An asteroid the size of a house will zoom past the Earth on Thursday at a distance of some 26,000 miles, NASA said.
That's actually fairly close, when you consider that the moon is about 239,000 miles away.
“It's damn close," Rolf Densing, head of the European Space Operations Centre in Darmstadt, Germany, told The Telegraph. "The farthest satellites are 22,000 miles out, so this is indeed a close miss," he said.
There is no chance the asteroid will hit the Earth. The rock's closest approach will be over Antarctica at 1:42 a.m. ET on Thursday.
The asteroid has not been seen since its 2012 discovery, when it sped past Earth at about one-fourth the distance from Earth to the moon. It's been too distant and too faint to be detected over the last five years.
The space rock, dubbed 2012 TC4, is roughly 45 to 100 feet in size and is hurtling through space at about 16,000 mph.
Are we ready for an asteroid impact?
Thursday, NASA will conduct a drill to see how well its planetary defense system would work if an actual asteroid were heading straight for Earth.
While these sort of drills have been done in the past with pretend asteroids, this one will feature a real asteroid, one that astronomers are confident will miss the Earth.
"The question is: How prepared are we for the next cosmic threat?" said Vishnu Reddy of the University of Arizona and NASA consultant. "So we wanted to test how ready we are for a potential impact by a hazardous asteroid," he said.
"Scientists have always appreciated knowing when an asteroid will make a close approach to and safely pass the Earth because they can make preparations to collect data to characterize and learn as much as possible about it," said Michael Kelley, a NASA program scientist.
NASA's Planetary Defense Coordination Office, which is leading the drill, is the federal entity in charge of coordinating efforts to protect Earth from hazardous asteroids. It's responsible for finding, tracking and characterizing potentially hazardous objects coming near Earth and issuing warnings about possible impacts, should there be an actual threat.
To deflect an asteroid on a collision course with Earth would have to be done years in advance of the predicted impact. The two most promising techniques that NASA is investigating are the "kinetic impactor" (hitting an asteroid with an object to slightly slow it down) and the "gravity tractor" (gravitationally tugging on an asteroid by putting a large mass near it).
Fortunately, no known asteroid poses a significant risk of impact with Earth over the next 100 years, according to NASA.