The trail of a falling object is seen above the Urals city of Chelyabinsk February 15, 2013, in this picture.
The meteor explosion over Russia that injured more than 500 people and damaged hundreds of buildings was not caused by an asteroid zooming close by the Earth today (Feb.15), a NASA scientist says.
NASA asteroid expert Don Yeomans, head of the agency's Near-Earth Object Program Office, told SPACE.com that the object which exploded over a thinly inhabited stretch of eastern Europe today was most likely an exploding fireball known as a bolide.
More than 500 people were injured, mostly by glass cuts when windows shattered during the blast, according to the Russian Emergency Ministry.
"If the reports of ground damage can be verified, it might suggest an object whose original size was several meters in extent before entering the atmosphere, fragmenting and exploding due to the unequal pressure on the leading side vs the trailing side (it pancaked and exploded)," Yeomans told SPACE.com in an email. "It is far too early to provide estimates of the energy released or provide a reliable estimate of the original size."
Yeoman stressed that the bolide event was likely not associated at all with the incoming asteroid 2012 DA14, which will fly within 17,200 miles (27,000 kilometers) of Earth when it passes safely by our planet today.
"The asteroid will travel south to north," Yeomans said. "The bolide trail was not south to north and the separation in time between the fireball and 2012 DA14 close approach is significant."
Asteroid 2012 DA14 is 150 feet (45 meters) wide — about half the size of a football field — and will make its closest approach to Earth at 2:24 p.m. EST (1924 GMT) when it passes over Indonesia. It will be about 5,000 miles (8,046 kilometers) closer to Earth than the communications satellites circling the planet in geosynchronous orbits.
NASA scientists and professional and amateur astronomers around the world have been tracking asteroid 2012 DA14 since it was first discovered by a team of amateurs in February 2012. Not only does the asteroid pose no threat to Earth during today's flyby, but it will not hit Earth for the foreseeable future, NASA scientists have said.
俄罗斯近日（2月15日）发生的陨石爆炸已造成超过500人受伤，毁坏了数百座建筑。美国宇航局一位科学家表示，这次陨石爆炸并不是由小行星撞击地球引起的。
美国宇航局小行星专家、近地天体项目办公室负责人唐-耶麦斯告诉SPACE.com网站，在人烟稀少的远东地区上空爆炸的这颗天体很有可能是一颗火球，也称为火流星。
俄罗斯紧急情况部称，超过500人在这次爆炸中受伤，绝大多数是由于爆炸中玻璃震碎而被划伤。
耶麦斯在一封电邮中告诉SPACE.com网站：“如果地面损失情况得以证实，那就表明这颗天体进入大气层之前有几米长，由于头部和尾部的压力不平均而发生碎裂并爆炸（它平坠着陆并发生爆炸）。现在来估计能量释放或者原始大小还为时尚早。”
耶麦斯强调说，这起火流星爆炸事件与即将掠过地球的小行星2012 DA14没有任何关系、小行星2012 DA14会安全地近距离掠过地球，与地球的距离不超过1.72英里（2.7千米）。
耶麦斯说：“这颗小行星将由南至北掠过地球，而火流星的飞行轨迹不是从南向北，而且火流星爆炸与小行星2012 DA14掠过地球的时间相差很大。”
小行星2012 DA14有150英尺（45米）宽，相当于半个足球场那么大，将在美国东部时间下午2点24分（北京时间16日凌晨）抵达近地点，在印尼上空飞过。它比环绕地球飞行的同步通讯卫星离地球还要近五千英里（8046千米）。
2012年2月，一组业余爱好者首次发现了2012 DA14，美国宇航局科学家以及来自全球的专家及业余天文爱好者一直在追踪它。美国宇航局科学家表示，这颗小行星不但没有在此次掠过地球时对地球构成威胁，而且今后也不会撞击地球。
bolide: 火流星，爆发流星