We thought it was rain, you know, because of the lightning, and we were all so thirsty. But when it started coming down, it turned out to be blood. Thick, hot blood. You couldn’t see, you couldn’t speak without getting a mouthful. We just staggered around, trying to get out of it. - The Hunger Games: Catching Fire
In the second part of the Hunger Games Trilogy, Catching Fire, the 75th Hunger Games (third Quarter Quell), takes place in the Clock Arena set up in the ‘Capitol’, the capital city of Panem - the erstwhile continent of North America. Between the first 2 hours of the day and night (1 AM to 2 AM & 1 PM to 2 PM), blood pours down from the sky, making it nearly impossible for anyone to see anything. On the 2nd day of the Quarter Quell, Johanna Mason from the 7th District of Panem walks out of the water completely drenched in blood - not something one would get to see every day.
Petrichor in the air, a chill breeze blows, and clouds begin to gather in the nearly postcard-perfect sky. The dazzling blue sky turns to a dull grey. What starts as tapping on the window eventually becomes a pitter-patter. Rain is such a beautiful thing, isn’t it? Now imagine droplets of bright scarlet falling from the sky - ‘Blood Rain’, the sight of which creates mixed feelings among the people. There are multiple theories related to the origin of the blood rain. In the most real sense, the rain must have a bright red colour to be considered blood rain. For this to happen, the concentration of the matter that gives the colour must be really high, and this is extremely rare. However, in the UK, the term is loosely applied to rain with various shades of yellow to red.
As dust storms develop in the Sahara - the largest hot desert in the world, strong winds blow over the vast sandy stretches. These winds pick up the loosely held sand and dust particles and transport them over hundreds of kilometres - so much so that the effect of a strong storm is felt in the United Kingdom, which is more than 3500 kilometres to the North. The dust cannot stay forever in the sky, can it? The ‘European Monsoon’ - westerly winds that blow over the warmer landmass from the colder Atlantic Ocean, pick up lots of moisture and bring it to the drier mainland. As the ambient air gets saturated with water vapour, clouds begin to form, resulting in heavy rainfall. This rain picks up all the specks of dust and sand suspended in the air and precipitates as blood rain. This weird rain results in houses, trees and other properties getting covered with a red coating, much to the residents’ annoyance. Such occurrences are more common in regions closer to the Sahara like Spain and France.
It is important to note that ‘blood rain’ is not a scientific term, but rather a phrase that goes way back in history - around 700BC in Ancient Greece (Archaic Period). One of the earliest mentions of the phenomenon in the literature is the epic Greek poem that recounts the incidents of the Siege of Troy in the Trojan War - Homer’s Illiad. The Ancient Greeks viewed the phenomenon as ‘divine intervention’. They believed that Zeus made the sky shower rain of blood on the battlefield as a portent of impending bloodshed. This extraordinary phenomenon was also corroborated by the works of Homer’s contemporary, Hesiod. Gaius Plinius Secundus, popularly known as Pliny the Elder was the author of one of the earliest encyclopedias - Naturalis Historia (Latin, Natural History). In his book, Pliny reported several cases of blood rain. Nearly a century earlier, during the reign of the Roman Emperor Julius Caesar, a statesman and Academic Skeptic, Marcus Tullius Cicero clearly rejected the idea of actual blood in the rain. In his famous work of De Divinatione (Latin, Concerning Divination), he linked the origin to ‘ex aliqua contagione terrena’ or ‘an early terrestrial contagion’.
In the southern Indian state of Kerala, during the first monsoon spell of 2001, between late July and late September, the residents of the state witnessed the extraordinary sight of blood rain on numerous occasions. One huge setback to believing the presence of actual blood in the blood were the reports of yellow, black and green rain filed by several witnesses. National Centre for Earth Science Studies (NCESS) in Thiruvananthapuram, the capital city of Kerala, analysed the rainwater and found that it had a neutral pH. Further analysis of metals revealed the abundance of Chromium (Cr), Copper (Cu), Manganese (Mn), Nickel (Ni), and Titanium (Ti). This led them to believe that the blood rain can be attributed to a meteor explosion. This was the consensus until spores were found in the particles, which led a lot of speculations about an extraterrestrial source of the spores.
In 2013, a couple of scientists from the University of Glamorgan, UK, worked on the samples to unmask the DNA, that was previously believed to be missing. Not long after, in a 2015 study published in Phylogenetics & Evolutionary Biology, it was established that the reason for the red colouration was the presence of a European species of subaerial micro-alga called Trentepohlia annulata. The algae belonging to the genus Trentepohlia are commonly found to be in a symbiotic relationship with a fungus to form a lichen. Algae reproduction generally occurs by either sexual reproduction (fusing of male and female sex cells) or asexual reproduction. While smaller algae resort to simple processes of cell division or fragmentation, the larger ones produce spores. What’s surprising is that the algae did not have an Indian origin - previously reported only in Austria. By comparing the Kerala variant’s DNA sequence with the Austrian variant, it has been established that there are very few differences. This points towards an inter-continental transfer of the spores - something unheard of.
Generally, bacteria and fungi are introduced across continents by the “cloud-over-ocean” mechanism that involves the active/dormant cells taking a piggyback ride on the clouds drift across an ocean (or sea). Applying the same principle to this peculiar case leads to a few problems. To begin with, there is no concrete evidence to prove the above mechanism. Further, it also raises the question of why there aren’t any occurrences in the other states along the western coast of India. More research is required to answer these questions and explain this phenomenon better. Let’s hope it rains blood more often.