in modern astronomy.Whatever your view, Pluto is more than just a Mickey Mouse character. But the Pluto we're talking about is not much bigger, at just 1,485 miles (2,400 kilometers) across, in the relative scheme of things. And because it's so far away -- 39 times as far from the Sun as Earth on average -- Pluto is also the
regularly moved in front of Pluto from our point of view, during its orbit. By observing a dip in the amount of sunlight reflected from Pluto in each of these orbits, researchers long ago made crude maps of the planet's "albedo," or brightness, providing clues to Pluto's surface structure and composition. The new map was made with the same technique. Young explained the process:
"Imagine your friend holding up a black-and-white checkerboard. He's too far away for you to see anything except a grayish blob, but you can keep track of the blob's brightness with your handy blob-light-meter. Now your friend calls you and says, 'I'm covering up the first square.' You notice that the checkerboard's brightness drops by about 1.5 percent, which means that the square (only one sixty-fourth of the total checkerboard) must have close to 100-percent reflectance. If, on the other hand, your friend says, 'I'm covering square number 2' and the brightness barely drops at all, then square number 2 must be pretty dark."
New insight
Because of the way Pluto and Charon orbit each other, only a portion of one side of Pluto can be mapped using this method. In the 1990s, researchers learned that Pluto's bright areas are a frosty mixture of nitrogen, methane and carbon monoxide. A weak signature of water was also spotted.
But no one has been able to discern what makes up the dark areas. Now Young says they may be an overlying layer of more complex molecules.
The colors on the map have been added by the researchers to illustrate certain features, so areas that are more reddish tell one story, and those that are grayer tell another. These false colors could help researchers figure out the relative ages of different parts of Pluto's surface, as well as what conditions were like in the "atmosphere" in which the surface formed.
"If the surface is red [or reddish], it probably contains some hydrocarbons that formed in that atmosphere (not unlike the Los Angeles basin) or in the surface," Young told SPACE.com. "If the surface is less red, it could be a very recent frost deposit (and hence very bright as well) or it could be colored by hydrocarbons that have undergone more extensive processing by the Sun's ultraviolet radiation and charged particle bombardment."
More radiation is thought to produce hydrocarbon molecules that appear as gray or black in the image, rather than red. All of this information might help researchers figure out where Pluto was when it formed, and what processes shaped its present composition.
And in the
advertisement
