This is how NASA intends to stop an asteroid before it slams into our planet, potentially ending civilization as we know it.

SeekerPublished: July 10, 2018
Published: July 10, 2018

In 2135, there is a chance that an asteroid the size of the Empire State building, nicknamed Bennu, will crash into Earth. Okay, so it’s a small chance, but even so, near-Earth Objects - like asteroids and comets - are a real threat. This massive crater in Arizona and this flattened forest in Russia, are believed to be the works of space rocks slamming into our planet. In fact, we avoid close calls from near-Earth Objects all the time, and NASA’s Planetary Defense Coordination Office is responsible for finding, tracking and, in extreme cases, destroying them.

Like the planets, asteroids revolve around the sun in elliptical orbits. Most of them are found in the Asteroid Belt between Mars and Jupiter, but because of their unstable orbits, some have been known to migrate towards Earth. Once an asteroid comes within 28 million miles or 45 million kilometers of Earth’s orbit, the Planetary Defense Office classifies it as an NEA or near-Earth Asteroid. There have been over 18,000 NEAs discovered in the last four decades.

Large asteroids that are over 460 feet or 140 meters in diameter and on track to come within about 5 million miles or 8 million kilometers of Earth’s orbit, are classified as PHAs - potentially hazardous asteroids. And these are the space rocks we should be worried about - like our old friend Bennu here. This PHA is a huge focus of the Planetary Defense Office as it passes through Earth’s orbit every six years. It’s about as wide as five football fields and it weighs more than the Titanic. If it were to slam into Earth, its force would be 80,000 times more powerful than the nuclear bomb that destroyed Hiroshima. But don’t panic… like we said, the chances of this happening are small -  like one in 2,700, and the vast majority of NEAs that enter Earth’s atmosphere disintegrate before reaching the surface.

But for fun, let’s say we do face an Armageddon scenario and Bennu does head straight for Earth, what could NASA do to stop it? Well, this is when the Planetary Defense Office, among others, has to get creative. To deflect an asteroid and prevent impact, scientists have to change the object’s velocity by less than an inch per second years before the projected collision. NASA is investigating two potential ways of doing this. The first method is a gravity tractor. A spacecraft would fly alongside the asteroid for an extended period of time, essentially using its own gravity to slowly pull the NEA away from Earth. But this could take years or even decades to pull off.

The second method is a kinetic impactor, which involves sending one or more high-speed spacecraft into the path of the approaching asteroid. Scientists have already designed prototype, and it’s called HAMMER - Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle. The spacecrafts could serve as either a kinetic impactor or as a transport vehicle for a nuclear device. If the incoming asteroid is detected early, several HAMMER vehicles would be dispatched to collide with the massive rock. Each collision will help further deflect the asteroid off of its path to Earth. If that doesn’t work, scientists would turn to the nuclear option. A HAMMER vehicle would transport a nuclear device near the asteroid and then it would detonate the bomb. The force of the explosion would, ideally, break off a chunk of the space rock, creating jet-like propulsion that would drive the asteroid away from our planet. . But before we make any rash decisions about Bennu’s fate, NASA and the Planetary Defense Office needs to learn more about this PHA and its potential for impact. The spacecraft, OSIRIS-REx is en route to Bennu as we speak to collect samples of the asteroid. But we’ll have to wait till 2023 to get more information on whether or not this massive space rock really could end civilization as we know it.  

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