From 25 July to 23 September 2001, red rain sporadically fell on the southern Indian state of Kerala. Heavy downpours occurred in which the rain was coloured red, staining clothes with an appearance similar to that of blood. Yellow, green, and black rain was also reported. Coloured rain had been reported in Kerala in as early as 1896 and several times since then.
It was initially announced that the rains were coloured by fallout from a hypothetical meteor burst, but a study commissioned by the Government of India found that the rains had been coloured by airborne spores from a locally prolific terrestrial alga. Other explanations were proposed but not until early 2006 did the coloured rains of Kerala gain widespread attention in the popular media. A controversial conjecture that the coloured particles were extraterrestrial cells was proposed by Godfrey Louis and Santhosh Kumar of the Mahatma Gandhi University in Kottayam. No information to support the extraterrestrial hypothesis has been published since 2006.
The coloured rain of Kerala began falling on 25 July 2001, in the districts of Kottayam and Idukki in the southern part of the state. Yellow, green, and black rain was also reported. Many more occurrences of the red rain were reported over the following ten days, and then with diminishing frequency until late September. According to locals, the first coloured rain was preceded by a loud thunderclap and flash of light, and followed by groves of trees shedding shrivelled grey "burnt" leaves. Shrivelled leaves and the disappearance and sudden formation of wells were also reported around the same time in the area. It typically fell over small areas, no more than a few square kilometres in size, and was sometimes so localised that normal rain could be falling just a few metres away from the red rain. Red rainfalls typically lasted less than 20 minutes. Each millilitre of rain water contained about 9 million red particles, and each litre of rainwater was contained approximately 100 milligrams of solids. Extrapolating these figures to the total amount of red rain estimated to have fallen, it was estimated 50,000 kilograms of red particles had fallen on Kerala.
The brownish-red solid separated from the red rain consisted of about 90% round red particles and the balance consisted of protozoans and debris. The particles in suspension in the rain water were responsible for the colour of the rain, which at times was as strongly coloured as blood. A small percentage of particles were white or had light yellow, bluish gray and green tints. The particles were typically 4 to 10 µm across and spherical or oval. Louis's images with a scanning electron microscope showed the particles as having a depressed centre, suggestive of biological cell, especially red blood cells. At still higher magnification some particles showed internal structures.
Sediment (red particles plus debris) from the red rain was collected and analyzed by the Centre for Earth Science Studies (CESS) using a combination of ion-coupled plasma mass spectrometry, atomic absorption spectrometry and wet chemical methods. The major elements found are listed below. The CESS analysis also showed significant amounts of heavy metals in the red raindust, including nickel (43), manganese (59), titanium (321), chromium (67) and copper (55) (amounts in ppm).
Louis and Kumar used energy dispersive X-ray spectroscopy analysis of the red solid and showed that the particles were composed of mostly carbon and oxygen, with trace amounts of silicon and iron (see table).
|Element||Weight %||Atomic %||Standards|
J. Thomas Brenna in the Division of Nutritional Sciences at Cornell University conducted carbon and nitrogen isotope analyses using a scanning electron microscope with X-ray microanalysis, an elemental analyzer, and an isotope ratio (IR) mass spectrometer. The red particles collapsed when dried, which suggested that they were filled with fluid. The amino acids in the particles were analyzed and seven were identified (in order of concentration): phenylalanine, glutamic acid/glutamine, serine, aspartic acid, threonine, and arginine. He concluded that the results were consistent with a marine origin or a terrestrial plant that uses a C4 photosynthetic pathway.
At first, the red rain in Kerala was attributed to the same effect, with dust from the deserts of Arabia initially the suspect. LIDAR observations had detected a cloud of dust in the atmosphere near Kerala in the days preceding the outbreak of the red rain.
K.K. Sasidharan Pillai, a senior scientific assistant in the Indian Meteorological Department, proposed dust and acidic material from an eruption of Mayon Volcano in the Philippines as an explanation for the coloured rain and the "burnt" leaves. The volcano was erupting in June and July 2001 and Pillai calculated that the Eastern or Equatorial jet stream could have transported volcanic material to Kerala in 25-36 hours. The Equatorial jet stream is unusual in that it flows from east to west at about 10° N, approximately the same latitude as Kerala (8° N) and Mayon Volcano (13° N).
The colour was found to be due to the presence of a large amount of spores of a lichen-forming alga belonging to the genus Trentepohlia. Field verification showed that the region had plenty of lichens. Samples of lichen taken from Changanacherry, when cultured in an algal medium, also showed the presence of the same species of algae. Both samples (from rainwater and from trees) produced the same kind of algae, indicating that the spores seen in the rainwater could most probably have come from local sources.Although red or orange, Trentepohlia is a Chlorophyte green alga which can grow abundantly on tree bark or damp soil and rocks, but is also the photosynthetic symbiont or photobiont of many lichens, including some of those abundant on the trees in Changanacherry area.
