Alien Downpour: The Red Rain of India

News agencies have long been promoting a 2001 red rainfall as being of alien origin. What's the evidence?

by Brian Dunning

Filed under Aliens & UFOs, Cryptozoology, General Science, Urban Legends

Skeptoid #224
September 21, 2010
Podcast transcript | Listen | Subscribe

Trentepohlia algae
Lichen rich in Trentepohlia algae growing on rock
(Public credit: Wikimedia)

It was July of 2001 in the Indian state of Kerala, a land of great tropical loveliness. It has pristine beaches on the Arabian Sea, lush green valleys sloping into its hills, and everywhere are rivers, waterways, and jungle. Kerala is a land of perpetual green beauty, a true garden of Eden. And so how incongruous it was when the rains came, and rather than their normal deluge of clean, clear water, they came down blood red. For two full months through the end of summer, every time it rained, the land was drenched crimson. To this day, some believe it was an invasion of biological material from an alien world.

Superstition runs pretty deep in India, and it's hardly surprising that residents came up with all sorts of ideas about the cause. The rain was frequently described as blood, some taking it as a omen, others as a curse. Some feared it was a sign of Kaliyuga, an age in Hindu tradition characterized by wickedness, greed, and oppression. Many took it as portending the end of the world, and there was genuine fear. One supposedly scientific explanation suggested that a meteor must have struck a flight of bats in mid-air, atomizing them into a cloud of blood which then rained down.

But very quickly, meteorologists filled in the blanks with real science. Red rain had happened before, not just here but in other surrounding countries as well. Researchers noted similar red rainfalls in 1818, 1846, 1872, 1880, 1896, and 1950, including one described by Charles Darwin. Chemical analysis showed that the red rainwater contained carbon, silicon, calcium and magnesium. This gave scientists a clue, and they looked westward. A great cloud of dust, kicked up by high winds over the Rub' al Khali desert in Saudi Arabia, had been carried east across the Arabian Sea. The dust particles seeded great rainstorms above Kerala's steaming jungles, and thus the rain came down tinted red, and full of desert minerals. The Times of India reported that space scientists at the Vikram Sarabhai Space Centre had made this determination using satellite photography, and their findings were published two years later in 2003 in the peer-reviewed Indian Journal of Radio and Space Physics. Thus was the mystery solved to the satisfaction of most scientists.

But not to everyone's satisfaction. A few fringe researchers took a second, closer look, and they found something very different. Chief among these was Godfrey Louis and Santhosh Kumar, two physicists who were, at the time of the 2001 rainfall, at Mahatma Gandhi University in Kerala. They noted the same chemical breakdown as the others, but also discovered something else when they examined the red particles microscopically. They weren't just pieces of dust; they appeared to be living, biological cells. How and why could red cells fall from the sky?

Perhaps the cells themselves offered a clue. Louis and Kumar's most extraordinary discovery came when they used dye to stain the cells, to make it easier to study their interiors. They found that the cells had no nuclei, and no genetic material like DNA. This was an astounding revelation. Living cells with no genetic material? The red rain of Kerala didn't look like anything that could have come from Earth's own biosphere. It was, quite simply, life, but not life as we know it.

Louis and Kumar dug, and found a number of people who had reported a loud bang, distinct from thunder, at about 5:30 in the morning on July 25, about three hours before the first red rainfall. They concluded that this was the sonic boom of a comet that entered the atmosphere above Kerala and exploded, distributing its contents throughout the sky. By examining the patterns of the rainfall reports, Louis and Kumar calculated that their hypothetical comet had left an elliptical debris field 450 km by 150 km, consisting of fine red particles that then drifted down into the rain clouds.

Panspermia is what we call organic material moving from one world to another, usually through comet or meteor action. In fact, this is one of the theories for how life may have originated on Earth. In 2010 Louis contributed to a paper claiming that the red cells could have come from the Red Rectangle nebula, or another similar nebula, due to the close match in color between the Kerala cells' fluorescence behavior and the extended red emission from the Red Rectangle.

