This week, NASA reignited our hopes of finding alien life when it announced the first direct evidence of liquid water on Mars. But before we start indulging in fantasies of space crabs and reptilian beings, we ought to remember that Mars is a frigid world with a thin atmosphere. And that raises an obvious question: What sorts of life forms could actually live there?
Any life on Mars today is almost certainly microbial, but beyond that, we can't be sure of anything until we actually dig it up and study it. Still, we can make some educated guesses about the nature of Martian life, by taking a deep dive into some of the weirdest biology on planet Earth.