The deluge of Plutonian data continues, and it reveals still more of the dwarf planet’s beauty.
Today, NASA has announced that the latest data beamed back to us from the New Horizons spacecraft contains the first color images of Pluto’s hazy atmosphere. It’s a beautiful companion image to the stunning parting shot that the spacecraft took back in July. The verdict? Look up into Pluto’s sky and it might remind you of Earth:
“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” Alan Stern, New Horizons principal investigator, said in a press release.
As if the hazes weren’t interesting enough — they extend much further above the planet than scientists expected and are filled with large molecules that eventually freeze and tint the planet’s surface red — we now know that the molecules within them scatter blue light like our own atmosphere does. When a child asks “why is the sky blue?” you can give the same answer for both cosmic objects.
On Earth, the blue sky is really just a scattering of blue light by the nitrogen in our atmosphere. The small wavelengths that compose blue light bounce off the small nitrogen molecules. On Pluto, the sprinkling of blue is also caused by relatively small particles, in this case something called “tholins,” akin to atmospheric soot.
It is this soot, formed when methane and nitrogen is broken apart by UV light and allowed to create larger chains, that eventually freezes and descends through the Plutonian air. Their distribution creates the layered hazes, and their deposition on the surface dusts Pluto in red.
The other big finding in this batch of data was that Pluto has deposits of water ice on the surface. New Horizons found the ice by looking at both visible and infrared images — you might have missed it if you were looking at color images alone. Areas identified with water ice corresponded to areas with bright red surfaces. The researchers aren’t sure why the ice is crimson, but they speculate that it has something to do with the tholins on the surface.
So while the answer to “Why is the sky blue?” now applies to Pluto, we can’t yet answer “Why is the ice red?” for any planet, dwarf or otherwise.