A number of movies have been made about what would happen if a large enough meteor collided with the Earth, such as the 10 km (6.2 mile) Chicxulub asteroid that struck the Yucatán Peninsula in Mexico around 66 million years ago, and is believed to be the caused the mass extinction of the dinosaurs. However, there are many places on the planet where one can find the rocky remains of space debris that made landfall without extinguishing life as we know it. This begs the questions–how routine is it for an object to collide with the planet, and just how worried should we really be about one causing catastrophic damage?
Meteors bombard the Earth thousands of times each and every year, producing meteorites, or the small rocky remnants of asteroids or comets that can be found all over the planet. According to estimates, somewhere between 18,000 and 84,000 meteorites weighing more than 10 grams strike the Earth per year, which at that size are usually so small that they do not cause damage. Furthermore, usually only those made from the stronger, denser material of an asteroid are likely to create a meteorite, while comets composed of rock, icy water and frozen gases are more likely to simply disintegrate. In addition, slower moving meteors are more likely to survive the Earth’s atmosphere and become meteorites, rather than ones travelling at greater speed.
Each year, stargazers look forward to witnessing a number of regular meteor showers in which space debris enters the atmosphere and is burned up before it can actually hit land or water, in the process producing some spectacular streaks of light across the night sky which we see on earth as a meteor or “shooting star”. It’s estimated that only 5 to 10 percent of all meteors successfully reach the Earth, and the majority of meteors that do manage to strike the surface end up in uninhabited rural areas or splashing down in the ocean. That’s why following an event like the Perseid meteor shower, we don’t find little pieces of space rock all over the earth.
Scientists say that the impact of the meteor itself isn’t really what would pose a threat to humans if a large enough one should succeed in making it all the way through the atmosphere. After the meteorite hits, it causes a shock wave that can travel for miles if the space rock is sizable.
In 2013, for example, an asteroid as big as a six-story building broke apart in the atmosphere about 15 miles (24 km) above the Earth’s surface producing a shock wave that was about equal in force to that of a 500-kiloton explosion. Around 1,200 people in Russia were injured as a consequence of the explosion and subsequent shock wave.
One of the most spectacular example of a large meteor explosion causing a frightening amount of damage occurred on 30 June 1908 near the Stony Tunguska River in Russia, where a 100 feet wide (30m) and 617,300 ton asteroid or comet exploded about 5 to 10 kms (3 to 6 miles) above the Earth’s surface. The resulting explosion is estimated to have been around 1,000 times more powerful than the atomic bomb that was dropped on Hiroshima, and the Tunguska event demolished 80 million trees over a 500,000 acres area of forest.
While the likelihood of a major calamity involving a meteor is rare, scientists do warn that it would be very difficult to know if one was approaching. Scientists are working in isolated areas, such as the Sahara Desert, to study meteorites, date them and look for patterns that might allow them to create predictive models that would put mankind in a better position to know whether there was ever an imminent danger.