An asteroid apocalypse could occur in the year 2135. Here’s how scientists hope to prevent it

If you have any plans on Sept. 21, 2135, be warned that you might end up having to blow them off — no pun intended.

That’s the day that an asteroid measuring 200 metres across could slam into the Earth, unleashing an amount of energy 80,000 times more powerful than the nuclear bomb that devastated Hiroshima in August 1945, according to NASA.

The good news is that the likelihood of asteroid Bennu slamming into Earth is only about 0.04 per cent, and even if it does happen, it won’t completely decimate our planet, Space.com reported back in 2016.

In other words, there will be loss of life — as one might expect in a case of interplanetary collision — but humans won’t go the way of the dinosaurs.

READ MORE: Asteroid that killed dinosaurs almost wiped out mammals

Still, scientists aren’t leaving anything to chance. A group of “planetary defence” experts have been busy drawing up plans and designs for a spacecraft that could be used to deflect the asteroid off-course, according to a paper published in the journal Acta Astronautica last month.

The nine-metre-tall, 8.8-ton spacecraft could be used either to ram into Bennu to nudge it off-course, or to deliver a nuclear warhead to blast the asteroid into oblivion.

Scientists say the first approach is preferable.

“The preferred approach to mitigating an asteroid threat would be to deflect it by ramming a kinetic impactor into it, delivering a gentle nudge large enough and soon enough to slow it down and change its collision course with Earth, but not so large that the object breaks apart,”according to the Lawrence Livermore National Laboratory (LLNL).

It won’t be a last-minute thing. Scientists say the earlier the mission is carried out, the better, because that way, we’d be able to make do with a less drastic deflection.

In the paper, scientists considered scenarios ranging from 10 years in advance to 25 years in advance. If they decide to go with 10 years, they’d need to launch between 34 and 53 rockets to nudge the asteroid away from Earth. If they go with 25 years in advance, they’d need only seven to 11 launches.

What’s more, Bennu regularly passes close enough to the Earth for scientists to be able to measure its orbit and give a few decades’ warning.

READ MORE: Canadian rocks found to contain oldest known evidence of life on Earth

But NASA scientists aren’t content to sit in front of the drawing board for the next century or so.

In September 2016, scientists launched a spacecraft called OSIRIS-REx in Bennu’s direction. The spacecraft’s mission is to map the asteroid, examine its chemical and physical composition and even steal a sample of its surface and bring it back to Earth.

In addition to informing planetary defence plans, the OSIRIS-REx mission also hopes to look into whether Bennu and other asteroids contain precious natural resources that could be of use to humanity.

WATCH: NASA spacecraft heads toward asteroid Bennu

1:27 NASA launches rocket to explore asteroid orbiting sun

If the nuclear bomb approach were taken, scientists say it probably won’t go down like the movie Armaggedon. 

Spoiler alert: The 1998 blockbuster ends with Bruce Willis heroically detonating a nuclear bomb buried beneath the asteroid’s surface, his interstellar suicide bombing giving Earthlings the gift of another day.

Only that would never actually work, according to a group of killjoy scientists writing in the journal Astronomy & Geophysics back in 2012.

LLNL scientists say the nuclear deflection approach would actually involve detonating the bomb some distance from the asteroid, as that would make it possible to control how much energy is transmitted to the asteroid.

“This would flood one side of the asteroid with X-rays, vaporizing a layer of the surface, which would create rocket-like propulsion as vaporized material is ejected from the object,” they wrote.

Scientists have also suggested other, more creative ideas. Instead of flooding one side of the asteroid with X-rays, why not paint it another colour?

That’s an idea suggested by OSIRIS-REx mission scientist Michael Moreau. The paint job wouldn’t just make for more striking Instagram posts for #Bennu, but could alter the asteroid’s thermal properties and change its orbit, Moreau told Gizmodo.

For what it’s worth, scientists are striking a bullish note about their ability to handle the unlikely but frightening threat posed by Bennu, despite some news reports suggesting that the Earth is basically doomed.

“Don’t believe the hype on some sensational headlines out there,” LLNL tweeted. “We are working with NASA to protect the planet from asteroids.”

And that’s vital because although Bennu is unlikely to hit the Earth, scientists say it’s only a matter of time before some other asteroid does.

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