An asteroid spotted by amateur astronomers only after it had skimmed the Earth will come even closer next February, but without posing a threat, the European Space Agency (ESA) said on Friday.
Around 50 metres (150 feet) long, asteroid 2012 DA14 has stoked concern about planetary preparedness against rogue rocks.
It was detected on February 22 only after it had flashed by at a gap of 2.5 million kilometres (1.6 million miles), or about seven times the distance between Earth and the Moon.
Next February 15, it will pass Earth at just 24,000 kilometres (15,000 miles), meaning it will zip between the planet and satellites in geostationary orbit, which is 35,800 kms (21,800 miles) above the equator, ESA said.
"This is a safe distance, but it is still close enough to make the asteroid visible in normal binoculars," said Detlef Koschny at ESA's Space Situational Awareness office.
Preliminary calculations of 2012 DA14 show it orbits the Sun in 366 and a quarter days, which is a day more than Earth's year.
It jumps inside and outside of the path of Earth twice a year, according to the team who discovered it.
Next February's flyby, while not a threat, will help determine whether the asteroid's trajectory is affected -- towards either safety or risk -- by the gravitational tug of the Earth and the Moon.
According to calculations derived from NASA's Near Earth Object (NEO) Program website, 2012 DA14 has a mass of around 120,000 tonnes. It will be at its closest point at about 1926 GMT on February 15.
A US-led mission is making inroads into counting the numbers of very large NEOs that can be a kilometre (half a mile) or more in length.
Monsters such as these are capable of apocalyptic damage, as was famously the case with the asteroid or comet that ended the long reign of the dinosaurs some 65 million years ago.
But a more arduous greater task is to spot the hundreds of thousands of smaller rocks measuring tens of metres (dozens of feet across), that -- if they remained as large chunks after entering the atmosphere -- could wipe out a city or cause a tsunami.
An object roughly the size of 2012 DA14 caused the so-called Tunguska Event in Siberia in 1908.
Heated by friction with the atmosphere, it exploded with the power of a thousand atomic bombs, flattening 80 million trees in a swath of more than 2,000 square kms (800 sq. miles).
Discovering 2012 DA14 was a coup for the La Sagra Sky Observatory, near Granada in southeastern Spain. The telescope is located at an altitude of 1,700m (5,500 feet) in one of the least light-polluted places in Europe.
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