PAMPAS DE LA JOYA, Peru—As humans prepare to blast off to Mars, there is still the question of what they’ll eat once they colonize the red planet. Scientists who have traveled here to the Peruvian desert say they have the answer. Potatoes.

Researchers at the Lima-based International Potato Center and scientists at the National Aeronautics and Space Administration are studying which type of potato could be best suited for extraterrestrial farming to support a human settlement on Mars. If everything goes as planned, the Martian...