The latest calculations from NASA experts show that with a probability of 1 in 2700, a very large asteroid Bennu can crash into the Earth. This should happen in the next century. Experts believe that the consequences of a meeting with Bennu can be extremely destructive - up to the complete destruction of life on Earth. Assessing the possible risks, scientists came to the conclusion that there is no guarantee of protecting the planet from collision. According to experts, the methods currently being developed to avoid an encounter with an asteroid are not 100% effective. Nevertheless, these developments are underway.
Considering that the power of the explosion at the moment of collision of an asteroid with the Earth can be about 1200 megatons, which is approximately equivalent to 80 thousand bombs dropped on Hiroshima, it is quite understandable NASA's desire to "overdo it, rather than miss it."
According to the calculations of experts, Bennu's fall to Earth can occur on Sunday, September 25, 2135. Most recently, the journal Acta Astronautica published an article in which scientists shared ideas on how to avoid this catastrophic event.
"At the moment, the likelihood of an asteroid falling to Earth is rather low, but the consequences, in the event of this fall, will certainly be catastrophic for our planet," explains Kirsten Hawley of Livermore National Laboratory and a member of NASA's newly formed planetary security team.
"When it becomes one hundred percent clear to us that the threat of an asteroid fall is indeed inevitable, then we would very much like the Earth to be ready by this time to repel this threat."
The most promising concept of the asteroid threat mitigation system is the HAMMER (Hypervelocity Asteroid Mitigation Mission for Emergency Response) spacecraft project. The device is proposed to be used either as a carrier of a thermonuclear charge, or as an impact projectile - in fact, a battering ram, with which scientists could push Bennu away from a dangerous trajectory.
At the moment, HAMMER is still only a concept. Presumably it will be a spacecraft weighing about 8 tons and about 9 meters high. For comparison: the width of the asteroid Bennu is more than 510 meters. The space stone weighs about 79 million tons, which is about 1,664 times the weight of the Titanic. The launch of the HAMMER apparatus is proposed to be carried out using Delta IV Heavy, which is the second largest launch vehicle in the world after Falcon Heavy from SpaceX.
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"Two realistic options for solving the situation that are currently under consideration are the use of a spacecraft as an impactor or a carrier to deliver a nuclear explosive to deflect an approaching near-Earth object," the study authors report in an article published in the journal Acta Astronautica.
The researchers note that it is extremely important to find the most optimal moment to launch the spacecraft. If the launch is made too early, it will be difficult to predict how the asteroid will behave after impact. If you launch it too late, it will be difficult to displace the giant stone from the trajectory.
Hawley and her colleagues performed calculations and found that the mission could take from 7 to 11 launches of HAMMER to be successful, if 25 years remain before the probable collision. If it remains about 10 years before the collision, then the number of launches required may increase to 53.
Scientists note that with each additional launch, not only will the chances of failure of each particular launch increase, but also the possibility of a complete failure of the mission.
“When multiple launches are required to successfully repel a strike, mission success becomes less optimistic because of the increased chance of failure of each individual launch,” says Livermore National Laboratory physicist Megan Brook Seal.
Researchers believe that it is more preferable to use HAMMER in the form of an impact element, which, appearing in the path of the asteroid, can push it in the other direction and prevent it from reaching Earth. However, due to a number of uncertainties and the short response time available, this method may not be effective.
In this case, a more suitable option, according to experts, would be to equip the HAMMER spacecraft with a nuclear charge and then launch it towards Bennu. The explosion, according to the researchers, will not destroy the asteroid, but can push it out of the dangerous trajectory of approach to Earth. At the same time, it is proposed to detonate a nuclear charge not on the asteroid itself (many are probably now thinking about the movie epic "Armageddon"), but in its immediate vicinity. In this case, one of the sides of the asteroid will be exposed to the most powerful radiation. Its matter will begin to evaporate, and the gases escaping from its surface as a result will create the necessary thrust to change Bennu's direction.
Scientists say there are too many uncertainties and probabilities to speak of a more accurate outcome. In the end, we have more than 100 years before the possible fall of the asteroid to Earth. Nevertheless, thanks to its orbit, Bennu flies close enough by the Earth every six years, so we have the opportunity to track changes in its trajectory. In addition, the OSIRIS-Rex space probe is flying to the asteroid. The purpose of the mission is to approach a space object and take samples of its soil for further study.
To date, astronomers have discovered more than 10,000 potentially dangerous near-Earth objects. Not all of them can be tracked like Bennu, but almost 2,500 of them are similar in size to him. Experts predict that if at least one of them hits the Earth, then the consequences of this blow for humanity will be globally catastrophic.
Researchers estimate that a 1-kilometer space rock is enough to trigger the mass extinction process on the planet. Recall that the dinosaurs had to face the consequences of the fall of an asteroid about 10 kilometers in size.
The impact of an asteroid of any size will be catastrophic, if not for the entire planet, then at least for part of it. The key factor that will help us avoid this fate is our vigilance.
Experts say that in a scenario with an imminent threat of an asteroid fall on the planet, we will be able to reduce the consequences at least a month before this event. True, in this case, we really have to act in the style of the movie "Armageddon", launching a very powerful nuclear charge into the object, which will split the asteroid into many fragments. In this case, damage will be caused only by those fragments of it that will overcome the earth's atmosphere and still fall on the planet.
“Postponing the issue can be the greatest enemy for any mission to repel the asteroid threat. That is why there is a need today to start developing platforms that will help us cope with this threat in the future,”says Hawley.
Nikolay Khizhnyak