Tiny mice found mummified at the summits of Andean volcanoes appear to be living in the harsh environment, which resembles Mars more than it does Earth

By Meghan Bartels on October 23, 2023

Tiny mice found mummified on the peaks of Andean volcanoes had made a home in the Mars-like environment, new evidence suggests—as impossible as the feat would seem.

High in the Andes, tucked below the knee of South America’s western coast, is the Atacama Desert. One of the driest places on Earth, the regions is such a brutal landscape that NASA astrobiologists visit it to understand how they might search for microscopic life on Mars. Scientists had expected life at the summits to be limited to microbes, but it turns out that isn’t the case. Instead a new genetic analysis published on October 23 in Current Biology suggests that mice found living on the peaks aren’t outliers but representatives of a fairly persistent population.

“For miles around, it’s this really austere, Martian-like landscape, a hostile environment, and then the summits of these volcanoes are even more hostile,” says Jay Storz, an evolutionary biologist at the University of Nebraska–Lincoln and co-author of the new research. “When you experience these environments firsthand on the summits of these volcanoes, it’s just mind-boggling that [mammals] could be living up there.”

That’s why he and one of his colleagues were shocked when, near the top of the Andean volcano Llullaillaco in 2020, they stumbled on a living leaf-eared mouse (Phyllotis vaccarum) at 6,739 meters (more than four miles) above sea level. At that altitude, vegetation is scarce, winds are fierce, and the air contains half as much oxygen as it does at sea level. The mouse immediately claimed the title of the world’s highest-dwelling mammal known to science. “To trap a live mouse in an environment like that was just super, super shocking,” Storz says of the find. He decided to keep looking.