Ancient Microbial Tunnels Discovered in Desert Marble and Limestone

Researchers from the University of Mainz identified tube-like structures likely created by microorganisms millions of years ago, though their origin remains a mystery.

The structures, found in Namibia, Oman, and Saudi Arabia, are approximately half a millimeter wide and up to three centimeters long, forming parallel bands up to ten meters in length.
Researchers hypothesize that microorganisms created these tunnels to access nutrients in calcium carbonate, but the exact organisms remain unidentified.
The tube-like formations are estimated to be one to two million years old and are not believed to result from geological processes.
The marble containing the structures likely formed from oceanic limestone deposits during the Gondwana supercontinent era, 500 to 600 million years ago.
Scientists are still investigating whether the microorganisms responsible for the tunnels are extinct or may still exist in some form.