But only when the need is greatest.

There are countless flying space rocks in our cosmic backyard. Some are in wide orbits, while others may be on a collision course with Earth. Scientists are doing everything they can to map dangerous near-Earth objects so that we are not unexpectedly surprised at the last minute. But what if the latter does happen?

deflect

When an asteroid heads straight for Earth, scientists prefer a mission to alter its orbit. During such a mission, the asteroid is gently tapped, forcing a small change in the asteroid’s orbital speed. In this case, most of the asteroid will be held together, while the object’s orbit has been carefully deflected and it will no longer touch Earth.

DART mission
Whether this approach is effective will be tested during the upcoming DART mission. Soon this spacecraft will be heading for the asteroid Didymos to attempt to alter its orbit. DART will ram the asteroid’s moon to form an impact crater. With this, the researchers hope to move the asteroid into another orbit. The spacecraft HERA will then be launched in a few years to further investigate the aftermath of the bombing. It’s an experiment in what NASA calls “planetary defense.” Should an asteroid ever hit Earth, we may be able to prevent an impact thanks to the knowledge and skills we gain during the DART mission.

It seems like a promising approach. But what if we suddenly hear too short in advance that an asteroid is on a collision course with Earth? Although scientists are doing everything they can to properly map the orbits of asteroids, we must be prepared for any possible scenario, as many asteroids in the vicinity of Earth remain undiscovered.

nuclear bomb

One possibility to deal with an imminent impact of an asteroid in the short term is to completely destroy it. This can be done, for example, by blowing it up with a nuclear bomb and shattering it into countless pieces. This way naturally appeals to the imagination and sounds like the scenario of a disaster movie – the famous Armageddon to be precise. Although in theory it is an option, the question is of course to what extent this is actually feasible. And so researchers took it to the test.

Simulation

In a simulation, the researchers simulated a Bennu-shaped asteroid with a diameter of 100 meters. They then studied the extent to which a bomb with an energy output of 1 megaton deployed just a few meters above the surface could destroy the object and prevent the fragments of the asteroid-dismembered asteroid from landing on Earth (see video below). . “One of the challenges is that you have to model all orbits,” said study leader Patrick King. “That is generally much more complicated than modeling a simple deflection. Nevertheless, we must try to address these challenges if we are to assess this method as a possible strategy.”

The results are reassuring. Because if such a destruction mission were carried out just two months before the impact date, the nuclear bomb would be able to reduce the amount of impact mass by a factor of 1000 or more (99.9 percent of the mass will miss the Earth). For a larger asteroid, the outcome is slightly less favorable. Though 99 percent of the mass will still miss Earth if the mission takes place six months before the doomed day.

Debris

It is crucial that the entire asteroid is crushed to rubble. “If we were to see a dangerous object, we would have to break it so thoroughly that the resulting fragments would miss most of the Earth,” said study researcher Michael Owen. “However, this is a complicated job issue. If you break an asteroid into pieces, the resulting cloud of fragments will each follow their own path around the sun. That cloud may extend into a curving stream of fragments around the defunct asteroid’s original path. How fast those pieces are spreading (combined with how long it takes for the cloud to cross Earth’s path) tells us how much will hit Earth.”

In any case, the findings of the study show that deploying a nuclear bomb is a very effective way to protect the earth. But the approach should be seen as an emergency measure and is especially suitable when we discover a potentially dangerous asteroid very late. “We focused on ‘late’ detections, meaning the impacting body is broken down shortly before impact,” King says. “If you have enough time – usually ten-year timescales – the deflection of the colliding celestial body is generally preferable.”