The report also stated that there was no dust of meteoric, volcanic, or desert origin present in the rainwater, and that the colour of the rainwater was not due to any dissolved gases or pollutants. The report concluded that heavy rains in Kerala in the weeks preceding the red rains could have caused the widespread growth of lichens, which had given rise to a large quantity of spores in the atmosphere.
However, it could find no satisfactory explanation for the apparently extraordinary dispersal, nor for the uptake of the spores into clouds. It noted, for example, that prior to the first red rainfall there had been almost continuous rain for a period of eight hours. CESS responded ‘‘While the cause of the colour in the rainfall has been identified, finding the answers to these questions is a challenge.’’
Parts of the CESS/TBGRI report were supported by Milton Wainwright at Sheffield University, who, together with Chandra Wickramasinghe, has studied stratospheric spores. In March 2006 he said the particles were similar in appearance to spores of a rust fungus, later saying that he had confirmed their similarity to spores or algae, and found no evidence to suggest that the rain contained dust, sand, fat globules, or blood.
In 2003 Louis and Kumar, physicists at Mahatma Gandhi University in Kottayam, Kerala, posted an article entitled “Cometary panspermia explains the red rain of Kerala” in the on-line, non-peer reviewed arXiv web site. While the CESS report said there was no apparent relationship between the loud sound (possibly a sonic boom) and flash of light which preceded the red rain, to Louis and Kumar it was a key piece of evidence. They proposed that a meteor (from a comet containing the red particles) caused the sound and flash and when it disintegrated over Kerala it released the red particles which slowly fell to the ground. Their work indicated that the particles were of biological origin (consistent with the CESS report), not inorganic material and they invoked the panspermia hypothesis to explain the presence of cells in a supposed fall of meteoric material. Additionally, using ethidium bromide they were unable to detect DNA or RNA in the particles. Two months later they posted another paper on the same site entitled “New biology of red rain extremophiles prove cometary panspermia” in which they reported that
The microorganism isolated from the red rain of Kerala shows very extraordinary characteristics like ability to grow optimally at 300°C (572°F) and the capacity to metabolize a wide range of organic and inorganic materials.These claims and data have yet to be reported in any peer reviewed publication. In 2006 they published a paper in Astrophysics and Space Science entitled "The red rain phenomenon of Kerala and its possible extraterrestrial origin" which reiterated their hypothesis that the red rain was biological matter from an extraterrestrial source but made no mention of their claims to having induced the cells to grow. One of their conclusions was:
If the red rain particles are biological cells and are of cometary origin, then this phenomena can be a case of cometary panspermia.Panspermia is the hypothesis that life on Earth was carried here from elsewhere in the universe. Fred Hoyle and Chandra Wickramasinghe have been among the proponents of the theory, but it has not been accepted by most mainstream scientists. The paper in Astrophysics and Space Science prompted numerous articles in the popular media.
Samples of the red particles were also sent for analysis to Milton Wainwright at Sheffield University and Chandra Wickramasinghe at Cardiff University. Wickramasinghe reported in December, 2006 that “work in progress has yielded positive for DNA”, but the results have not yet been confirmed. The absence of DNA is key to Louis and Kumar's hypothesis that the cells were of extraterrestrial origins.
Wainwright is quoted as saying:
“There appears to be an increasing tendency among scientists to come up with wild explanations when asked by the press to comment on unusual, novel phenomena. A good example is provided by comments about the recent Indian red rain phenomenon."A correction was printed in The Observer regarding Dr. Wainwright's comment that the red rain lacked DNA. Dr. Wainwright asked in the correction to make clear that he currently had no view on whether the samples contained genetic material or not, and that it was physicist Godfrey Louis who held that view. The controversial research of Louis et al. is the only evidence suggesting that these organisms are of extraterrestrial origin.
Sainudeen Pattazh came to the conclusion that, "Regarding red rain, there was an argument that it was alien presence. But that’s just like science fiction. During 2001-02, [a] peculiar geological situation was prevailing in Kerala like caving in of wells and landslides.”
A study has been published showing a correlation between historic reports of colored rains and of meteors. In an interview The author of the paper, Patrick McCafferty, said:
Sixty of these events (coloured rain), or 36 percent, “were linked to meteoritic or cometary activity,” he went on. But not always strongly. Sometimes, “the fall of red rain seems to have occurred after an airburst,” as from a meteor exploding in air; other times the odd rainfall “is merely recorded in the same year as a stone-fall or the appearance of a comet.”
A possibly related incident occurred in February 2008 when small fish rained down on Kerala.
On 31 July 2008 An incident of red coloured rain occurred in the municipality of Bagadó, Chocó, Colombia. It has been reported that an individual took a sample of the rain to a laboratory and subsequently it was found to be "blood".