Mysterious Compound Detected on Pluto and Titan
Something on Pluto and one of Saturn’s moons, Titan, absorbs light in a way unexplained by anything in spectroscopic databases.
No One Is Quite Sure Why Ice Is Slippery
A thin, watery layer coating the surface of ice is what makes it slick. Despite a great deal of theorizing over the centuries, though, it isn't entirely clear why that layer forms.