Lire en français · Auf Deutsch lesen · Leer en español
In Chauvet Cave, in the Ardèche region of France, researchers used UV fluorescence spectroscopy to study the prehistoric drawings in Chauvet Cave without touching them. Their findings, published in the journal ACS Omega, describe a thin natural layer of calcite that may have helped protect these works, which are about 37,000 years old. The site, sealed behind a heavy steel door, remains one of the most fragile in Europe.
A cave sealed for millennia
About 37,000 years ago, groups of Paleolithic people entered what is now Chauvet Cave and left detailed drawings of the local fauna: cave bears, lions, bison and horses. These works rank among the oldest known cave art to date.
A prehistoric rockfall later closed off the cave's entrance, and the cavity remained unknown until its discovery in the 1990s. This long isolation resulted in exceptional preservation: the drawings, made with charcoal, were never exposed to visitors or to outdoor climate variations.
A non-contact analysis technique
To study the walls without damaging them, the team led by Philippe Walter, who directed this work, used UV fluorescence spectroscopy. This method reveals fluorescent mineral deposits, invisible to the naked eye, by illuminating the surface with ultraviolet light. The researchers sought to identify the layers that had built up on the drawings over time.
The fragility of the prehistoric footprints on the cave floor calls for strict precautions. A portable spectrometer was therefore placed on a protective walkway, about 2.5 meters from the wall, so as not to damage the floor or the traces it preserves.
The researcher compares his approach to a forensic investigation: every clue is examined to reconstruct the artists' techniques and understand how the paintings survived over time. The method requires no sampling, making it a suitable tool for a site as sensitive as this one.
A calcite varnish that protects the drawings
According to the study published in ACS Omega, mineral-laden water flowed over the limestone surface of the wall, leaving thin layers of calcite. Under black light, this calcite glows blue, revealing a natural varnish covering certain parts of the drawings. This mineral veil may have acted as lasting protection against wear.
Some areas also show orange fluorescence. It could come from hot charcoal or burning materials, such as a torch rubbed against the rock while the figures were being made. These observations suggest a subtle interaction between the people and the local geology, which allowed the works to survive for tens of thousands of years.
Applications well beyond archaeology
The authors of the study believe the technique could be used in other fields, from forensic science to monitoring biofilms aboard the International Space Station, a project already underway.
For heritage conservation, the benefit is also practical: it allows fragile works to be studied without contact or sampling, a crucial requirement for sites as sensitive as Chauvet, whose location remains confidential.
Seeing prehistoric art in France
Chauvet Cave is not open to the public, and its location remains secret. Replicas and exhibitions nevertheless allow visitors to discover its works, notably the animal figures that made it famous.
Cave art enthusiasts can also visit other decorated caves in France, some of which feature comparable artwork, which can be explored on archeo-logis.fr.
Frequently asked questions
Where is Chauvet Cave located?
Chauvet Cave is located in southeastern France, in a limestone cliff. Its location is kept secret to protect these particularly fragile drawings. The entrance is closed by a heavy steel door.
How old are the drawings in Chauvet Cave?
The drawings were made about 37,000 years ago by Paleolithic groups. They depict animals such as bison, horses and lions. A rockfall sealed them before their rediscovery in the 1990s.
What is UV fluorescence in archaeology?
UV fluorescence involves illuminating a surface with ultraviolet light, which makes certain minerals glow. It reveals deposits invisible to the naked eye without touching the artwork. It is a non-invasive method well suited to cave art.
How did calcite protect the drawings?
According to the study, mineral-laden water formed thin layers of calcite on the wall, creating a natural varnish. This deposit covered parts of the drawings, helping them survive for tens of thousands of years.
Sources
Original summary written with the help of artificial intelligence from the sources cited, checked automatically, then translated from the French original. Information and quotations belong to their authors. Read the French original.
