Dale Andersen has traveled back in time. He’s been to Mars too. Or he’s come as close as possible without leaving terra firma. An astrobiologist for the SETI Institute, Andersen seeks out the world’s most inhospitable places—deep in the Arctic and the Antarctic, the Atacama Desert and the Mojave—to find the last thing you’d expect: life.

Andersen studies organisms called extremophiles, which thrive in hostile environments not unlike those that covered our planet more than 600 million years ago. “It’s like transporting yourself back to the Earth’s earliest biosphere,” Andersen explains. He’s discovered a moss that lives in a primordial soup with the same pH as grapefruit juice, and plants that manage photosynthesis from within ice-capped Antarctic lakes. With these species, Andersen is able to study the very limits of existence. They are far greater, he’s found, than we ever thought.

“If life manages to exist almost everywhere on this planet, what does that mean for Mars?” Andersen asks. “I’m just now beginning to figure out where this research is going to take us—how it informs future Mars missions.” He continues, “These are the building blocks for a whole new science.”