Meteors are more common than you think

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Meteors striking earth have played a large role in a number of action movies, often with planet-altering effects. A meteor is considered the prime suspect for the extinction event that made the dinosaurs extinct, and most people would be forgiven for assuming that a meteor strike would have cataclysmic consequences.

Meteor approaching earthHowever, this is not always the case, as was evident in the meteor strike that occurred on the border between South Africa and Botswana. A South African farmer saw a flash in the sky, but didn’t realise what it was until the next day when neighbours reported seeing a meteor. The farmer checked his security video, and found that it had recorded the meteor in the sky. Another farmer managed to capture the impact on his phone.

The impact came shortly after a meteor terrified Chinese residents in Yunnan province with loud, booming thunder-like noises. It is thought that these incidents were both from the same meteor.

NASA had detected the asteroid when it was as far away as the Moon's orbit. It appeared as a streak in a series of time-exposure images taken by the Catalina telescope in Tucson, Arizona. This information was then sent to the Minor Planet Centre in Massachusetts, where the possibility of an Earth impact was discovered. NASA's Jet Propulsion Laboratory then checked the data, and found a “high probability” of impact. Automated alerts were issued to the Planetary Defense Coordination Office as well as NASA's headquarters in Washington, but there was little anyone could do to stop the asteroid's rapid descent. Just a few hours later the ‘LA 2018’ asteroid hit.

An asteroid is a small rocky body that orbits the Sun. Most are found in the asteroid belt (between Mars and Jupiter) but they can be found anywhere. When two asteroids hit each other, the small chunks that break off are called meteoroids. If a meteoroid enters the Earth's atmosphere, it begins to vaporise and then becomes a meteor. On Earth, it'll look like a streak of light in the sky, because the rock is burning up. If a meteoroid doesn't vaporise completely and survives the trip through Earth's atmosphere, it can land on the Earth. At that point, it becomes a meteorite.

According to Johan Smit, chairperson of the Astronomical Society of Southern Africa (ASSA), there are daily occurrences of dust, rocks and other debris from space falling to Earth. About 200 tons of rocky materials enter the Earth’s atmosphere every day. Most burn out without being noticed. If you look at the night sky outside the city you can see shooting stars, or meteors, every few minutes. These are dust-size particles entering the upper atmosphere at speeds of over 30 000 km/h: so fast that the frictional resistance of the atmosphere causes them to start burning up.

Asteroid ‘LA 2018’  had an estimated size of around 3 m to 5 m in diameter, making it too small to cause serious damage. In contrast, the meteor seen over Chelyabinsk, Russia, in February 2013 was an estimated 20 m wide. It broke windows in six Russian cities and caused more than 1 500 people to seek medical attention, mostly due to injuries from flying glass.

While our local meteor impact wasn’t big enough to do anything like that, it was a spectacular sight to behold.

Image credit: Copyright: solarseven / 123RF Stock Photo


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