NASA is keeping close tabs on a sizable asteroid set to whiz past our planet on Friday in what the US space agency says is the closest flyby ever predicted for such a large object.
About 45 metres in diameter, the asteroid - dubbed 2012 DA 14 - is expected to pass about 27 000 kilometres above the Earth at the time of closest approach, about 2.25pm EST (7.25pm GMT), NASA said.
"This distance is well away from Earth and the swarm of low Earth-orbiting satellites, including the International Space Station," it said in a statement on its website.
Still, "the flyby of 2012 DA14 is the closest-ever predicted approach to Earth for an object this large".
The space agency insisted there was nothing to fear.
"NASA places a high priority on tracking asteroids and protecting our home planet from them," it said.
The asteroid will be visible in eastern Europe, Australia and Asia, according to astronomers, and NASA noted the flyby will provide a "unique opportunity for researchers to study a near-Earth object up close".
NASA's Jet Propulsion Laboratory in California planned a half-hour broadcast incorporating real-time animation to show the asteroid's location.
Meanwhile, the Goldstone Solar System Radar, located in California's Mojave Desert, was poised to take radar images of the asteroid over the coming days to determine its exact size and shape.
The 2012 DA 14 was discovered by chance by astronomers after passing nearby last February.
NASA estimates a smallish asteroid like 2012 DA 14 flies close to the Earth every 40 years, on average, but only hits our planet once every 1200 years.
Astronomers have detected some 9500 celestial bodies of various sizes that pass near Earth, but they estimate that's only a tenth of what's out there.