Science / Medicine : Study of Pluto Yields Some Surprising Data

Scientists have puzzled for years over the nature of Pluto, the outermost planet in the solar system, and most of their theories have proven wrong.

Now, two scientists who have been studying the tiny planet’s composition have concluded that it is a very strange sphere indeed. So strange, in fact, that scientists who thought it might be an errant asteroid or an escaped moon from Jupiter or Saturn are clearly wrong, according to William McKinnon of Washington University in St. Louis and Steve Mueller of Southern Methodist University in Dallas.

Their research reveals that Pluto is so rocky and dense that it is unlike the moons of Jupiter or Saturn, and thus could not have begun there. And it is too icy to have been an asteroid, they said in a report published last week in the journal Nature.

So a planet it is, complete with its own moon, which is half as big as the planet itself. Where did it get such a large moon? The scientists conclude that the moon, Charon, was probably split off from Pluto in a violent collision with some other body many years ago.

Many astronomers are studying Pluto this year because Charon is orbiting the planet in such a way that the two are eclipsing each other when viewed from Earth, and that allows scientists to determine their dimensions and study their composition. For the record, Pluto is 1,393 miles in diameter; Charon is 694.