The Comet of 1491
This one must have scared SO many people. At a little less than four times the distance to our satellite, the moon, this was by far the closest pass that has been ever recorded at the time. No one knows for sure just how big it was. Even more, little did our ancestors know how much more interesting things would turn out to be.
One of the most famous Earth closes calls ever, it turned out to be also a pipsqueak. For a very long time, scientists thought that a comet that was 60 meters in diameter exploded over Siberia with a force of as much as 30 megatons, or around 2,000 times stronger than the atomic bomb dropped on Hiroshima.
However, nothing solid really hit the planet. All the pictures of the flattened forest must have been really impressive. However, scientists re-evaluated the numbers and discovered that the comet might have been as small as 30 meters, and the blast might have had only 5 megatons. More simply put, much smaller objects might harm more than we ever thought before.
The Great Daylight Fireball of 1972
I think the name sums up everything we need to know. In fact, it doesn’t get clearer than this. The size estimates range from 3 to 14 meters in diameter, but it all depends on whether it was ice or rock.
Whatever it was, the object burned right through the atmosphere from Utah to Canada for a minute and a half. Luckily for us, the space rocks struck a glancing blow. If it was to hit the Earth directly, it might have blasted us with 1/2 a Hiroshima’s worth of energy.
2004 FH and 2004 FU162
At 30 meters in diameter and made out of solid rock, 2004 FH would be a thumper of Tunguska proportions, if it ever hits. In the right place, it might only destroy a city. As it was, it passed 43,000 kilometers above Earth, back in 2004. Only three weeks later, FU 162 came along. Astronomers discovered approximately at the same time as the 6-meter-in diameter rock, soared only 6,4000 km above Earth’s surface.