67P Churyumov-Gerisimenko is a very dirty snowball. Comets may have brought much of Earth's water. Ice, dust & tholins. Tholins are a sort of like a simple c

67P Churyumov-Gerisimenko is a very dirty snowball. Comets may have brought much of Earth's water. Ice, dust & tholins. Tholins are a sort of like a simple crude oil, thick tarry and orangy brown - very rich in primitive organics and amino acid precursors. Pluto is red with tholins. http://www.planetary.org/blogs/guest-blogs/2015/0722-what-in-the-worlds-are-tholins.html http://www.planetary.org/blogs/guest-blogs/2015/0722-what-in...