Having faced a deadly coronavirus pandemic for two years, the last thing humanity needs is an Armageddon scenario where a huge asteroid is hurtling towards the earth.
The “potentially hazardous” asteroid named 4660 Nereus is set to make a ‘close’ pass of the earth next week - a mere fortnight before we celebrate Christmas.
It comes after an asteroid that was roughly the size of the London Eye called 1994 WR12 passed close to our home planet in November.
Work on how to stop big space rocks from hitting us is still very much in its infancy, with the US space agency having only just launched humanity’s first-ever attempt to change an asteroid’s course.
So should humanity worry about 4660 Nereus, how does Nasa know it could be deadly - and what is the space agency doing to prevent an Armageddon scenario?
Here’s what you need to know.
Will 4660 Nereus hit earth?
On 11 December 2021, the 330m-long asteroid 4660 Nereus is set to whistle past us at a mindblowing speed of 6.58 kilometres-a-second, some 2.4 million miles away from earth.
While that might not seem particularly close - after all, you’d have to drive around the earth 100 times to travel that distance - Nasa has classified the asteroid as a “potentially hazardous” near-earth object.
This is because it is bigger than 150m and will approach our planet at less than half the distance from the earth to the sun (roughly 93 million miles), meaning any slight deviation in its orbit could put it on a collision course with our planet.
It is also coming much closer to earth than 1994 WR12, which was 3.8 million miles away at its closest approach on Monday 29 November.
Although 4660 Nereus is likely to pose no threat in 2021, it is set to come much closer to the earth in the future.
On Valentine’s Day in 2060, it will come within 745,000 miles of earth.
So it might be worth buying those flowers or getting that proposal done well in advance.
How does Nasa track ‘dangerous’ asteroids?
Nasa tracks dangerous asteroids through its Centre for Near-Earth Object Studies.
Since 1968, it has tracked more than 1,000 asteroids that have passed close to our home planet using radar - a technique which allows the space agency to accurately map the orbit, size and shape of space rocks.
Through telescopes, Nasa has also managed to map 27,323 asteroids that could threaten the earth.
Just under 10,000 of these are 140m or larger and 891 are more than a kilometre in size.
To put the potential power of these rocks into perspective, the asteroid which caused the Chelyabinsk explosion in Russia in 2013 was just 20m in size.
This event saw up to 33 times as much energy released as the atomic bomb the US dropped on the Japanese city of Hiroshima in World War Two.
Its shockwaves blew out windows in more than 3,600 apartment blocks.
And it injured 1,200 people, with some having suffered skin and retinal burns due to the space rock shining up to 30 times brighter than the sun as it entered the earth’s atmosphere.
Nasa says there is no “significant chance” any of these near-earth asteroids will hit earth in the next 100 years.
But it estimates there could be more than 25,000 large near-earth objects in space, meaning it has discovered less than half of the potentially deadly asteroids out there.
By tracking these space rocks and finding out more about their size, shape, mass, structure and what they’re made of, the US space agency hopes to come up with ways of diverting one should it threaten earth.
What is the Nasa Dart asteroid mission?
On 24 November, Nasa launched its Double Asteroid Redirection Test (Dart) mission.
This one-way experimental voyage will see a spacecraft collide with an asteroid in a bid to alter the space rock’s course.
Should it prove successful, it could provide a way of protecting the earth from asteroids.
Dart will be heading to the 780-metre rock Didymos and a 160-metre asteroid which orbits it, called Dimorphos.
These asteroids have been chosen because they are easily traceable through earth-based telescopes.
So, any changes to their courses can be tracked accurately.
Neither of them are thought to be a danger to the earth.
When the spacecraft reaches the pair of space rocks at the end of September 2022, it will hit Dimorphos at four miles per second - a speed scientists believe will be enough to hit the rock off course.
In four years’ time, a European Space Agency (ESA) spacecraft named Hera will arrive at the asteroids to inspect Dart’s crater and survey their respective masses.
What is an asteroid?
Asteroids are rocky fragments left over from the early days of the solar system, which formed about 4.6 billion years ago.
They are believed to be the remnants of collisions between planets and moons.
Many of these rocks orbit the sun between Mars and Jupiter in a part of space known as the Asteroid Belt.
Scientists estimate there are millions of asteroids in this part of space - some of which are hundreds of kilometres in size.
An even larger collection of massive asteroids can be found at the extremities of the solar system, which is known as the Kuiper Belt.
Sometimes, these asteroids change their orbits if they are influenced by the gravitational tug of planets.
They can also collide with one another in events which can throw out smaller, but potentially deadly, shards of space rock.
It is one such stray asteroid, believed to have measured around six miles in size, that wiped out the dinosaurs 66 million years ago and led to mammals’ dominance of the planet.
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