What do we do if a “planet killer” asteroid hits Earth?

Beijing time, February 25 news, if a huge space object is looking at the Earth, what should we do? We might be able to hit it hard with a spaceship, derail it, or detonate it with a nuclear weapon; drag it with a gravitational puller; or even slow it down with focused sunlight. So which option is best? Researchers at the Massachusetts Institute of Technology calculated the problem, proposed a system to assess the final effects of these choices, and simulated two asteroids and their paths in space.

A rocket is flying too close to Earth, near a probe to detect impacts (imagine)

First, we must decide whether to carry out a reconnaissance mission first or launch an immediate and full-scale attack. The big decision, which was made under the pressure of survival, prompted the MIT team to publish a guided paper in february in the Journal of Astronautics exploring options that could deflect asteroids.

In the film, the asteroid’s impact takes place almost entirely at the last minute: a huge and deadly space rock that shoots straight into Earth like a bullet fired from the dark, only weeks or even days from the time it is discovered. According to a Report by NASA’s Planetary Defense Office in April 2019, asteroid impacts are a real threat to humanity, but at the same time, NASA believes they have found most of the largest and most deadly objects, the so-called “planetary killers”. The chanceof impact on the earth is very small. Of course, there may be a large number of small, but still large enough asteroids to destroy the entire city.

Most of the larger space objects near Earth are already under close surveillance, so we may get a lot of warningbefores before an asteroid hits Earth. Astronomers look at these space rocks near Earth to see if they could pass through a “keyhole.” Every asteroid that threatens Earth will get closer or farther from Earth at different locations around the sun’s orbit. Along this path, the so-called “keyhole” exists near the earth. If the asteroid ends up colliding the next time it approaches our planet, it will have to pass through this space region.

“The keyhole is like a door, and once opened, the asteroid will hit the Earth very quickly, with a high probability,” said Sung Wook Paek, a Samsung engineer who led the study and was a graduate student at the Massachusetts Institute of Technology. The paper points out that the easiest time to stop an object from hitting the Earth is before it passes through a “keyhole”. This will prevent the object from hitting the earth from the start. Once an asteroid crosses the “keyhole” into the orbit that strikes the Earth, it will require more resources and energy and more risk.

Sung Wook Paek and other authors abandoned most of the options for deflecting asteroids, considering only the options for nuclear explosions and impacts. Nuclear explosions, they write, are likely to pose problems, because the exact performance of asteroids after a nuclear explosion is not easy to determine, and political concerns about nuclear weapons could hamper missions.

Finally, they offered three options for deflecting asteroid missions. If a “planetary killer” asteroid is found to be flying toward a “keyhole”, these scenarios can be prepared in a short time.

(1) “Type 0” mission: is to launch a heavy impactor into the incoming target, using as much detailed information as possible about the composition and orbit of the target, to derail it;

(2) “Type 1” mission: first launch a reconnaissance device, before the main impactor launch to collect close-range data of asteroids, in order to better target the shooting, to obtain maximum effect;

(3) “Type 2” mission: a small impactor is launched at the same time as the reconnaissance, the target is slightly off track, and then, based on information from the reconnaissance and the first impactor, the second small impactor is fine-tuned so that the asteroid can not eventually pass through the “keyhole”.

The problem with the “0” mission, the researchers write, is that telescopes on Earth can only collect rough information about “planetary killer” asteroids that are still far from Earth, relatively small in size, and reflect dim light. Without accurate information about the asteroid’s mass, velocity, or physical composition, the impactor mission would have to rely on inaccurate estimates that would make it more risky not to prevent an asteroid from passing through the “keyhole”.

The researchers believe the Type 1 missions are more likely to succeed because they can more accurately determine the quality and speed of asteroids, but such missions also require more time and resources. The Type 2 task may work better, but it requires more time and resources.

The researchers developed a way to calculate which mission would work better, based on two factors: from the time the mission began to the asteroid’s arrival at the “keyhole” and the difficulty of deflecting a particular asteroid properly.

The researchers applied the results to two well-known “planetary killer” asteroids near Earth: Apophis and Bennu, and came up with a complex set of instructions. Once one of the asteroids starts moving toward the “keyhole”, the command can be used to design a probe that deflects it.

They found that if there was enough time, the Type 2 mission would almost always deflect the asteroid Benou properly. However, if the time is short, you can use the fast-track “0” mission. Only in a few cases will the Type 1 task work.

For the asteroid Aporfis, the situation is different and more complex. If time is tight, the Type 1 mission is usually the best option: collect data quickly so that it can be targeted and impacted correctly. If there is more time, the Type 2 mission is sometimes a better choice, depending on how difficult it will be for an asteroid to deviate from its course. In any case, the “Type 0” mission has no effect on Apophis.

If the time is too short, neither Apofis nor Benu can successfully deflect them. The differences between asteroids are due to uncertainty about their mass and velocity, and the reaction of their internal matter to impacts. These basic principles could also be used to study other potential “planetary killers” and future studies could combine other options to change the direction of asteroids, including nuclear weapons, the researchers wrote. The more choices you make, the more complex it becomes, the more difficult it is to calculate. The researchers concluded that training machine learning algorithms will play a greater role in the future, helping astronomers make decisions based on accurate data in scenes where asteroids hit Earth. (Any day)