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.俄羅斯近日（2月15日）發(fā)生的隕石爆炸已造成超過500人受傷，毀壞了數(shù)百座建筑。美國宇航局一位科學(xué)家表示，這次隕石爆炸并不是由小行星撞擊地球引起的。

美國宇航局小行星專家、近地天體項目辦公室負責(zé)人唐-耶麥斯告訴SPACE.com網(wǎng)站，在人煙稀少的遠東地區(qū)上空爆炸的這顆天體很有可能是一顆火球，也稱為火流星。

俄羅斯緊急情況部稱，超過500人在這次爆炸中受傷，絕大多數(shù)是由于爆炸中玻璃震碎而被劃傷。

耶麥斯在一封電郵中告訴SPACE.com網(wǎng)站：“如果地面損失情況得以證實，那就表明這顆天體進入大氣層之前有幾米長，由于頭部和尾部的壓力不平均而發(fā)生碎裂并爆炸（它平墜著陸并發(fā)生爆炸）?，F(xiàn)在來估計能量釋放或者原始大小還為時尚早?！?/p>

耶麥斯強調(diào)說，這起火流星爆炸事件與即將掠過地球的小行星2012 DA14沒有任何關(guān)系、小行星2012 DA14會安全地近距離掠過地球，與地球的距離不超過1.72英里（2.7千米）。

耶麥斯說：“這顆小行星將由南至北掠過地球，而火流星的飛行軌跡不是從南向北，而且火流星爆炸與小行星2012 DA14掠過地球的時間相差很大?！?/p>

小行星2012 DA14有150英尺（45米）寬，相當(dāng)于半個足球場那么大，將在美國東部時間下午2點24分（北京時間16日凌晨）抵達近地點，在印尼上空飛過。它比環(huán)繞地球飛行的同步通訊衛(wèi)星離地球還要近五千英里（8046千米）。

2012年2月，一組業(yè)余愛好者首次發(fā)現(xiàn)了2012 DA14，美國宇航局科學(xué)家以及來自全球的專家及業(yè)余天文愛好者一直在追蹤它。美國宇航局科學(xué)家表示，這顆小行星不但沒有在此次掠過地球時對地球構(gòu)成威脅，而且今后也不會撞擊地球。