Unknown life forms discovered living in marble and limestone rocks

In the scorching deserts of Namibia, Oman, and Saudi Arabia, scientists have discovered a curious feature in the rocks – thin, orderly tubes running through marble and limestone, possibly created by ancient microbes.

These structures don’t resemble any known geological process, and researchers believe they may be the work of an unidentified form of microbial life. If confirmed, this discovery could reshape our understanding of how life adapts to extreme environments.

The investigation began with scientists from Johannes Gutenberg University Mainz (JGU), who noticed the phenomenon during fieldwork in Namibia. Later analysis confirmed the presence of biological material inside the rocks.

“We were surprised because these tubes are clearly not the result of a geological process,” said Professor Cees Passchier of JGU, who first spotted the strange formations. “We don’t currently know whether this is a life form that has become extinct or is still alive somewhere.”

A puzzle millions of years in the making

The discovery was made in samples of ancient marble that formed when carbonate deposits were subjected to pressure and heat over hundreds of millions of years. The tiny micro-burrows line the edges of fractures inside the rock.

“We noticed strange structures in this marble that were not the result of geological events,” remarked Passchier.

The tubes are no wider than half a millimeter and can stretch up to three centimeters in length. They run parallel to each other in long bands, some spanning up to ten meters.

Highly organized patterns in the rocks

Unlike erosion patterns that are typically left behind by wind or water, these formations appear highly organized, and hint at a biological origin. In some places, crusts of calcrete had formed around the edges of the bands, adding to their uniqueness.

The phenomenon was first observed in Namibia 15 years ago, but more recent samples have shown similar features in rocks from Oman and Saudi Arabia. The tubes in Oman appeared in limestone, while those in Saudi Arabia were found in marble.

In every case, the tunnels were filled not with empty space, but with fine calcium carbonate powder – suggesting that the microorganisms may have extracted nutrients from the rock and left the residue behind.

Microbes that thrive in the dark

The research team from Mainz University collaborated with Dr. Trudy Wassenaar, head of Molecular Microbiology and Genomics Consultants, to explore the biological aspects of the formations.

They suspect the tubes were created by endolithic microbes – organisms that live inside rock.

These types of microbes, including bacteria, fungi, and lichens, are known to survive in some of the world’s harshest environments.

But there’s a twist: the structures are likely one or two million years old, and may have formed during a time when the desert climate was more humid. And while biological traces were found, the structures were too old to preserve any DNA or protein that could help identify the organism.

“What is so exciting about our discovery is that we do not know which endolithic microorganism this is,” said Passchier. “Is it a known form of life or a completely unknown organism?”

The tubes are located deep inside the rock, far from any light source, meaning the life form must have existed without sunlight.

Rock microbes and Earth’s carbon balance

While the exact identity of the tunnel-making organism remains unknown, the implications could be far-reaching.

Microbial life that interacts with rock can influence the global carbon cycle by breaking down minerals and releasing carbon.

Professor Passchier said that while we do not know whether this form of life still exists, it could be important for the global carbon cycle. “It is therefore essential that the scientific community becomes aware of it.”

If these microorganisms played a role in transforming calcium carbonate, they might have contributed to the Earth’s CO₂ balance in ways we don’t yet understand.

Their potential influence on long-term climate regulation highlights the need for further investigation.

For now, the mystery remains buried in the rock. But with further study, these tiny tunnels might one day tell a much bigger story.

The full study was published in the journal Geomicrobiology Journal.

Image Credit: ©: Cees Passchier

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