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NASA scientists calculated the exact date an asteroid could hit Earth with the force of at least 24 nuclear bombs. Thankfully, it's a long way off.

Marianne Guenot   

NASA scientists calculated the exact date an asteroid could hit Earth with the force of at least 24 nuclear bombs. Thankfully, it's a long way off.
  • Asteroid Bennu has a slim chance of hitting our planet on September 24, 2182, NASA said.
  • It would release as much energy as about 24 nuclear bombs, so NASA is keeping a close eye on it.

What are you doing on September 24, 2182? You may want to clear your calendar because scientists think an asteroid may hit Earth.

NASA scientists are keeping a close eye on asteroid Bennu, a 1,610-foot-wide cosmic object that could smash into our planet.

If Bennu were to hit the Earth, it would slam into the surface at about seven miles per second. It is so big that it could release 1,400 megatons of energy, per a NASA calculation — which is at least 24 times as powerful as the nuclear weapon, the Tsar Bomba.

Thankfully, the chances of this happening are very slim — about 1 in 2,700, per a 2021 study.

Still, NASA is interested enough in Bennu to launch a seven-year-long mission to study it, which is due to bring back a precious sample from the asteroid in a dramatic landing on Sunday.

This mission could help us better forecast the future of our cosmic neighbor, but it could also provide unprecedented insight into the formation of the Earth.

Bennu is bigger than the Empire State Building

Bennu belongs to a category of asteroids called "city-killers." That means that if it were to hit the Earth — the probability of which is zero until 2,100 and very small after that, per NASA — it would be powerful enough to flatten a large city.

The diamond-shaped asteroid is no stranger to Earth's neighborhood. Its long orbit around the sun means it approaches the Earth about every six years. But it usually keeps a polite distance from us — it's never come closer than about 3 million miles from Earth.

As it makes its way around the solar system, Bennu's orbit can change, and that's where it gets a little riskier.

To make its 2182 appointment with the Earth, Bennu will need to pass within a very small window in space — a "gravitational keyhole" — in 2135. That would shift its orbit perfectly to line up with our planet.

But there's still a 99.96% chance it will miss us on that date.

We need to know more about large Earth-bound asteroids

Even though the risk is low, large asteroids near Earth need to be taken seriously. Of the ones we know, most pose little to no risk to our planet.

But the concern is that these kinds of objects could be hiding from view, meaning NASA can only spot them moments before they hit.

NASA estimates that 60% of the city-killer-sized asteroids that could come in proximity to Earth are unknown at this time, and even bigger rocks could be hidden in the light of the sun, a known blindspot for observation from Earth.

The Chelyabinsk incident provided a stark reminder of this fact in 2013 when a house-sized asteroid unexpectedly appeared over the city before exploding, breaking windows, damaging buildings, and injuring more than 1,400 people.

That's why NASA has been working to improve its forecasting of so-called Near Earth Objects.

Studying an object like Bennu, which is easy to observe and comes close enough to Earth that we can send a mission there, is important for understanding more about these objects.

NASA's mission to Bennu, a probe called Osiris-Rex that was launched in 2016, could provide more clues about how asteroids sail in the cosmos. For instance, one of the mission's objectives is to understand how the light from the sun, as it is absorbed and re-radiated, could affect Bennu's orbit.

Bennu could shed light on our planet's birth

There's more to Bennu than its destructive potential, and that's what NASA is most interested in for Osiris-Rex.

Bennu was likely created at about the same time as our planet, about 4.5 billion years ago, NASA said.

Traces of what happened at that time have long been erased from our planet, under millions of years of erosion. But Bennu could still be carrying elements from then, frozen in time as it sails through the cosmos, per NASA.

That's why NASA is eagerly awaiting the return of its Osiris-Rex spacecraft, which is carrying a few ounces of precious dust collected from Bennu in 2020.

This little probe, which has been sailing back from Bennu since May 10, 2021, should deliver its payload, a capsule containing the precious sample, as it passes about 63,000 miles from the Earth in the early hours of Sunday morning.

The capsule is planned to fall back to Earth later Sunday morning, landing in Utah around 10:55 a.m. ET.

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