The very mention of the term “blood rain” is enough to send shivers down some people’s spines. The Biblical-sounding weather phenomenon isn’t just fiction or myth, either: there have been recorded instances of blood-red raining falling over regions from the time of the Ancient Greeks up through today.
A recent event, in Kerala, India, in 2001, saw the freaky precipitation falling over the region for over a month, off and on. While science has a perfectly reasonable explanation for how this happens, sound explanations don’t make red rain any less freaky to behold!
Blood Rain in History
In ancient times, red rainfall was seen as a very bad omen. In some cases, observers would go into a panic upon seeing the bright precipitation, assuming it was actually blood. They would ascribe the bizarre sight to being a bad omen from the gods, or evidence that something terrible was about to happen.
Historically, blood rain events are earliest described by Homer in the Iliad, though this instance is completely rooted in Ancient Greek myth. The poet Hesiod later invoked this blood rain imagery to similar portend coming doom. The historian Plutarch later discussed the phenomenon, writing that it was common during the time of Rome’s mythical founder, Romulus.
Throughout the Middle Ages and until around the 1600s, many people in Europe described blood-red rain as a sign of ill-fortune. It wouldn’t be until at least the 17th Century that meteorologists attempted to offer a true scientific explanation for what caused the red hue to appear in rain.
Scientific Explanations
It’s hard to say what caused the red appearance of rainfall in antiquity, or, indeed, if these incidents ever actually happened. However, in the modern era, incidents of “blood rain” are understood to have a few potential origins.
The most common explanation for this phenomenon is that it is caused by the presence of the airborne spores of the green microalgae Trentepohlia. This alga is common in the water around Kerala, where the most prominent recent instance of blood rain was recorded. Interestingly, the research that revealed that red rain samples from Kerala contained this alga strain also revealed that it was a transplant from Austria.
This discovery showed researchers that it’s actually possible for alga to travel between bodies of water via cloud dispersal. This method of intercontinental microorganism dispersal was previously thought to only be capable of spreading fungi and bacteria, but the presence of the red rain in India led researchers to perform DNA sequencing on the algae found in Kerala.
Other Potential Explanations
Some scientists argue that Trenepohlia might not explain every instance of blood rain. These meteorologists have proposed that some recorded incidents occurred far from the algae’s natural range, and thus must be caused by other factors.
These factors could be related to red dust permeating the atmosphere, or even the presence of an aurora, like those observed in the North Pole. Whatever the case, the sudden appearance of blood rain is always a bizarre sight, even if it has a perfectly reasonable explanation!
