Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more . CNN  —  Heat-trapping methane may be best known for the dangers it poses to humans and Earth’s atmosphere, but in the dark depths of the ocean, the greenhouse gas is a nourishing meal for some of the world’s most mysterious creatures, new research suggests. Scientists say they have discovered three previously unknown, unnamed species of sea spider off