A Crash from Space – Meteorites that Land on Earth

What would happen if a meteorite landed on Earth that contained alien bacteria? That’s the starting point for my Moon Stealer series. Todays blog post is all about Meteorites.

Most of the particles that enter the Earth’s atmosphere are sections of comets or asteroids that have broken off, and survived the journey through space. Approximately 90% of these originate from comets and are, therefore, quite fragile. They disintegrate when they enter our atmosphere, appearing as a bright streak in the sky. The Perseid meteor shower is an example of an annual display that occurs when Earth passes through the trail of debris left by the comet Swift-Tuttle. The comet’s remnants are very delicate and enter our atmosphere as an ice-dust mix, normally burning up on contact.

Whenever a meteor survives its impact with the atmosphere and lands on our planet’s surface, it is then referred to as a meteorite. Most of these are pieces of asteroids, which are denser, making them more likely to make it through the atmosphere. They also approach Earth at a slower speed, meaning that they suffer less damage as they travel. A small number of the meteorites that have been retrieved have come from the moon or Mars. These particles most likely separated due to a collision with another object, and have travelled through space for many years before they make it to our planet.

It is estimated that thousands of tiny rocks land on the ground each year, with the majority ending up in areas that are not heavily populated and go unnoticed. Most of the meteorites that have been found weigh less than one pound. Despite their small size, they are capable of immense damage, due to the speed at which they travel. One of these moving at 200mph would be able to shatter a car windshield, or fall through the roof of a house. The greatest levels of damage associated with meteorites are caused by the shock waves they make as they break through Earth’s atmosphere. In February 2013, a meteor the size of a six-storey building entered Earth over Russia. The shock wave it produced broke apart the atmosphere for 15 miles, injuring 1600 people in the process.

Astronomers are mostly unable to predict meteorite crashes, as most them are too small to be detected when flying through space. Even the ones that are large enough to be tracked, are normally unpredictable and may change course repeatedly. Researchers have determined the approximate number of meteorites that land on the surface, by counting those that they find in remote areas where they remain undisturbed. They can tell when the rocks landed due to the weathering of their surfaces, and make their estimates based on these.

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