Kuiper Belt, a disk-shaped region of space, extending beyond the orbit of Neptune, in which a very large number of minor planets are in orbit around the sun. These bodies, called Kuiper Belt objects (or trans-Neptunian objects), are generally less than 200 miles (320 km) in diameter, although some are larger. Quaoar, discovered in 2002, has a diameter of about 800 miles (1,300 km). Astronomers believe Kuiper Belt objects are composed of rock and ice and that some become comets. The discovery in 1992 of the object named 1992 QB1 provided the first observational evidence for the existence of the Kuiper Belt. The region is named after astronomer Gerard Kuiper, who theorized about distant objects in the solar system.
Precipitation does fall from the clouds of other planets, but it's a little more exotic than the good, old-fashioned rainwater we get here on Earth. Imagine sheets of methane, sulfuric acid and, yes, even diamonds falling from the sky.
It wasn't so long ago that astronomers thought the universe contained normal matter, or baryonic matter, the base unit of which is the atom. But when it comes to the cosmos, there's always more than meets the eye. What else is hanging out in space?