To stop Apophis: experts choose the strategy of saving the Earth from asteroid collision

If the Land in the foreseeable future will be threatened by a collision with a large asteroid, how will humanity be able to prevent a cosmic disaster? In a new study published in the journal Acta Astronautica, the scientists suggested a number of ways and came up with an algorithm that will tell you which one is the best.

the Danger that may carry for the planet, an asteroid, more than real. So, in April 2029, with the Ground closer to 300-meter asteroid Apophis. He will not face the planet, but crosses the orbits of geostationary satellites. That is, will pass very close to Earth. New accord with to have Apophis in 2036. Today it is believed that it will not end with the fall of a giant celestial body, although some experts do not exclude that possibility.

Recall that this object was opened only in 2004. The reason is quite simple: asteroids are difficult to observe. On a cosmic scale, they are small and usually also poorly reflect the sunlight. So, despite all the efforts of astronomers to recalculate the Earth-threatening bodies, at any moment you can expect new surprises.

besides, it is not always easy to understand if one or another object. The asteroid may not strike during the next closer, but fall in a gravitational keyhole (gravitational keyhole). This tiny region of space where the gravity of the planet so it changes the trajectory of the guest that it leads to a clash at next rendezvous.

“Keyhole-like door as soon as it opens, an asteroid will hit the Earth quickly and with a high probability,” explains first author sung-Baek (Sung Paek) from the Massachusetts Institute of technology.

the Uncertainty surrounding Apophis was due to the fact that astronomers were hard to figure out if he gets in 2029 in this keyhole, leading to a catastrophe in 2036. Most of the potentially hazardous objects the location of these “points of death” pOprescu unknown.

What humanity will do if it becomes clear that a large asteroid some time to collide with our planet? In a report to NASA in 2007, presented to the U.S. Congress, the best option was declared the destruction of a celestial body with the help of a nuclear explosion. But in this case, the Land still falls to a hail of fragments of “alien”. If they are small enough then most will burn up in the atmosphere. However, some experts criticize this scenario, because nobody can predict what will be the consequences of this explosion and where will fall down in the atmosphere part.

Peck and his colleagues examined another opportunity. They offer to hit the asteroid hard and fast projectile on the principle of a Cannonball. It is hoped that this “kick” will push the object from the dangerous course.

“the Basic physical principle is like a game of Billiards,” says Peck.

However, this mission was a success, it is necessary to know the mass of the “heavenly stone”, its speed, trajectory and strength of rocks composing it. In this regard, it may be useful to first launch a research probe, which will study a celestial body, and then to proceed with the action.

If time allows, then, according to the experts, is to conduct a dress rehearsal. After the probe scout will collect all the necessary data and scientists will calculate the required characteristics of the projectile, you will need to run a smaller version of the latter. A small kernel will have to slightly change the orbit of the object so that experts could verify that he responds to the effect exactly as expected. You can then start the operation to save Earth.

Which of the three scenarios to prefer to beat the intruder at once, first start to it research or probe start and probe, and ensnared? In their work, scientists give humanity a tool for making such decisions.

the program uses methods Mattematicheskoi statistics and genetic algorithms to select the optimal strategy. Input data are the known parameters of the asteroid (mass, speed, and so on), location of the keyhole, the time to X hours, and the accuracy with which measured all these values.

the Authors emphasize that their method takes into account errors in the source data, because they ultimately depend on the likelihood of success of the mission. Scientists say that so far this aspect has escaped the attention of experts.

the Peck and colleagues believe that the impact on the asteroid is necessary before it will pass through the keyhole, and take on a collision course with Earth. This approach differs from the majority of scenarios in which to save the planet offers after playing “point of death”.

the Authors tested their method on data about Apophis and Bennu. This is one of the few asteroids for which we know the position of the keyhole.

the Calculations showed that if before the arrival of Apophis into the keyhole remains five or more years, then the optimal scenario with two pre-launches. If X hours from two to five years, at the rehearsal for the orbit changes in no time, but still better to send a research probe. If Apophis will enter the keyhole in the next two years, it remains at once to send to meet him, “Cannonball” and hope that everything will work out. If it passes the “point of death” in the coming year, even shock, the probe will not have time to get to it. Then you have to attack threat the lump after she takes on a collision course.

With Benn, all about the same, but it has much more data due to the fact that its orbit is now working probe OSIRIS-REx.

In the future, the authors intend to apply their methodology to assess other scenarios of defence. For example, to influence the asteroid is not one big shock probe, and several small. As such you can also try to use the satelliteand, already in orbit.

By the way, before “News.Science” ( wrote about the testing of the warning system on the approximation of the “heavenly stone”. We also talked about the first mission to change orbit of the asteroid.

Text: To.Science