南极洲发现太空陨石爆炸的新线索
文章来源:未知 文章作者:meng 发布时间:2010-03-04 06:39 字体: [ ]  进入论坛
(单词翻译:双击或拖选)

A large space rock may have exploded over Antarctica thousands of years ago, showering a large area with debris1, according to new research.

一项新研究显示,数千年前,一大块太空岩石可能在南极洲上空爆炸,碎片散落在一大片区域。

The team
The team's findings could help in the search for other ancient "airbursts"

The evidence comes from accumulations(累积) of tiny meteoritic2(陨石的) particles and a layer of extraterrestrial(地球外的) dust found in Antarctic ice cores.

Details of the work were presented at a major science conference in Texas.

The event would have been similar to the Tunguska event, which flattened3 a large area of Siberian forest in 1908.

It is thought to have been a so-called "airburst(炸弹在空中爆炸) " in which a space rock does not reach the ground, but rather explodes in the atmosphere.

The research is based on a study of extraterrestrial debris found in granite4(花岗岩) from Miller5 Butte, in the Transantarctic Mountains, and a layer of cosmic dust represented in two Antarctic ice cores.

The debris from the mountains includes micrometeorites(微陨石) and tiny particles called spherules(小球体) . The study's authors think these spherules could be material eroded7 from a stony8 meteorite6 as it was heated up on its way through our atmosphere.

The spherules could potentially provide a signature to look for evidence of "airbursts" in the geological record.

Wide area

The results were the subject of a presentation at the Lunar and Planetary Science Conference (LPSC) in The Woodlands, Texas.

A layer of extraterrestrial dust has been found in both the Dome9 C and Dome Fuji ice cores from Antarctica. The dust in both cores is dated to about 481,000 years ago - and is therefore likely to derive10 from the same event.

The team, comprising Luigi Folco and Matthias van Ginneken from the University of Siena, Italy, and Phil Bland11 from Imperial College London, UK, now conclude that the Dome C and Dome Fuji dust layers are also paired with debris from the Transantarctic Mountains(南极洲横贯山地) .

They point to strong similarities in the texture12 and composition of the debris found in the ice cores and that found in the granite.

However, the sites are more than 2,900km apart. For cosmic debris to be spread over such a wide area, the researchers propose that an airburst is the most likely explanation.

They estimate that it could have been caused by an object weighing 100,000 tonnes.

"We've got similar material spread over a very large area. It's difficult to do that with any other mechanism," said co-author Dr Bland.

The Tunguska impact was caused by a space rock some tens of metres across that detonated(引爆,爆炸) 5-10km above the ground. The blast flattened some 2,000 sq km of Siberian forest, knocking people to the ground about 60km from the epicentre(震中) .

Airbursts on the scale of the Tunguska event are thought to occur every 500-1,000 years on Earth. This figure is based on computer modelling by Dr Bland and his colleagues.

These results are consistent with(与……一致) an analysis of airbursts in the atmosphere gathered by US Department of Defense13 satellites from the 1960s onwards.

"These events are tricky14 to spot after they happen. If you go to Tunguska now, you've really got your work cut out trying to find any trace of that event - and that was 1908," Dr Bland told BBC News.

"What makes [the] work so exciting is that it may give us a way of spotting these events in the geological record. If these spherules are the signature, we know what to look for in future."



点击收听单词发音收听单词发音  

1 debris debris     
n.瓦砾堆,废墟,碎片
参考例句:
  • After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
  • Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上,导致蛀牙。
2 meteoritic 764fbc41c009161f6b18cf20096cc96b     
adj.陨石的
参考例句:
  • The momentum of the particles was deduced from meteoritic velocities. 粒子的冲量可以从陨石速度推导出来。 来自互联网
3 flattened 1d5d9fedd9ab44a19d9f30a0b81f79a8     
[医](水)平扁的,弄平的
参考例句:
  • She flattened her nose and lips against the window. 她把鼻子和嘴唇紧贴着窗户。
  • I flattened myself against the wall to let them pass. 我身体紧靠着墙让他们通过。
4 granite Kyqyu     
adj.花岗岩,花岗石
参考例句:
  • They squared a block of granite.他们把一块花岗岩加工成四方形。
  • The granite overlies the older rocks.花岗岩躺在磨损的岩石上面。
5 miller ZD6xf     
n.磨坊主
参考例句:
  • Every miller draws water to his own mill.磨坊主都往自己磨里注水。
  • The skilful miller killed millions of lions with his ski.技术娴熟的磨坊主用雪橇杀死了上百万头狮子。
6 meteorite 2wNy1     
n.陨石;流星
参考例句:
  • The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
  • The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。
7 eroded f1d64e7cb6e68a5e1444e173c24e672e     
adj. 被侵蚀的,有蚀痕的 动词erode的过去式和过去分词形式
参考例句:
  • The cliff face has been steadily eroded by the sea. 峭壁表面逐渐被海水侵蚀。
  • The stream eroded a channel in the solid rock. 小溪在硬石中侵蚀成一条水道。
8 stony qu1wX     
adj.石头的,多石头的,冷酷的,无情的
参考例句:
  • The ground is too dry and stony.这块地太干,而且布满了石头。
  • He listened to her story with a stony expression.他带着冷漠的表情听她讲经历。
9 dome 7s2xC     
n.圆屋顶,拱顶
参考例句:
  • The dome was supported by white marble columns.圆顶由白色大理石柱支撑着。
  • They formed the dome with the tree's branches.他们用树枝搭成圆屋顶。
10 derive hmLzH     
v.取得;导出;引申;来自;源自;出自
参考例句:
  • We derive our sustenance from the land.我们从土地获取食物。
  • We shall derive much benefit from reading good novels.我们将从优秀小说中获得很大好处。
11 bland dW1zi     
adj.淡而无味的,温和的,无刺激性的
参考例句:
  • He eats bland food because of his stomach trouble.他因胃病而吃清淡的食物。
  • This soup is too bland for me.这汤我喝起来偏淡。
12 texture kpmwQ     
n.(织物)质地;(材料)构造;结构;肌理
参考例句:
  • We could feel the smooth texture of silk.我们能感觉出丝绸的光滑质地。
  • Her skin has a fine texture.她的皮肤细腻。
13 defense AxbxB     
n.防御,保卫;[pl.]防务工事;辩护,答辩
参考例句:
  • The accused has the right to defense.被告人有权获得辩护。
  • The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。
14 tricky 9fCzyd     
adj.狡猾的,奸诈的;(工作等)棘手的,微妙的
参考例句:
  • I'm in a rather tricky position.Can you help me out?我的处境很棘手,你能帮我吗?
  • He avoided this tricky question and talked in generalities.他回避了这个非常微妙的问题,只做了个笼统的表述。
TAG标签: dust rock space Antarctica
发表评论
请自觉遵守互联网相关的政策法规,严禁发布色情、暴力、反动的言论。
评价:
表情:
验证码:点击我更换图片