What does Pluto have on it?

Pluto is very like an extremely large, dirty snowball. Or like a snowy dirtball, depending on your perspective - Pluto’s about 50-50 rock and ice.

One thing Pluto does have in abundance is rather a lot of moons! Its most famous companion is Charon, which is about 10 times less massive than Pluto, but considering that our moon is only about 1% of the mass of the Earth, this is a rather large moon, relatively speaking. Pluto also has four other moons, named Nix, Hydra, Kerberos, and Styx. Kerberos and Styx were officially named just a few weeks ago - there was an online poll to suggest names for them, and these were among the most popular suggestions. (Vulcan was also an option, but the underworld theme prevailed.)

The only images that we have of Pluto are from telescopes both on the ground on Earth and in orbit. We base most of our information on what Pluto is based on based on how bright it is - the brightness tells us something about how much of the Sun’s light is reflected back at us. The more reflective the object, the more icy it has to be. If you look at the brightness of an object in various different wavelengths of light, you can get a sense of what color the object is, and whether there are irregularities in the surface. It turns out that Pluto has variations both in brightness and in color, which makes it a very interesting snowy dirtball. One would normally expect it to be roughly the same all over. It’s tricky to make these measurements from so far away, and ideally we’d like to send a probe to Pluto and take a bunch of pictures and measurements from close up.

Fortunately, in 2006, we launched a satellite to do just that - New Horizons. New Horizons is scheduled to fly past Pluto in 2015, hopefully expertly navigating all of Pluto’s moons and any other objects that might be hanging around near Pluto in 2015. New Horizons is packed with cameras and other instruments, so it should - if all goes well - be able to provide much more detailed maps of Pluto than we’ve ever been able to obtain before, along with measurements of the atmosphere of Pluto, and any rapid changes that may occur on the surface.

So keep your fingers crossed for New Horizons, and soon we’ll have a much better answer to what’s on Pluto than we do now!

Have your own question? Something here not make sense? Feel free to ask!