Louis and Kumar made their first publication of their finding on a web site in 2003, and have presented papers at conferences and in astrophysics magazines a number of times since. And every time, they've been the darling of the mass media, with major news agencies like CNN repeating their sensational panspermia story without critique. It's been trumpeted throughout nearly every consumer news publication, although curiously, almost nobody else in the scientific community (and certainly nobody from botanical circles) accepts Louis and Kumar's space spore explanation. This is of little consequence to the news agencies, but to anyone interested in learning about the red rain phenomenon, it should raise the question of other possible causes.

And it turns out that the red rain did have another possible cause, one that was determined quickly and quietly, without fanfare, within a week or two of the first rainfall. It was apparently so mundane that almost nobody paid attention, and even today, you have to dig past reams of panspermia reports to find it.

Very soon after the 2001 rainfall, Kerala's Centre for Earth Science Studies (CESS), which normally studies natural sciences of local importance such as water resource management, had taken a sample of the red rainwater and examined it microscopically. They immediately noticed that the particles appeared to be spores, and so they sent the sample to the government's Tropical Botanical Garden and Research Institute for identification. The spores were incubated and grown, then re-examined, and found to be those of an unremarkable, and extremely common, local algae called Trentepohlia. Trentepohlia is heavy with red-orange carotenoid pigments, so this identification came as no surprise.

Kerala's climate makes it perfect for lichen. Upon just about every tree and long-exposed surface in the region can be found at least some trace of lichen. Lichen is not a species of plant, it is in fact a symbiosis of algae and fungus. Much of Kerala's lichen is red-orange, getting its color from the Trentepohlia algae.

There was only one question not clearly answered, and that was what had caused such a huge population explosion of spores, enough to visibly color the rainwater. It is typical and expected for spores to be found in the atmosphere — we call them stratospheric spores — it was just an unusually large bloom of them. But it's important to remember that every bloom of algae is a different size, and the largest are going to be, by definition, unusually large. There had been plenty of rain that year and conditions were good. That some blooms are larger than others is the way nature works, it's not evidence that something unseen or unknown must have been afoot. The red rain has even happened several times since the famous 2001 fall, and the botanists have found the same Trentepohlia spores every time.

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As there was nothing inconclusive or ambiguous about the Institute's identification of the spores, it's not clear why Louis and Kumar later embarked on their own project to come up with their own identification of them, particularly since they were physicists and were completely outside of their specialty. Perhaps they simply hadn't heard the results, though it seems hard to believe that someone wouldn't have brought them to their attention. What is clear is that there was a significant difference between what Louis and Kumar saw when they looked at the spores, and what the botanists saw; and that's the presence of DNA. The botanists found it, Louis and Kumar did not; and as a result, they decided the spores must have been alien.

Searching for genetic material in algae spores is hard. It's much more difficult than with some other types of cells, in part because spores are impermeable to the dyes used to make the material stand out. Spores have extremely durable membranes, designed to protect them from harsh conditions. This makes them incredibly hardy, surviving extreme temperatures, physical abuse, dessication, chemical disinfectants, and even radiation. This is why the botanists at the Tropical Botanical Garden and Research Institute grew the spores in a culture before trying to examine them. If you can get them to germinate, you break that sturdy cell wall from within. It's then much easier to dye them, and the genetic material is then relatively simple to detect. Not being botanists, Louis and Kumar tried dying the spores without growing them; and as might be expected, the cell membranes remained intact and they saw no genetic material.

