Unusual geological formations discovered in the deserts of Namibia, Oman, and Saudi Arabia suggest that an unidentified microorganism once inhabited marble and limestone in these regions. Researchers observed minute vertical tunnels within the rock, which appear to have been formed by biological activity rather than natural geological forces.
"We were surprised because these tubes are clea by Robert Schreiber
Berlin, Germany (SPX) Mar 19, 2025
Unusual geological formations discovered in the deserts of Namibia, Oman, and Saudi Arabia suggest that an unidentified microorganism once inhabited marble and limestone in these regions. Researchers observed minute vertical tunnels within the rock, which appear to have been formed by biological activity rather than natural geological forces.
"We were surprised because these tubes are clearly not the result of a geological process," said Professor Cees Passchier from Johannes Gutenberg University Mainz (JGU), who encountered these features while conducting fieldwork in Namibia. Subsequent analysis of the samples revealed traces of biological matter, indicating that microorganisms had likely burrowed through the stone. "We don't currently know whether this is a life form that has become extinct or is still alive somewhere," added Passchier.
The discovery was made in the context of Passchier's long-term geological investigations in Namibia, where he has focused for over two decades on unraveling the structure of Precambrian rock formations to understand the assembly of the supercontinent Gondwana some 500 to 600 million years ago.
These marble formations, originating from ancient oceanic carbonate sediments transformed under heat and pressure, revealed the presence of peculiar parallel tube-like structures. Measuring around 0.5 millimeters in width and up to three centimeters in length, these tubes ran in bands stretching as far as ten meters and sometimes bordered by calcrete deposits. Their pattern diverged sharply from typical geological features and was first noticed 15 years ago.
In collaboration with Mainz University's Institute of Geosciences and Dr. Trudy Wassenaar of Molecular Microbiology and Genomics Consultants, Passchier has extensively studied these structures. "We think that it must have been a microorganism that formed these tubes." Notably, the tunnels were filled with finely ground calcium carbonate, suggesting the organisms extracted nutrients from the rock, leaving behind this residue. Similar phenomena were documented by Passchier in limestone formations in Oman and marble in Saudi Arabia.
Passchier estimates that these structures are at least one to two million years old and likely formed under conditions wetter than those of today's arid deserts. However, the specific nature of the organism responsible remains unresolved.
Endolithic microorganisms, capable of surviving within rock substrates by utilizing the minerals for sustenance, are known to inhabit extreme environments. "What is so exciting about our discovery is that we do not know which endolithic microorganism this is. Is it a known form of life or a completely unknown organism?" Passchier noted. The absence of light deep within the rock where these tubes are found suggests the microorganism was adapted to such conditions. Although biological material was detected, no DNA or protein remnants were identified.
Passchier urges experts in endolithic life forms to further examine the phenomenon. He emphasized its potential relevance to Earth's carbon cycle, noting that microbial activity within rocks could influence carbon release and thus the planet's CO2 dynamics. "This form of life, of which we do not know whether it still exists, could be important for the global carbon cycle. It is therefore essential that the scientific community becomes aware of it."
Research Report:Subfossil Fracture-Related Euendolithic Micro-burrows in Marble and Limestone
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