An asteroid about the size of one that levelled more than 800 square miles of forest in Siberia a century ago just buzzed Earth, Nasa said.
The asteroid, named 2009 DD45, was about 48,800 miles from Earth when it zipped past early on Monday, Nasa's Jet Propulsion Laboratory reported.
That is just twice as high as the orbits of some telecommunications satellites and about a fifth of the distance to the Moon.
"This was pretty darn close," astronomer Timothy Spahr of the Harvard-Smithsonian Centre for Astrophysics said.
But not as close as the tiny meteoroid 2004 FU162, which came within 4,000 miles in 2004.
The space rock measured between 69 and 154 feet in diameter. The Planetary Society said that made it about the same size as the asteroid that exploded over Siberia in 1908.
Scientists at the Siding Spring Observatory in Australia spotted 2009 DD45 and began tracking it in late February when it was about one million miles away.
Mr Spahr said he knew within an hour of that discovery that it would pose no threat to Earth.
Of the known space rocks, the next time an object will get closer to Earth will be in 2029 when an 885ft asteroid called 99942 Apophis comes within 20,000 miles, says Donald Yeomans of Nasa's Near-Earth Object Programme at the Jet Propulsion Laboratory in Pasadena, California.
Last year, the asteroid 2008 TC3 harmlessly burned up in Earth's atmosphere over Africa 19 hours after it was discovered. Astronomers gave a six-hour notice warning of that fiery plunge