And so, to summarize the background of the finding that Kerala's red rain consisted of alien cells, we have a completely hypothetical supposition put forth to explain bad data resulting from a methodological error by scientists working outside their discipline. There never was any uncertainty about the algae among Indian botanists, there was only a week or two after the rainfall until what they suspected was confirmed; and yet, it's nearly impossible to find this true cause of the red rain in pop culture. Even today, the overwhelming majority of articles written about Kerala's red rain promote the extraterrestrial alien spore theory. Documentary films are still being made today that make no mention of the algae, but publicize only the sensational alien theory. News articles continue to parrot the misconception that the cells contain no DNA, continuing to quote only Godfrey Louis and the two or three other non-botanists whom he has managed to convince of his alien theory.

All too often, we give undue credence to incredible stories simply because they've been written up in a magazine or broadcast on the news. The red rain of India is one powerful example of the need to provide extraordinary evidence to support an extraordinary claim, and it fails that test. The story of the Trentepohlia spores may not be sexy, and it may not blow anyone's mind, but it's what happened. Stick with the explanations that fit into our understanding of the world, and with the consensus of the majority of specialists, and you'll be right far more often than you'll be wrong.

Brian Dunning

© 2010 Skeptoid Media Copyright information

References & Further Reading

Ahmadjian, V. The Lichen Symbiosis. New York: John Wiley and Sons, 1993. 78-80.

Farquhar, P. "Panspermia theorists say India's red rain contains life not seen on Earth." News Limited, 3 Sep. 2010. Web. 17 Sep. 2010. <>

McCafferty, P. "Bloody rain again! Red rain and meteors in history and myth." International Journal of Astrobiology. 21 Jan. 2008, Volume 7: 9-15.

Ramakrishnan, V. "Coloured rain falls on Kerala." BBC News. British Broadcasting Company, 30 Jul. 2001. Web. 15 Sep. 2010. <>

Reed, J. "Mysterious red cells might be aliens." CNN. Time Warner, 2 Jun. 2006. Web. 17 Sep. 2010. <>

Sampath, S., Abraham, T., Sasi Kumar, V., Mohanan, C. Colored Rain: A Report on the Phenomenon. Kerala: Center for Earth Science Studies and Tropical Botanic Garden and Research Institute, 2001.

Reference this article:
Dunning, B. "Alien Downpour: The Red Rain of India." Skeptoid Podcast. Skeptoid Media, 21 Sep 2010. Web. 9 Oct 2015. <>


10 most recent comments | Show all 21 comments

Jared D - yes, I really agree with you there. I find the same where I live, but not so much alien/paranormal. The news, though pretty good, always has a 'spin', 'bias', 'angle' or insinuation... but to be fair, lots of things wouldnt be newsworthy or exciting enough without the extra "sparkle". I take most with a grain of salt, and often just accept that its 'info-tainment'.

Julie, Sonoma, CA - thats an interesting observation you make. I'd never thought about it, but I thought about it all today, and I have to agree with Phil B's extraordinary answer, and extraordinarily excellant examples.
"Extraordinary" does seem redundant, but its such a catchy and meaning laden statement/assertion, and a great way to end (or/and start) a 'discussion', or take it up a notch.
Maybe someone else can suggest something...? :)

Jon, Auckland, NZ
September 22, 2010 10:04pm

Brad, how likely is the explanation when cultivating the "blood cells" caused them to grow into moss?

That doesn't sound like very likely evidence that they were blood cells to me.

Jared D., Fairport, NY
September 24, 2010 2:12pm

At the beginning of this podcast I instantly thought of tidal blooms and then when you said algae I did a mini cheer and clapped

Trentepholia .. . I will have to add that to my list of awesome protists.

Imagine, as a teaser for a documentary about awesome nature, "And an aglae bloom so big . . . so bizarre . . . the skies rained crimson as blood"

I had no idea that algae blooms could occur in the frickin stratosphere, causing rain that looks like blood and scaring the crap out of india. It's like the coolest of all magic tricks: Where a normal magician allows you to examine a card or other item before doing a trick so you know it's ordinary and untampered with, here you can look at the illusion under a microscope and the trick is immune to every scientific test you have if you don't know what to look for. It is the greatest prank and magic trick, as done by mother nature.

