1	The Meteor That Killed the Dinosaurs
2	65 million years ago...
3	The Earth was ruled by giants
4	For 180 million years...
5	...the dinosaurs ruled the planet.
6	“Dinosaur” means “Terrible Lizard”
7	T-Tex had no natural enemies.
8	But suddenly, 65 million years ago, the dinosaurs and many other animals all died.
9	Why did so many species die out...
10	... so suddenly, leaving only fossils behind?
11	Almost 50% of all life on Earth just died in a short space of time...
12	... including the dinosaurs, the largest animals the Earth has ever seen.
13	Some scientists think that giant volcanos were to blame.
14	Perhaps the gases from a giant volcano poisoned the atmosphere?
15	Others think that the climate changed and the dinosaurs died of cold or hunger.
16	Most scientists though think that a visitor from space was to blame.
17	There are many large rocks flying around in space.
18	These are called “asteroids”
19	The biggest is 940km across, but most are much smaller.
20	Most asteroids orbit the Sun far away from the Earth between Mars and Jupiter, but a few can come close to the Earth.
21	Most scientists think that 65 million years ago a big asteroid hit the Earth...
22	The Moon is covered with many craters where asteroids have hit it.
23
24	Others only a few centimetres across.
25	Each was caused by an asteroid crashing into it.
26	There are craters on the Earth too. The most famous one is in Arizona. It is 1km across.
27	It is only a “small” crater compared to many on the Moon and was made by an asteroid perhaps 100-m across.
28	From space you can hardly see it!
29	...but the explosion was as bad as the biggest bomb ever exploded.
30	The impact happened about 50 000 years ago.
31	This crater in Canada is 100km across and was made when an asteroid 10km across hit the Earth 214 million years ago.
32	Craters have been found all around the world, including in Spain.
33	Some asteroids still hit the Earth
34	The morning of June 30th 1908 a bright light was seen in the sky in Siberia.
35	The light crossing the sky suddenly exploded. People 50km away were blown off their feet.
36	The explosion destroyed the forest
37	Trees were knocked over up to 15km away.
38	Scientists estimate that the explosion may have been 1000 times bigger than the bomb that destroyed Hiroshima.
39	The explosion was probably caused by a small asteroid, no more than 50-m across, hitting the Earth.
40	Were the dinosaurs killed by the impact of an asteroid?
41	For many years scientists looked for a crater that was 65 million years old
42	But they were all either too old...
43	Or too young!
44	But, all around the world scientists have found evidence in the rocks that something strange had happened 65 million years ago.
45	There is a layer of thin, grey rock, exactly 65 million years old.
46	Younger rocks. No dinosaur fossils.
47	The grey rocks contain an metal called Iridium which is very rare on Earth, but more common in asteroids.
48	It seems that a big asteroid hit the Earth 65 million years ago but, where is the crater?
49	The answer is that it fell in the sea.
50	The crater is hidden under the ocean.
51	The asteroid fell in Yucatan in Mexico.
52	An asteroid perhaps 20km across made a crater at least 180km in diameter .
53	Special instruments can see the crater in the ocean floor.
54	Measurements suggest that the crater may be 250km across in all.
55	Dust and small pieces of rock thrown up by the explosion have been found all around the world.
56	The impact would have caused a giant tsunami.
57	Last Christmas we saw what a much smaller tsunami can do...
58	Land and sea changed places...
59	... and many people died.
60	After the fire of the impact...
61	...the tsunami changed the map of the world.
62	Clouds and dust thrown up by the impact would have hidden the Sun for weeks or months.
63	With no sunlight the weather became very cold...
64
65	Could the same thing happen to us one day?
66	Probably not, but...
67	If it did, hundreds of millions of people might die...
68	Perhaps it might happen like this...