On June 30, 1908, a large object, possibly a comet or loosely constructed asteroid, exploded above ground in the Tunguska region of Siberia, Russia. The object disintegrated before impact and left no crater but did destroy trees over a 21,000 square kilometer area (more than half the size of Rhode Island). Read more at the Tunguska site.

The force of the Tunguska event is estimated at 40 megatons of TNT or about 2,000 times the force of the first atomic bomb dropped in Hiroshima, Japan in 1945. The explosion was heard as far away as London, England.

Between July 16, 1994 and July 22, 1994 the fragments of Comet Shoemaker-Levy 9 impacted the upper atmosphere of Jupiter (image at right). This was the first time scientists observed such an impact anywhere in the solar system. Such an impact on Earth would have caused massive destruction. The effects on Jupiter were visible for over a year.

A very large number of small objects, or meteorites, enter the Earth's atmosphere each day and collectively amount to more than 100 tons of material. Most are very small and burn up almost immediately.

The largest meteorite ever found (called Hoba and found in Namibia in Africa) weighs 60 tons.

Sources:
Tunguska - The Cosmic Mystery of the Century
Meteors, Meteorites and Impacts - very informative site with many links
Barringer Meteorite Crater - Lots of information and a fun game too
Image Courtesy NASA/JPL-Caltech - Original page here

Page by: Sulem R