Signs of asteroid impacts across Earth can still be seen at sites in Russia, Australia, and South America, just to name a few. The scientific community agrees that asteroids have not only hit our little blue planet in the past, but very well may be what has caused numerous mass extinctions over the course of our planets evolutionary history. Some of the most notable asteroid impacts have occurred in the Yucatan Peninsula, 65 mya; in Argentina, 3.3 mya; and Arizona, roughly 50,000 years ago.
These dates seem so far in the past, that at times they may seem insignificant, but asteroid impacts have occurred in the era of man’s recorded history. 10,000 people died in 1490 CE, when an asteroid hit the city of Chi1ing-yang. Though no one died when an asteroid hit Siberia in 1908, the 1,200 square miles of trees destroyed was still devastating. Even closer to our own lifetimes, the asteroid Hermes, narrowly missed impacting earth in 1937.
The earth is constantly getting hit with asteroids, most of these range in size from a grain of sand to a softball. These asteroids appear as shooting stars and most frequently the bulk of these asteroid break up in the earth’s atmosphere. According to killerasteroids.org, a website founded by NASA, asteroids big enough to cause mass extinctions only impact earth about once every billion years. An asteroid would need to be between three and 10 miles across to hit with enough force to cause the global climate change which would cause mass extinction.
What they call “medium” asteroids, those which are about 980 to 1000 feet across, only impact Earth about every 50,000 years, and those asteroids which are about the size of a school bus, are around roughly every thousand years. These “smaller” asteroids, the ones that are not large enough to cause a full scale extinction, can still cause damage and may wipe out cities. This being said, they are infrequent and the odds of actually being killed by an asteroid are 1 in 700,000, these odds seem low because of the amount of people who would be killed by a substantial asteroid strike.
In 1980, when the first asteroid watch program was started in Arizona, and when the hypothesis of an asteroid wiping out the dinosaurs was proposed, neither was given the scientific credit they now have. As of 2000, NASA has a Near-Earth Asteroid Tracking System (NEATS) which collects data on large asteroids near earth. They currently believe that the number of asteroids near earth, which have a diameter of greater than half a mile, is only between 500 and 1,000. Previous estimates had this number doubled.
It is through organizations, such as NEATS, that Apophis was discovered. This asteroid, which is roughly 885 feet in diameter will pass very close to Earth in 2029, the again in 2036. The pass it will make in 2029 will not hit Earth and there is a 1 in 250,000 that the orbit will shift enough to hit Earth in 2036.
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