Abstract
When a probe flew by Pluto, it made a shocking discovery: the surface is young. Astronomers are still scrambling to explain why. Since it's discovery in 1930, tiny Pluto has been a mystery. Lying at the edge of the solar system far from earth, Pluto is visible only with large telescopes. Even then, it appears as a small, faint speck (as a professional astronomer, I've seen Pluto only a few times). In 2006 Pluto suffered the indignity of being demoted from the ranks of planets. Astronomers that year created a new class of objects, dwarf planets, to accommodate Pluto and a few other large asteroids. Pluto is now viewed as one of the largest of the trans-Neptunian objects, a group of icy asteroids orbiting the sun beyond the orbit of Neptune, the most distant planet from the sun.