LAST weekend we had the prospect of witnessing a meteor shower – sadly weather conditions put paid to that for many in the South East.

The Leonid meteor shower, named after the apparent origin of the meteors from the constellation Leo, promised a spectacular show of shooting stars.

Meteors, shooting stars and meteorites are a natural phenomenon, but in the past they have been seen as signs from the gods and the cause of at least one mass extinction that killed off the dinosaurs.

First of all we need to separate out what the differences are between meteors and meteorites. The leonids – the shooting stars – are meteors.

They are bright streaks of light that travel across the night sky. They originate from comet 55P/Tempel-Tuttle.

The comet was independently discovered twice, first by an astronomer called Ernst Tempel, in 1865 and then by another astronomer, Horace Tuttle in 1866.

Particles of dust and debris from the tail of the comet enter the upper atmosphere as the Earth orbits and passes through the remnants of the comet’s tail.

Friction causes the particle to heat up and they burn up in the atmosphere to provide the spectacular shooting star effect. The burning meteors travelling at about 44 miles per second. The path of the comet, itself in an orbit around the sun, means Earth passes through this dust trail every year but the comet takes 33 years to complete one orbit of the sun.

Meteorites are very different from the meteors of the leonids.

They originate mostly from the asteroid belt which is a region between Mars and Jupiter that contains millions of fragments of rock and debris left over from the formation of our solar system.

The asteroids vary in size from small fragments to the largest, Ceres, which is roughly spherical with a diameter of 590 miles, roughly a quarter of the size of the moon.

At least 16 of the asteroids discovered in the belt have a diameter of over 150 miles.

With millions of bits of rock, large and small, orbiting the sun occasionally they will crash into each other and their orbit will be changed, some will be flung out of the asteroid belt where they could be set on a path that would intercept other planets, including the Earth.

Small fragments commonly do find their way to earth as they enter our atmosphere they will heat up and many burn up. Others will find their way to the surface.

Those that do we call meteorites. Astronomers calculate that, on average, the Earth is hit by around 17 meteorites every day.

Luckily, vast areas of the Earth are covered by water, deserts or uninhabited areas. The chances of a meteorite strike in a major city or populated area is slim but not unknown.

In 2013 a meteor was filmed streaking through the sky above the Russian city of Chelyabinsk. It exploded 16 miles above the ground, but the shockwave caused thousands of windows to shatter.

People were injured, mostly by flying glass, but some reported a temporary blindness caused by an intense flash of light when the rock exploded into tiny fragments.

As the main rock did not hit the ground it was classified as a meteor rather than a meteorite, but the devastation it could have caused would have been much worse if it had not exploded so high in the atmosphere. That asteroid was undetected and took everyone by surprise.

There is plenty of evidence that Earth has been hit by large meteorites in the past. One of the most famous is the Barringer meteorite crater in Arizona. Between 5,000 and 50,000 years ago an iron meteorite, about 300 feet across collided with the Earth.

At 4,000 feet wide and 600 feet deep, it is one of the most impressive and easily recognised craters, but it’s certainly not the biggest.

The largest discovered crater is the Vredefort dome in South Africa, at 118 miles in diameter it was formed after an impact over 2 billion years ago. But there could be another contender for the largest.

Sixty-five million years ago Earth suffered a mass extinction which wiped out the dinosaurs along with 75 per cent of all known living species.

The cause is thought to have been an asteroid impact roughly where the bay of Mexico is today, in the Yucatan peninsula. The crater – which has not been fully mapped or explored – could be up to 180 miles in diameter.

Meteorites come in two forms, rocky ones and iron meteorites. While we have detection systems to try and track the larger asteroids, there is always a chance that some will be missed. Our atmosphere offers us some protection, but there’s no guarantee we won’t be hit again