It is an impressive phenomenon that usually occurs in cemeteries or swamps. From time to time, mysterious bluish flames appear, which appear for a few seconds on the surface and then disappear without a trace. Today, scientists know that this strange fire is linked to the decomposition of the bodies of living beings. In this process, bacteria that metabolize organic matter produce gases that spontaneously combust when in contact with air. “There is a small explosion and the bluish flame is accompanied by a bang that scares anyone around”, says chemist Luiz Henrique Ferreira, from the Federal University of São Carlos (Ufscar). With all this, it is not surprising that the phenomenon feeds legends of ghosts, hauntings and lost souls. In Brazil, he gave rise to one of the first indigenous myths known: the boitatá, the huge serpent of fire that kills those who destroy the forests.
The will-o’-the-wisp was even described in 1560 by the Portuguese Jesuit José de Anchieta: «Next to the sea and the rivers, you can’t see anything other than the boitatá, the sparkling torch of fire that quickly attacks the Indians and kills them. you.»
flames from beyond Decomposition gases fuel the strange phenomenon
1. When a living being dies, several species of bacteria come into action to decompose the organic matter. In this process, two gases are produced, methane and phosphine, which will be responsible for the will-o’-the-wisp phenomenon.
2. Gradually, the concentration of these gases grows, for example, inside a coffin. This increases the pressure underground, causing the mixture to leak through small cracks and rise towards the surface, sneaking through the pores of the earth.
3. On the surface, in contact with the oxygen in the air, the two gases spontaneously combust, producing a bluish flame. Everything happens quickly and the flame does not last more than a few seconds.
4. For those close to the phenomenon, the instinctive reaction is to run. The problem is that this movement causes a sudden displacement of air, pulling the flame and giving the impression that it tries to chase the victim – like a ghost, a banshee or the boitatá of the Brazilian Indians.