This week, 4660 Nereus, a space rock the size of the Eiffel Tower, will fly near to Earth.
How does Nasa know this asteroid may be dangerous to our planet?
What you need to know.
Is 4660 Nereus a hazard
At 6.58 kilometres per second, asteroid 4660 Nereus will fly by Earth on December 11, 2021.
While that may not seem like much, Nasa has classified the asteroid as a “potentially hazardous” near-Earth object.
A little departure in its orbit might put it on a collision course with our planet, as it is larger than 150m and would approach at less than half the distance from Earth to the sun (about 93 million miles).
Although 4660 Nereus appears harmless in 2021, it is expected to approach Earth in the future.
In 2060, it will pass within 745,000 miles of Earth.
Nasa tracks ‘dangerous' asteroids.
NASA's Center for Near-Earth Object Studies monitors potentially destructive asteroids.
Since 1968, it has used radar to track over 1,000 asteroids that have been close to Earth, allowing it to record their orbit, size, and shape.
Using telescopes, Nasa has identified 27,323 potentially hazardous asteroids.
This includes 9,886 asteroids 140m or larger and 891 km or larger.
NASA thinks none of these asteroids will reach Earth in the next 100 years.
Asteroids larger than 140m are estimated to be over 25,000 in space, indicating we have only recorded fewer than half of the potentially deadly asteroids.
To redirect an asteroid that threatens Earth, the US Space Agency said it will watch them and learn more about their size, shape, mass, structure, and composition.
Asteroid is a rocky remnant from the formation of the solar system 4.6 billion years ago.
Scientists estimate there are millions of asteroids between Mars and Jupiter, some measuring hundreds of kilometres in size.
These asteroids' orbits can shift due to planets' gravitational pull.
They can also collide, ejecting tiny but potentially lethal pieces of space debris.
One such errant asteroid, estimated to be six miles in size, wiped out the dinosaurs 66 million years ago, paving the way for mammals to rule the globe.