Pluto Is Covered in Frozen Water. Lots of Frozen Water
Suck it up, East Coasters. Sure, Winter Storm Jonas dusted you pretty hard, but that’s nothing compared to the full-time ice situation on Pluto. With an orbital period of 248 Earth years, the little world’s winters can last decades. And no matter what season, Pluto has mountains of water ice. A new map from NASA shows a solid majority of the dwarf planet’s visible surface is covered with frozen H-Two-Oh.
That’s news to scientists. Before, to get an estimate of Pluto’s water ice, they compared the dwarf planet’s spectral signature (the soup of photons reflected by the planet’s surface) with a spectral template of pure water ice. Problem is, the water ice on Pluto is mixed up with ices of methane, nitrogen, and carbon monoxide—which kind of hides the actual H2O. The image to the left shows this fallacious five o’clock shadow of water ice.
NASA’s ice sleuths got the better picture (at top) by stitching together two images from New Horizons’ infrared imager. Rather than a flat image, the scientists had a digital cube of data, with cross sections representing a broad swath of the near infrared spectrum. In effect, this let them mute the non-water ice signatures, and amplify that of the water ice. The result is the robust beard of blue on the right.
In the new map, Sputnik Planum—the heart’s left lobe—is still relatively free of water ice. This makes sense given the prevailing hypothesis that Sputnik Planum is basically a gigantic glacier made of nitrogen ice, methane ice, and carbon monoxide. The same stuff is probably behind Pluto’s northern bald spot (keeping with this weird “water-is-hair” metaphor I’ve got going here). Called Lowell Regio, it too is mostly water ice free, though unlike Sputnik Planum, which researchers believe formed from a massive impact, scientists aren’t quite sure why this region is so bare.
Viewed from on high, that blue marbling looks pretty smooth. But water ice on Pluto is like rock on Earth—it forms everything from soaring, jagged mountains to sweeping, pitted valleys. The other ices are more volatile, and therefore vulnerable even to the spare sunlight that reaches Pluto’s orbit. Those ices play the role of snow—coating Pluto’s landscapes at various times during the planet’s long, cold winters. But if nobody is there to complain about the weather, does it really matter if the winter is long and cold?
Excerpt from –