Granite monuments and rocks of the legendary Machu Picchu, the sacred city of the Incas, may disappear in the coming decades due to the multiplication of bacteria and algae that eat granite. This is what chemists and archaeologists say, who published an article in the journal Science of the Total Environment.
The Inca Empire was the largest and most powerful state in the New World before the arrival of the Spanish conquistadors there, covering the territory that is currently occupied by Peru, large regions of Chile and Ecuador, as well as small corners of Argentina and Bolivia. It arose around the beginning of the 13th century, and just 200 years later its population reached 10 million, and its area was at a record size at that time.
The Inca state is interesting from a historical point of view in that it did not have the typical features of all ancient and modern empires of the Old World. The Incas did not have the usual writing, code of laws, currency, metallurgy and counting systems, as well as "classical" feudal or despotic relations between the supreme rulers and their subjects.
In terms of its territorial structure, the Inca empire resembled a federal state - it consisted of 4 large regions and about 86 provinces, on the territory of which individual peoples lived with their own culture and characteristics of local government. Many of them joined the union voluntarily, while others were conquered by the Inca armies, however, in both cases, they were gradually assimilated by the "great culture" of the empire.
One of the first such "subjects of the federation" was the so-called Sacred Valley - a mountainous region adjacent to Cuzco, the capital of the empire, conquered by the Incas back in the first millennium AD. The symbol of her assimilation of this became the famous citadel of Machu Picchu, built by one of the last "sons of the Sun" a century before the invasion of the conquistadors.
Archaeologists, as Morillas notes, have long noticed that the condition of many artifacts and buildings on the territory of Machu Picchu has deteriorated markedly in recent decades. Many scientists began to associate their degradation with the fact that the surface of these monuments was covered with growths of microbes.
Other researchers, on the other hand, believe that they protect Machu Picchu from destruction by preventing rain drops and various corrosive substances in the air from interacting with granite. Morillas and his colleagues tested which of these theories is closer to the truth by comprehensively studying the state of the so-called "Sacred Stone", a kind of analogue of the Kaaba for the Incas.
Enlisting the support of the city's guardians, the scientists enlightened the artifact using a special microscope, collected microbial samples from the surface of the prayer stone and chipped off a microscopic fragment of the rock. Taking them to the laboratory, they conducted a "census" among the inhabitants of the "Sacred Stone" and studied its chemical composition.
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It turned out that both on the surface and in the inner layers of granite there were a large number of lichens, algae and cyanobacteria, decomposing granite and feeding on the products of its decay.
Their traces, as the researchers note, were found even at a relatively great depth, about 20-50 micrometers, which led to the stratification of the stone and its transformation into loose "dust". The problem is also added by the fact that the granite itself turned out to be quite porous, which makes life easier for microbes.
Now, Morillas noted, his team is conducting similar assessments for all buildings and stone artifacts in Machu Picchu. Scientists are trying to figure out how to protect them from further destruction, and are also looking for possible traces of whether the "invasion" of microbes was caused by some past unsuccessful attempts to restore them.
