Asteroid impacts with Earth are far more common than people realize. In fact, some sources report more than 80,000 meteorites larger than 10 grams come falling to Earth each year. Most of a meteorite is vaporized before striking Earth’s surface. Still, there is a lot of large asteroids in outer space. Some of them passing by Earth very close. Most recently an asteroid of 35 meters called 2017 AG13 flew by earth about 50% closer than the moon, reports Slooh.  So, what are the options in case there is an asteroid on a collision course with Earth?

The collision between Earth and an asteroid a few kilometers in diameter would release as much energy as the simultaneous detonation of several million nuclear weapons.

NEO Program And Preparedness Strategy

It is a fact that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. That is why the awareness of an asteroid impact significantly increased during the time. Since we invented advanced telescopes, they are pointed out to the sky to identify potential space rock threat. Every object which has the closest approach to the Sun less than 1.3 astronomical unit is considered as a near-Earth object – NEO. NASA created NEO program to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. It is already detected 15,448 known NEOs, divided into several orbital subgroups.

With over 90% of the NEO larger than one kilometer already discovered, the Program is now focusing on finding 90% of the NEO population larger than 140 meters

On December 30, 2016, the White House released its NEO Preparedness Strategy with details how to stop such event and how to act if it hits.

When we speak about defensive methods, the most important fact, besides the asteroid’s size, is time. According to  Joseph Nuth, a researcher with NASA’s Goddard Space Flight Center, it would take five years to design, build, and launch a spacecraft to either deflect or destroy any space rock. These spacecraft would have a nuclear device, which should be used only when we are absolutely sure that the asteroid is on our way.

Another strategy is known under the name kinetic impactor. It includes sending high-speed spacecraft into the path of an asteroid to deflect it into a different trajectory. The problem with this strategy is that it would be required 20 years to build such impactor and to launch it to nudge the asteroid. Also, it probably doesn’t work on a very large asteroid.

Some other methods include using lasers, catching the NEO and dragging it away,  building spacecraft which would be used as asteroid gravity tractor, focusing the solar energy to the rock’s surface to melting it or just throwing the rockets into it.

Whatever strategy we use, it needs a time. Perhaps the time is currently our biggest enemy. All strategies that we have, works only if we have enough time to prepare. For any sudden, unforeseen events, we have no defense.