Planetary scientist Nathalie Cabrol takes us inside the search for microbes on Mars, a hunt which counterintuitively leads us to the remote lakes of the Andes mountains. This extreme environment — with its thin atmosphere and scorched land — approximates the surface of Mars about 3.5 billion years ago. How microbes adapt to survive here may just show us where to look on Mars — and could help us understand why some microbial pathways lead to civilization while others are a dead end.