Don’t you just love cosmic coincidences? Today (Halloween), a comet with a very skull-like appearance is passing very close to the Earth – about 1.3 times the distance to the moon or just more than 300,000 miles. That may sound like a lot, but from a cosmic standpoint, it is very close.
As far as the rock, designated TB145, is concerned, it’s dead, meaning anything that could shoot out or boil off when it passed close to the sun, is gone. This particular asteroid is good sized, measuring between 1000 and 2000 feet across, depending on what telescope’s data you use. As for color, it’s a shade of asphalt, which is still brighter than most asteroids.
How unusual is it that a comet passes this close to the Earth? According to the JPL Near Earth Object Program, there have been 36 other objects that have passed as close or closer than the skull comet in the last year. Some have passed significantly closer, the closest being about a tenth the distance or about 30,000 miles.
How about Earth impacts? Small objects impact the Earth every day. Most of them either burn up in the atmosphere or fall harmlessly to the ground. Some, however, are larger and cause damage. One of the best documented and largest known was the Tonguska Event, where a large object struck a remote part of Russia in 1908. Estimates put its size at about 197 – 623 feet, much smaller than the skull comet. It didn’t make it to the ground. Instead, it exploded in a massive air burst at an altitude of 3-6 miles that leveled 770 square miles of forest. It had the force of about 15 megatons of TNT, or 1000 times the destructive power of the Hiroshima nuclear bomb. Again, this from an object less than half the size of the skull.
There have been other events as well. One, the Chelyabinsk meteor, was captured in photos and on video. It was estimated to have released energy equivalent to 500 kilotons of TNT – about 1/30th of the size of Tunguska.
Another possible impact, this one with deadly consequences, took place near Peshtigo, Wisconsin on October 8th, 1871. I say possible, because this is a theory and has not been proven. In this event, more than 1500 people died in fires. This date might sound familiar, as it is the same date as the Great Chicago Fire and other lesser-known fires in the cities of Holland and Manistee, Michigan. Fires raged in a radius centered roughly in the middle of the part of Lake Michigan, near Chicago. Again, this is just a theory, but it is very interesting.
So in recent history, only one documented strike has occurred that caused significant damage (Tunguska). The only other one is a possibility and a theory. It seems possible that we might see another such event in our lifetimes.