DARK SKIES: Asteroid, meteor - what's the difference?
ON ANY night of any week, you will see a 'shooting star', which is actually a meteor - tiny grains of space dust burning up from friction through the atmosphere.
When they land on Earth they are called meteorites and in some cases are quite large, up to a few metres in size and weighing up to two tonnes.
Of all the meteors we see, however, 99 per cent burn up and fall to Earth as dust.
Back in 1984, a meteor dubbed 'Alanhills 84' was found to be a piece of Mars rock blasted into space by a meteor striking the Martian surface.
About a dozen times a year our planet passes through the tails of small comets that regularly orbit the Sun.
As we pass through those dusty tails, hundreds of tiny particles enter and burn into the atmosphere and we see them as a 'meteor shower'.
Unfortunately, due to our southern latitudes, those events are not as spectacular as those in the north. Back in pagan times, however, meteors were thought to be omens of doom and gloom, while lightning and thunder were the anger and revenge of the gods, and comets were the death of kings.
Asteroids, on the other hand, are something else. The most famous of all was the one that ploughed into the Bay of Mexico 65 million years ago. The crater, named Chicxulub - 'The Fire of the Beast' - is seen from space and about 1200km in diameter.
The size of the asteroid is estimated to have been 10-15km in diameter, and from its fiery entry through the atmosphere it heated the air and depleted the oxygen, which caused many lung-breathing species to suffocate, and the wall of water as this rock struck the water, estimated to be 2-3km tall, swept away all living things, including dinosaurs.
When the asteroid made contact with the seabed 3000m below, the explosion is estimated to have had a nuclear force of 100 billion nuclear bombs.
The asteroid explosion created a dust cloud that surrounded the Earth, blocking out the Sun and creating a nuclear winter.
Astrophysicists and geophysicists say if Earth was to be whacked by a similar size or larger asteroid, striking ocean or land, half of the world's population and animals would be wiped out.
Could we blow it up in space with a nuclear warhead?
No. If we did, billions of radioactive bits of rock would rain down on us, creating a deadly radioactive environment and life on this planet would be no more.