Earth is about to dodge a bullet. An asteroid will buzz the planet on 15 February, coming closer than many communications satellites.
At 45 metres wide, the space rock is the biggest object in recorded history to swoop this close to Earth. Were it to collide with the planet, it would cause devastation akin to the 1908 Tunguska event that flattened 2000 square kilometres of trees in Siberia.
Astronomers have been tracking the object, called 2012 DA14, since it was discovered a year ago. It will pass about 27,500 kilometres above Earth鈥檚 surface, making its closest approach over Indonesia at 7.24 pm GMT. In dark, clear skies the asteroid will be visible with binoculars.
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Closer look
There is no risk of a collision, but the near miss offers a chance to observe the asteroid up close, for instance, using radar to map its surface. This was done in late 2011 with the asteroid 2005 YU55, which didn鈥檛 come as near to Earth but was a whopping 400 metres across. Astronomers got a detailed view of a surface covered with craters.
鈥�2012 DA14 is a much smaller object, so won鈥檛 look this good,鈥� says Amy Mainzer of NASA鈥檚 Jet Propulsion Lab in Pasadena, California. Still, the radar images should give a better sense of the object鈥檚 shape and spin, which will improve our understanding of its likely future path, she says.
鈥淩ight now astronomers expect that Earth鈥檚 gravity will shift the asteroid鈥檚 orbit closer to the sun, which means it is unlikely to get cosy with our planet again for another 100 years.
Astronomers also hope to read the object鈥檚 spectrum 鈥� chemical clues in its reflected light that can reveal its composition, says JPL鈥檚 Donald Yeomans. This can help studies of all near-Earth asteroids, he says: 鈥淚f you can match up spectral types of asteroids to a corresponding meteorite type, which has been studied to death on the ground, then you know what this thing is made of at the elementary level.鈥�
