Experts choose a strategy to save Earth from an asteroid impact

Experts choose a strategy to save Earth from an asteroid impact
Experts choose a strategy to save Earth from an asteroid impact
Anonim

If the Earth is threatened by a collision with a large asteroid in the foreseeable future, how can humanity prevent a cosmic catastrophe? In a new study published in the journal Acta Astronautica, scientists have proposed several methods and come up with an algorithm that will tell you which one is the best.

The danger that an asteroid can carry for our planet is more than real. So, in April 2029, the 300-meter asteroid Apophis will approach the Earth. It will not collide with a planet, but it will cross the orbits of geostationary satellites. That is, it will pass very close to the Earth. A new rapprochement with Apophis is expected in 2036. Today, it is believed that it will not end with the fall of a giant celestial body, although for some time experts did not exclude such a possibility.

Let us remind you that this facility was opened only in 2004. The explanation is quite simple: asteroids are difficult to observe. By cosmic standards, they are small and, moreover, usually reflect sunlight poorly. So, despite all the efforts of astronomers to recount the bodies threatening the Earth, new unpleasant surprises can be expected at any moment.

In addition, it is not always easy to understand whether a particular object is dangerous. The asteroid may not strike at the next approach, but fall into the gravitational keyhole. This is a tiny region of space in which the gravity of our planet changes the trajectory of a guest so much that it leads to a collision at the next rendezvous.

"The keyhole is like a door: once it opens, the asteroid will hit the Earth quickly enough and with a high probability," explains the first author of the article, Sung Paek of the Massachusetts Institute of Technology.

The uncertainty around Apophis stemmed from the fact that astronomers had a hard time figuring out whether he would fall into such a keyhole in 2029, leading to disaster in 2036. Moreover, for the majority of potentially dangerous objects, the location of these "points of death" is simply unknown.

What will humanity do if it becomes clear that a large asteroid will collide with our planet after a while? In a report that NASA presented to the US Congress in 2007, the best option was declared the destruction of a celestial body with a nuclear explosion. But in this case, a hail of fragments of the "alien" will still fall on the Earth. If they are small enough, they will mostly burn up in the atmosphere. Nevertheless, a number of experts criticize this scenario, because no one will be able to predict for sure what the consequences of such an explosion will be and where the parts not burnt in the atmosphere will fall.

Peck and his colleagues were considering another option. They propose to hit the asteroid with a heavy and fast projectile on the principle of a cannonball. It is assumed that such a "kick" will push the object off the dangerous course.

"The basic physics principle is like a game of billiards," Peck says.

However, for such a mission to be crowned with success, it is necessary to know as accurately as possible the mass of the "heavenly stone", its speed, trajectory and strength of its constituent rocks. In this regard, it may be useful to first launch a research probe that will study a celestial body, and only then proceed to active actions.

If time permits, then, according to experts, it is worth holding a kind of dress rehearsal. After the "scout" probe has collected all the necessary data and the scientists have calculated the required characteristics of the projectile, it will be necessary to launch a smaller version of the latter. The small core will have to slightly change the object's orbit so that experts can verify that it responds to the stimulus exactly as expected. After that, it will be possible to begin the operation to save the Earth.

Which of the three scenarios do you prefer: hit the intruder at once, first launch a research probe towards him, or launch both the probe and the minishot? In their work, scientists provide humanity with a tool for making such decisions.

Their program uses methods of mathematical statistics and genetic algorithms to select the optimal strategy. The input data for it are the known parameters of the asteroid (mass, velocity, and so on), the location of its keyhole, the time margin of up to an hour X, as well as the accuracy with which all these quantities were measured.

The authors emphasize that their methodology takes into account errors in the initial data, because the probability of the mission's success ultimately depends on them. Scientists say that until now this aspect has escaped the attention of specialists.

At the same time, Peck and colleagues believe that it is necessary to influence the asteroid before it passes the keyhole and sets the course for a collision with the Earth. This is how their approach differs from most scenarios in which it is proposed to save the planet after passing the "point of death".

The authors tested their method on data on Apophis and Bennu. They are one of the few asteroids for which the position of the keyhole is known.

Calculations have shown that if there are five or more years left before Apophis enters the keyhole, then the scenario with two preliminary launches is optimal. If up to hour X is from two to five years, then there is no time to rehearse the orbit change, but it is still better to send a research probe. If Apophis enters the keyhole in the next two years, then it remains to immediately send him a "cannonball" and hope that everything will work out. If he passes the "death point" in the next year, then even the impact probe will not have time to reach him. Then you will have to attack a dangerous block after it takes a collision course.

With Bennu, everything is about the same, but there is much more data about him due to the fact that the OSIRIS-REx probe is currently operating in his orbit.

In the future, the authors are going to apply their methodology to assess other defense scenarios. For example, an asteroid can be influenced not by one large impact probe, but by several small ones. As such, you can also try to use satellites already in orbit.

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