Imagine if we seeded clouds with Trentepholia around october to cause bloody looking rain . . . Because I love Halloween, that's why.

Trentepholia . . . yeeeaaah *big grin*

That is awesome, and anyone who says otherwise can be spanked with a wet noodle.

Jonath, Omnipresent
September 27, 2010 6:28pm

"Chief among these was ... Louis and ... Kumar, two physicists who" - sound like they should be on their way to White Castle. ;-)

Don't hate me because I'm beautiful!! :)

David Willoughby, Billings, Montana
October 19, 2010 2:26pm

sometimes even I get confused...

Henk van der Gaast, Sydney
November 21, 2010 3:44am

Actually there are differences btwn Trentepohlia spores and the red rain cells. Trentepohlia spores have flagella (not observed on the red rain cells) and spores cannot reproduce at temps above 100C, whereas the red rain cells can. These differences were discussed by Kumar and Louis. You have ignored the fact they considered and rejected the Trentepohlia spores hypothesis.

Stephen, Oxford
April 28, 2011 7:48am

Dear Stephen, (Oxford): There are no differences between the red rain "particles" and the Trentepohlia spores as you, Louis and Kumar claim. Louis and Kumar simply cooked the spores under high pressure, which induced simple AGGREGATION. Then, dishonestly, they call this innanimate physical precipitation as "biological growth", which is B.S. in the fith degree, so no self-respecting scientific journal dared to publish their rubish.

Louis' stubborn refusal after all these years to try culture correctly or even acknowledge that the particles are Trentepohlia spores and capable of germination and true biological growth and reproduction under basic algal culture media, is either a reflection of his extremely poor understanding of biology or a sad case of pathological science.

Please let me bring to your attention that his own collaborator, biologist Dr. Wainwright correctly cultured the spores to induce germination and growth and he obtained DNA (shock!!!) from them. What did Louis do? He dismissed his own collaborator, covered his ears and repeated his shameless mantra: "the spores have no DNA, the spores have no DNA..."

The discrepancy lies not in a single error by Louis, nor in his apparent ignorance of standard microbiology, but:
1) in his stubborness to apply the scientific method.
2) his unwillingness to even consider feedback from the true biologists.

It sounds to me like an issue of his integrity, not just bad science.

Paul, Wisconsin
October 5, 2012 11:00am

If you don't get bogged down in all the other details, one still seems unanswered. Can Trentepohlia (or any other for that matter) spores replicate at the high temperatures claimed?

".. the cells clearly reproduce at a temperature of 121 degrees C. .. By contrast, the cells are inert at room temperature."

Has this been independently confirmed? If so, how do you explain it?

Ronnie, Louisiana
September 26, 2013 8:07am

After following the developments and research into this phenomenon, I would have to agree with this being a classic example of blinkered and poor science.
However, the theory of panspermia being responsible for the establishment of life here on Earth remains the most likely possibility.

Dr Scott, Hastings, New Zealand
February 13, 2014 12:18am

um.. no..

Panspermia is still in the "I'll take anything" stage.

It would be really exiting if we could link proposed extra terrestrial bioforms to current life on earth. One of my colleagues was just such a person to make that presumption/posit with possible data.

The fact remains that we have far too many mechanisms to explore and rule out that a DNA-RNA life form arrived here and evolved in amongst all the many possible and verifiable posits that that could have just occurred here.

Panspermia can merely mean that simple molecules may have been made elsewhere and can also mean that "frozen bioforms" could have arrived on an asteroid or a comet..

There is a problem and it may never be solved.. Those molecules could have assembled anywhere.

and of course the "zinger"; so if it came from somewhere else (Mars is a good guess we suppose), we are still looking for a solution.. How did the earliest form of self replicating molecules assemble and "reproduce"?

Panspermia is still in the "I'll take anything" stage.

Mulga Gill, Sydney
June 16, 2015 1:18am

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