It may not technically be a planet any more, but Pluto's still proving an interesting object.
Ceres, also a dwarf planet, has bright patches on its surface that may, or may not, be ice.
Pluto has a dark band around the equator. Why? We don't know. Hopefully New Horizons' nine day flyby will tell us more about both Pluto and its companion, Charon. (Pluto has several other moons, but Charon and Pluto appear to be a binary system, so while it's generally called a moon, I think "companion" is better).
Pluto was discovered in 1930 (although later searches of earlier data reveal it had been sighted before but not recognized) by the Lowell Observatory. The observatory is no longer actively doing science, and its main scope is currently closed for renovation, but once it's finished, it will be made available to the general public and students doing projects as before. (Yes, I've looked through that scope). But we still don't know much about it.
Pluto's mass is about 0.2% of the Earth, but its albedo...reflectivity...is 1.3-2 times greater.
As of right now, we think that Pluto's surface is primarily nitrogen ice - and the blotchy pictures look ice-like to me. It probably has a rocky core under a mantle of ice. It may have liquid water at the core-mantle boundary. (Yes, this means that there's a slight, slight possibility of life, but it's unlikely there's enough energy to fuel it). Oh, and it has an atmosphere of nitrogen, methane, and carbon monoxide. A thin one, which tends to snow out at distant points of the orbit.
So, will New Horizons confirm this or prove us wrong? So far, it looks like an iceball to me...
What do you think?