The massive asteroid Apophis is still considered a potential threat to Earth, but scientists have found that the odds of a collision are lower than previously thought. At the moment, they stand at one in 100,000, new NASA calculations have suggested.

Apophis was first discovered in 2004, with scientists estimating that it was nearly 400 meters wide. It is expected to fly by Earth next on 13 April 2029.

When scientists first studied the asteroid and added to the list of hazardous near-Earth objects, they had found that the space rock had a high chance of hitting Earth in 2029 - earning Apophis's reputation as a 'Doomsday asteroid'.

Now, new calculations made by NASA's Jet Propulsion Laboratory (JPL) have revealed that Apophis' odds of Earth impacting are extremely low - it is very unlikely that a collision will take place at any point in 2029 or on the asteroid's subsequent approach, in 2036.

In fact, it is unlikely to hit us at any point in the next century.

"We cannot yet exclude the possibility that it could impact our planet, but we can calculate that the chance of Earth impact is only one in 100,000 over the next century, which, of course, is extremely small," Paul Chodas, manager of JPL's Center for Near Earth Object Studies, told Astrowatch.net.

Such an collision could still happen in a more distant future, as the orbit of near-Earth objects are chaotic and can change over time. To diminish the risk, ongoing monitoring of Apophis over the next decades will be needed.

Asteroid Apophis
Is asteroid Apophis posing a significant threat?NASA

In coming decades, we may also develop technologies to throw threatening asteroids off course.

Different methods to do this have so far been modelled by scientists including one known as the 'kinetic impactor', which would involve sending a large high-speed spacecraft in the path of an approaching asteroid in an attempt to change its path. Another possible method is known as 'gravity tractor' would involve diverting the asteroid using the gravity of a large spacecraft.

Both methods could work, but they have yet to be tested.

Smaller asteroids are more threatening

In the meantime, the real threat to our planet might not come from huge asteroids like Apophis but from smaller space rocks.

Indeed, while scientists know a lot about the Earth-threatening large asteroid population (those larger than 1 km across), their knowledge is much more limited when it comes to smaller asteroids - in particular those asteroids that are smaller than 100m across. Though less impressive, they could still cause significant damage.

"We can only make impact predictions for asteroids that we have observed, but the most likely scenario is that the Earth is hit by an asteroid that we haven't observed, because it is small, and because small asteroids are much more numerous than large asteroids," Hugh Lewis, Senior Lecturer in Aerospace Engineering at the University of Southampton, previously told IBTimes UK.