An asteroid is passing increasingly close to Earth and is roughly the size of the house.
This space rock will be hurtling past our planet at a distance of roughly 42,000km – bringing it within the Moon's orbit and just above the altitude of communication satellites.
According to the NASA scientists, there is no risk of an impact. However, the flyby does provide them with the opportunity to test their asteroid warning systems. A global network of telescopes will be used to closely monitor the object.
According to Paul Chados, manager of Nasa's Centre for Near Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory in California: "We are going to use this asteroid to practice the system that would observe an asteroid, characterise it and compute how close it is going to come, in case someday we have on that is on the way inbound and might hit."
The asteroid, named 2012 TC4, was first spotted five years ago and is estimated to be between 15m and 30m in size – which is relatively small.
However, even space rocks on that scale are dangerous to our planet if they strike.
For example, when a 20m-wide asteroid exploded over Chelyabinsk in central Russia in 2013, it hit the atmosphere with energy estimated to be equivalent to 500,000 tonnes of TNT. This caused a shockwave that damaged buildings and injured more than a thousand people.
Nasa scientists have spent the last two months tracking this asteroid and say that their calculations show that it will safely clear the Earth and poses no threat.
Instead, they will use this close approach as an opportunity to rehearse for future potential strikes.
While the risk of an asteroid hitting was small, Dr Chodas said it was prudent to plan ahead.
"Nasa search programmes are getting better and better at finding asteroids," he explained.
"It's been a priority to find the large asteroids first. So far the Nasa surveys have found 95% of the asteroids that are on kilometre and larger – these are the ones that could cause a global catastrophe.
"Now we are working our way down to smaller ones – 130 in size and larger – and we are around 30% on that.
"This little one – we are not trying to find all of the ones this size. It is just a convenient asteroid coming by that we can practice our tracking techniques on."
Dr Chados added that, if an asteroid was discovered to be heading straight for Earth, scientists were looking at various techniques to avert a potential disaster.
"If we had enough warning time – five or ten years – then we could do something about it, especially if it's on the small side.
"We could go up and move it, change its velocity years ahead, and that would be enough to move it away from a collision course."
The asteroid's closest approach to Earth on today will be over Antarctica at 05:42 GMT.