Number of words: 114

The small comets are giant, loosely packed “snowballs” with some kind of thin shell, made perhaps of carbon, that holds them together as they travel through interstellar space. But as they approach the electrically charged Earth, the electrostatic stress on these objects causes them to break up at an altitude of about 800 miles above Earth. Rapid electrostatic erosion appears to be the mechanism responsible for stripping the thin protective mantle from the water-snow core of a small comet. By the time the fragments of the comet have descended to about 600 miles, the “snowball” fragments have been vaporized by the Sun’s rays.

Excerpted from ‘The Big Splash’ by Louis Frank and Patrick Huyghe