A house-size asteroid will give Earth a near-miss on Thursday, passing harmlessly inside the Moon’s orbit while giving experts a rare chance to rehearse for a real-life strike threat.
Dubbed 2012 TC4, the space rock will shave past at an altitude of less than 44,000km just above the 36,000-km plane at which hundreds of geosynchronous satellites orbit the Earth.
That represents about an eighth of the distance between the Earth and the Moon.
Nasa’s Mike Kelley, who leads the exercise to spot, track and intimately probe the transient visitor, insisted there was “no danger. Not even for satellites”.
“We’ve now been observing TC4 for two months, so we have very accurate position information on it, which in turn allows very precise calculations of its orbit,” which will not cross that of Earth nor its satellites, he said.
As its name suggests, the object was first spotted five years ago when it called on Earth at about double Thursday’s projected distance, before disappearing from view.
It is 15 to 30 metres wide — about the size of the meteoroid that exploded in the atmosphere over Chelyabinsk in central Russia in 2013 with 30 times the kinetic energy of the atomic bomb dropped on Hiroshima.
The resulting shockwave blew out the windows of nearly 5,000 buildings and injured more than 1,200 people.
While the Chelyabinsk event caught everyone unawares, TC4 is one of thousands of space rocks whose whereabouts are known.