Red rain and blood rain: what are they and why do they happen

Red rain is a rain that falls dyed scarlet red . Cases of colored rain have already been reported since 1896. One of the most famous cases of red rain took place in 2001 in the city of Kerala , in southern India, when this rain fell for two months. Scientists at one of the nearby universities were immediately interested in the phenomenon, which at first seemed like a case of contamination. Thus, several samples were collected and when they were observed under a microscope, they saw that it had neither sand nor dust, but red cells similar to some microbes, but without traces of DNA.

From then on, the theory was developed that these cells could be extraterrestrial and, although at first there was skepticism, it was accepted for publication in a scientific journal in 2006, and not only that, but they believe that these cells are are reproducing. It was commented that there was the possibility that a comet had disintegrated in the outer atmosphere and contaminated the clouds when they floated above the Earth

However, after these speculations, other researchers showed that the case was due to the spores of a green algae or free or symbiotic life with lichens. This alga belongs to the cyanotic green algae genus Trentepohlia and its spores are observed as red particles in the rain .

The phenomenon of red rain also occurred in a town in Zamora during 2014. After taking some samples it was concluded that they belonged to the alga H. pluvialis , a unicellular freshwater green algae, but which under stress conditions is capable of produce the pigment astaxanthin, which gives it a reddish tint. After confirming the presence of this alga, it was determined that the rainfall and winds of those dates came from the Atlantic. This finding was important, because in those days this alga was not found in nearby lakes or swamps, but its existence in North America was known, so its origin could be due to these North Atlantic winds.

The so-called showers of blood were known since the Middle Ages, when they were considered as harbingers of imminent human suffering. They were also mentioned in Homer’s Iliad, in the texts of Cicero and other writers and in the Renaissance they attributed them to divine power, but the truth is that, with current scientific knowledge, it is already known that these rains occur in Europe and are They relate to the desert areas of the African continent.

In the desert of the Sahara ‘s sand storms they are common and up to 70% of the generated dust moves across the Atlantic Ocean to areas of South America and Europe. Then, the dust masses are displaced by the wind currents of the lower and middle layers of the troposphere, affecting the eastern Mediterranean from spring, usually towards the end of summer a low pressure system appears in the Balearic Islands and it displaces this mass of dust to the west of the basin. Thus, countries such as Greece, Albania, Montenegro, Serbia, Bosnia, Turkey, France, the United Kingdom or Spain are affected by this dust from the Sahara. In these rains the sky becomes opaque and the quality of the air decreases. Once these rains mix with water droplets that contain enough iron oxide they turn reddish or orange in color. Researchers from the University of Arizona (United States) have reported more than 500 cases that have taken place since 1900.

In Spain people talk about mud rains. The State Meteorological Agency has already said that these precipitations are not polluting, they are alkaline and represent a benefit for vegetation and soils.

Although the red rains and the rains of blood have in common the coloration of the rainfall at the time of falling, the truth is that it is not the same phenomenon .

Rains of blood is a phenomenon that has been occurring for years in several European countries, including Spain, and is due to dust that is blown by the wind from the desert areas of Africa and mixes with drops of water. While red rains occur in Asian countries, such as India or Russia, and are due to red spore particles of an algae mixed with raindrops.