Ancient Microbes Carved Mysterious Tunnels in Desert Rocks Millions of Years Ago

Tiny, winding tunnels in desert marble and limestone have puzzled scientists for years. New research suggests these micro-burrows were carved by ancient microbes millions of years ago. Geologist Cees Passchier first uncovered the fossilised networks in the arid landscapes of Namibia, Oman and Saudi Arabia.

The burrows, too small to see without magnification, were likely formed by colonies of microbes rather than single organisms. Inside the tunnels, researchers found traces of biological material, along with calcium carbonate dust—a waste product commonly left by rock-dwelling microbes. The chemical makeup of the rock samples further points to a biological origin.

Liquid water would have been essential for the microbes to thrive and carve these intricate paths. While the exact type of microbes remains unknown, scientists suspect they were photosynthetic microorganisms, such as cyanobacteria. These same kinds of microbes still exist today, as ongoing studies of endolithic (rock-dwelling) organisms in deserts show.

Yet whether the specific microbes that made these burrows still survive—or if they died out long ago—remains unclear. The tunnels themselves suggest a thriving microbial world hidden beneath the desert surface millions of years ago.

The discovery sheds light on how ancient microbes shaped their environment through bioweathering. Though the mystery microbes behind the burrows are long gone, their fossilised tunnels offer clues about early life in extreme conditions. Scientists continue to study modern rock-dwelling microbes to better understand these ancient processes.