hoped in this way to several tens of grams of regolith, but at the moment the prospects of this venture are unclear.

Lucille Le Corre, one of the participants of the mission of the Planetological Institute in Tucson (USA) explains that such demands for “Hayabusa-2” and the feature surface, the Ryuga is significantly complicated the selection of the landing site of two Rovers of Japanese, as well as tasks for collection of soil. Scientists eventually chose three potential landing point (L07, L08 and M04), located near the equator of the asteroid, but here, not everything was so simple as we would like.

Yes, each point has some seats available for the landing, each with an area of 100 x 100 meters. But they contain dozens of large stones that could lead to the failure of the mission during the bombardment of the surface and subsequent overflights of the probe around the asteroid to collect samples.

“We essentially only get one shot in order to obtain soil samples from the inner layers of the asteroid. Onboard “Hayabusa-2” there is only one firecracker and attached the 2.5-pound copper “bomb”, and a small number of tantalum bullets. If something goes wrong, other opportunities, we will not,” adds Fujimoto.

The researchers note that it was originally planned to conduct a trial soil sampling in October of this year, and the bombing in March-April next. But the opened parts of its surface has led scientists to push back these plans at a later date.

His caution researchers due to the fact that they do not fully know the structural features of the asteroid, and did not understand why on the surface there is a huge number of stones. If it’s not to find out further mindless continuation of the mission may lead to its catastrophic failure. For example, if you plow up, can raise a large number of stones that can damage the probe.

“To date, we have had several guesses, but previously received data is already hinting that Rugu represents not a monolithic body but a kind of “hodgepodge” of many large stones and other natural objects of space debris. The asteroid could appear in the result of collision of two other objects, consisting of a relatively soft and fragile matter,” the scientists explain.

According to the assumptions of Le Offset, strewn with boulders, the surface can be explained by the following analogy. If you take a bag, fill it with small stones and large boulders, and then well shaken, then large stones would be on the surface but small pellets Scopata on the bottom of the bag. If the assumption is true for the Ryuga, it could mean that its surface is constantly updated with new stones that also will need to consider during the mission, collecting samples. Currently, the team verifies this guess by comparing pictures of the asteroid and spectroscopic data that show the calculation results of computer models Ryugu.

But can it be as serious as it is imagined by scientists from the Japanese space Agency? According to Ralph Jaumann, project Manager of the MASCOT of the German space Agency (DLR), he suggests that the impact of boulders on the probe “Hayabusa-2” may not be as catastrophic as it seems his colleagues.

“During the landing on the asteroid, our module ran into one of these stones and fell to his side. Fortunately, nothing terrible happened. We expected that something like this could happen. Moreover, this clash has helped us to carry out measurements that clarified the properties of matter of the asteroid,” — says the scientist.

Aumann, notes that the scientists of the mission perfectly represented, what is the kinetic energy possessed MASCOT during this collision. These data allowed them to calculate the density of the stone, leaning on his photographs taken after the lander made the next jump.

Scientists have found that the matter of the stone was very soft and porous. Therefore, the collision module with it rather caused damage to the cobbles, not the module. The stone is deformed and partially collapsed. On its surface left a big dent. German scientists believe that the density of matter is characteristic of the asteroid.

Find out for sure the mission team plans to help the analysis of more than hundreds of photos and data collected by MASCOT and information that will be collected by one of the Japanese jumping Rovers, who continue to work on the asteroid’s surface. In addition, to minimize the risk of landing, according to the researchers, could be due to the maximum precision of the execution of this process. And on this mission, engineers are already working. For example, scientists want to reduce the size of the landing probes to a size of 20 meters. It is noted that accurate positioning to date has already reached the level of 10.8 meters, which should already be enough for accurate touch the surface. In addition, the “Hayabusa-2” were spread on the surface of the Ryugu special beacons that help the machine to calculate the correct position while reducing the area M04. At the moment it is considered by experts the most secure JAXA for such an operation.

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