Millions of years ago, Earth was believed to be hit by a giant asteroid making the dinosaurs to go extinct. Although there is no known imminent danger of it happening again soon, researchers from MIT led by Sung Wook Paek described a "decision map" that could help determine the best possible ways to avoid a collision.
We have few options in deflecting the asteroid-like slowing it down using concentrated sunlight, blasting it with a nuclear weapon, tug on it with a gravity tractor or to knock it off its course we can hammer it with a spacecraft.
All of those require a lot of decisions to make that is why Sung Wook Paek and his team of researchers came up with the "decision map" and published it in the Acta Astronautica journal this February in case a 'planet killer' asteroid hits Earth.
According to an April 2019 presentation by NASA's Office of Planetary Defense, those we see in movies wherein an incoming asteroid is usually detected in the last minute with all those big, deadly rocks hurtling right toward Earth like a bullet out of darkness with only a few months or weeks left may happen in the real life. Although NASA has already spotted most of the so-called 'planet killers' which are very large and deadly, there is still a small chance it may hit Earth not to mention the expected near-miss that will happen in 2029.
With our advanced technology, those large objects in Earth's neighborhood have already been closely watched and we will have plenty of time to be warned. Astronomers have been watching them closely that they might get near-Earth and enter their "keyholes." Sometimes an Earth-threatening asteroid gets closer or further from Earth based on the different points it orbits around the sun. But along their path are also Earth's keyholes.
"A keyhole is like a door-once it's open, the asteroid will impact the Earth soon after, with high probability," Sung Wook Paek said in a statement.
Just like always, prevention is better than cure. Paek said that the easiest time to stop an asteroid from hitting Earth is before one of the hits a keyhole which will keep it from getting on the route toward an impact saving the Earth or else far more resources and energy, as well as risk, will be involved if it hits a keyhole and then the Earth.
The researchers classified ways in deflecting an asteroid hitting Earth including those exotic ones. They considered using nuclear detonation and impactors as serious methods. However, using nuclear detonation poses risks because it is uncertain as to how the asteroid will behave after the explosion, and using it also opens up political concerns that may cause problems.
Nonetheless, they have formulated three options that could reasonably be prepared when such an event happens:
a. Type "0" is launching a projectile to the asteroid to change its course;
b. Type "1" mission is to get an accurate measurement to know the possible development of the said projectile by sending a scout first;
c. Type "2" mission is to knock the asteroid a bit off course by sending one small impactor and then all information gathered from the first launch will be used to send a second small impact to finish the job.
Three options can only be used depending on the asteroid's mass and relative momentum as well as the time we have before it enters the keyhole. With Type "0", we need to gather precise information on the asteroid's mass, velocity, or make-up otherwise it will just fail given the equipment we have today that can only gather rough information about the planet killers.
Type "1" on the other hand, are more likely to succeed because it can determine the incoming rock's mass, velocity far more precisely. But it takes more time and resources to achieve. Type "2" mission is more applicable but can also take much time and resources to happen.
If we apply it to other well-known planet-killer asteroids Apophis and Bennu, type "1" mission would be best for Apophis given more time and the type "2" mission for Bennu. In both cases, no mission would be successful if the time got too short, explains the researchers.
These principles may pave the way to study other potential "planet-killers" and could help future researchers to think of other ways in deflecting it to avoid what happened millions of years ago. Ultimately, the researchers recommend training machine algorithms to use exact available data in the decision-making when it comes to these scenarios.
