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An asteroid strike would create a huge explosion. NASA feared this might even be mistaken for a nuclear bomb. We wanted folks to know this was a natural event by Mother Nature rather than some sort of man-made event like a missile or something dreadf
探索与发现2014年
Comparing the effects of an airburst with a ground strike, it seems the Chelyabinsk got away lightly. Its estimated that the largest piece to hit the ground weighed 500 kilos, a fraction of the asteroids original mass of 7,000 tonnes. Now if a piece
探索与发现2014年
So was this a near miss for us? If the asteroid had been in a different part of its orbit, so it didnt hit this year but it hit next year, it would have still hit us on February 15th. But instead of coming in over Russia, it would have come in over t
探索与发现2014年
On June 30th, 1908, a huge explosion tore through the forest of Tunguska, Siberia. It was 20 years before the Russians mounted an expedition to the site. What they found astonished them. 60 million trees across an area the size of London had been lev
探索与发现2014年
As the divers have explored further, they discovered the Siluteis are actually part of a huge complex of tounels and caves.In fact, when you look from above, you can see Senluties scattered across hundreds of kilometers.And when they were mapped, it
探索与发现2014年
The meteorite was 15 kilometres across, enough to cause utter devastation across the whole planet. It exploded with a force of 100 million million tones of TNT. The blast sent a giant plume of vaporized rock out into space. A crater was punched 30 ki
探索与发现2014年
Luckily, the very biggest asteroids are few and far between. But there are still plenty of rocks out there that represent a significant danger to us. So, at the summit of an extinct Hawaiian volcano, Professor Nick Kaiser and his colleagues are searc
探索与发现2014年
Tim has developed a map to visualize their location. And on that map, the most important are the Near-Earth asteroids, the ones closest to the planet. On the screen here is a map of the solar system. And Ive got the Sun in the centre and the third pl
探索与发现2014年
On 6th October 2008, asteroid hunter Richard Kowalski saw something that would change the assessment of threats presented by asteroid impacts. The night was proceeding normally and up on the screen came another asteroid. As I continued to make observ
探索与发现2014年
Weknew from the radar measurements where Golevka was within a few tens of metres.And yet it was actually 12 or 15 kilometres away from where it was predicted tobe without Yarkovsky effect. So these very precise radar observations allowedus to see the
探索与发现2014年
Heset out to investigate a hundred-year-old theory that said asteroids werepowered by the Sun itself. It was called the Yarkovsky effect. The Yarkovskyeffect is a very small acceleration and acts on asteroids and what it is is ifyou take a model, the
探索与发现2014年
Well,the early reports are that it is an ordinary chondrite and that means it willbe similar to this one. So this is really exciting for us as scientists becausewe want to know how the planets formed, what was around before the planets, whatthe envir
探索与发现2014年
Itsremarkable how we are able to build up this picture of whats going on millionsof miles away in the solar system. Its one of the joys of science really, justalmost like a detective picking up on those tiny clues to tell a bigger story. Sothat the b
探索与发现2014年
For the residents of the Russian city of Chelyabinsk, the morning of Friday, February 15, 2013 began like any other. As they set off to work in what has become a craze throughout Russia, many recorded their journeys, but these cameras usually used fo
探索与发现2014年
This isnt the first time its happened. Over thelast few years, scientists have examined many other devastating impacts in theEarths past. Using this knowledge, I want to answer the key questions that theChelyabinsk meteor strike raises. Where did thi
探索与发现2014年
I was shocked. I was truly shocked. I never thought Iwould see an event like this over a major city during my lifetime. We couldnt predict this was going to happen. The pieceof rock that actually entered the atmosphere was relatively small, maybe onl
探索与发现2014年
Amazing images. But what can you get out of these asan expert? What it shows us, first of all, is a great record ofthe entry of the object into the Earths atmosphere. So you see it right fromthe moment it really penetrated. And there it is. That is t
探索与发现2014年
The explosion generated a shockwave so massive it wasdetected over 15,000 kilometres away. The low-frequency waves were picked up bymonitoring stations. So it is kind of like a listening network around theworld. Thats right. Theyre not set up for fir
探索与发现2014年
Meteor strikes as big as this may be rare butscientists have a surprisingly detailed knowledge of what meteorites are andwhere they come from. Long before the meteorite reached its explosivefinale in full view of Chelyabinsks dash cams, it had a very
探索与发现2014年
By collecting and comparing meteorites, scientistshave been able to piece together a picture of how they form and these studieshave revealed some of the most remarkable rocks in the solar system. Few places in the world have got as many meteoritesas
探索与发现2014年