In July of 2001, something weird hit southern Kerala, India. Rain in places like Kottayam and Idukki turned red. The downpour made the streets look strange and unfamiliar, painting everything in a colour no one had seen before.
Sometimes the rain came down yellow, green, or even black, but the red was the most dominant and grabbed everyone’s attention. They didn’t last long, often under 20 minutes, and some folks reported hearing a loud boom or seeing a flash in the sky just before the rain started.
Trees began shedding their leaves, and wells behaved strangely; some appeared suddenly, while others dried up completely. Understandably, people were unsettled and wondered what could be causing such a bizarre event.
While Kerala’s red rain or Blood rain of 2001 was eye-catching, it wasn’t entirely unique. Similar events have been reported elsewhere in the world, and even within Kerala itself. The state has a long history of unusual coloured rains, with yellow, green, and black showers documented as far back as 1896.
For the locals in Kerala, those stories didn’t make it any less strange.
Amid the confusion, people came up with early guesses to make sense of it. Some suspected dust carried from far-off deserts, like those in Arabia, while others thought it could be ash from a volcanic eruption in the Philippines.
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Leaving the earth, some looked to the skies for a more cosmic explanation. One theory linked the rain to a meteor exploding overhead, especially since loud bangs and flashes were reported. As noted, Kerala had experienced coloured rains before, going back to the 1800s, so some examined those earlier events to see if they might offer any clues.
To investigate further, scientists in India stepped in. Two groups, the Centre for Earth Science Studies (CESS) and the Tropical Botanical Garden and Research Institute (TBGRI), tested the rainwater and found tiny red particles, with about nine million in a single millilitre.
Across all the rain, scientists estimated that the total amount of red particles was around 50,000 kilograms. It wasn’t chemicals or dirt; it was spores, tiny reproductive cells, from a local green algae called Trentepohlia annulata, which grows on trees and rocks.
But Godfrey Louis and Santhosh Kumar, physicists at the Mahatma Gandhi University in Kottayam, proposed a bolder idea: these could be microbes from space, carried by a comet that broke apart over Kerala.
Under the microscope, scientists saw that the particles were tiny, about 4 to 10 micrometers wide, thinner than a human hair and nearly invisible to the naked eye. They were round or oval, with a small dip in the center, and composed mostly of carbon and oxygen, with traces of silicon and iron.
Those elements are the building blocks of plants and living things, pointing to Earth rather than space. The Particles also contained amino acids, the building blocks of proteins, confirming a plant origin, and the rainwater’s pH was neutral, around 7, ruling out salts or ocean water.
Together, these observations strongly suggested that the particles were algae spores, not extraterrestrial microbes. Heavy rains earlier likely stirred up these spores, sending them into clouds before they fell back down.
Louis and Kumar claimed the particles could survive extreme temperatures and had no DNA, but later tests detected DNA, and their heat claims didn’t hold up. Most biologists were unconvinced, pointing to algae as far more plausible. Since Kerala’s red rains continue to tie back to local algae, the space theory lost traction.
Beyond the science, the red rain shook people up. News of the red rain quickly spread, and as the villagers grappled with fear and fascination, international outlets picked up the story, spreading the mystery far beyond Kerala.
The event even inspired a 2013 Malayalam movie called Red Rain. In it, a scientist, played by Narain, digs into strange cattle deaths and sky flashes, turning the real event into an alien invasion story that runs for about an hour and 40 minutes.
Though it’s fiction, the movie shows how the red rain stuck in people’s minds. The algae explanation makes the most sense, but the whole thing still feels like nature throwing a curveball.
It’s the kind of event that keeps you wondering what other surprises nature might have in store.