This is Pluto's atmosphere. Image: NASA
Imagine these questions, asked by an annoying child: "Why is the sky blue?" "Why is the water red?" Now imagine that they're taking place on Pluto, a place where both of those questions would now apparently be valid.
NASA's New Horizons probe keeps teaching us crazy things about Pluto, which as recently as earlier this year looked like a tiny speck in the best photos we had of it. Most recent discovery: Pluto has a blue sky and red water.
Unfortunately, NASA doesn't really have answers yet for the imaginary annoying Pluto child. It's notable that we're able to detect an atmosphere on Pluto at all, but we're not quite sure what it's made up of yet.
"A blue sky often results from scattering of sunlight by very small particles," Carly Howett, a New Horizons researcher, said in a statement. "On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger-but still relatively small-soot-like particles we call tholins."
Tholins also appear to be important when it comes to the newly discovered (frozen) water on the planet. There's lots of frozen... stuff on Pluto, but NASA doesn't know what makes up most of the frozen regions. Some of the surface is covered in water, however.
The dark red regions are frozen water. Image: NASA
"New Horizons has detected numerous small, exposed regions of water ice on Pluto," NASA noted in the press release. NASA doesn't know yet why water appears on some regions of Pluto and not others, but it notes that Pluto's watery regions are a deep red color.
"I'm surprised that this water ice is so red," Silvia Protopapa, New Horizons scientist at the University of Maryland, College Park. "We don't yet understand the relationship between water ice and the reddish tholin colorants on Pluto's surface."
The more we learn about Pluto, the more mysterious it seems.