252-3: Methane on Mars and Earth
Why does the presence of massive quantities of methane on Mars make some scientists predict that bacteria live there? Because deep ocean bacteria on earth produce lots of methane, too, and we assume that life here follows the same rules as possible life elsewhere.
Both of these studies use methodological naturalism. Both studies ask questions about the evolutionary niches deep sea bacteria on earth or possible bacteria on Mars occupy. The first study, about methane on Mars, is also really controversial among scientists, while its underlying premise, the theory of evolution, is really not.