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Red rain in Kerala was a phenomenon observed over several weeks beginning in July 2001 in the southern Indian state of Kerala. Heavy downpours occurred in which the rain was bright red, staining clothes and burning leaves on trees.

A convincing explanation for the phenomenon has yet to be found. Initially it was suspected that, like many instances of coloured rain, dust transported from elsewhere was responsible, but the distribution of the red rain was patchy whereas a dust layer would be expected to give rise to evenly distributed coloured rainfall. Scientists at the Mahatma Gandhi University in Kottayam have proposed a far more outlandish theory - that the dust is in fact composed of organic matter of extraterrestrial origin. If this were to be proven, it would be the first direct evidence in favour of the theory of panspermia, which posits that life on Earth arrived here from outer space.

The rain

The red rain in Kerala first fell on 25 July 2001, in the districts of Kottayam and Idukki in the southern part of the state. As well as red rain, some reports suggested that other colours of rain were also seen . Many more occurrences of the red rain were reported over the following 10 days, and with diminshing frequency until the end of September.

The coloration of the rain was due to red particles in suspension in the rain water. When it fell, the red rain was at times as strongly coloured as blood. 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 red rain. Red rain falls typically lasted less than 20 minutes .

Conventional explanations

History records many instances of unusual objects falling with the rain - in 2000, for example, a small tornado in the North Sea sucked up a school of fish a mile off shore, depositing them shortly afterwards on Great Yarmouth in the United Kingdom . Coloured rain is by no means rare, and can often be explained by the transport of dust from desert regions in high pressure areas, where it mixes with water droplets. One such case occurred in England in 1903, when dust was carried from the Sahara and fell with rain in February of that year.

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 . However, this hypothesis could not explain certain aspects of the red rain, such as its sudden onset and gradual decline over two months, its localisation to Kerala despite atmospheric conditions that should have seen it occur in neighbouring states as well, and the unusual nature of the red particles, discussed below.

Another possibility was that the rain contained pollen, fungal spores or algae, which can be carried high into the atmosphere, but the appearance of the red particles did not correspond to any known microbe. Microbes would be degraded with long storage periods in non-sterile conditions, but this did not occur with the red particles.

A third theory is that the rain contained mammalian blood, a large flock of bats having been killed at high altitude, perhaps by a meteor. Some bat species in India live in very large communities. However, no bat wings or other remains were found raining from the sky, and no known process would separate the red blood cells from white cells, platelets and other blood components. Red blood cells disrupt rapidly in regular rainwater because of osmosis, but this was not evident with the red particles.

Less conventional explanation

A more radical explanation for the rains was proposed by Godfrey Louis and A. Santhosh Kumar, two scientists at Mahatma Gandhi University in Kottayam, Kerala. Samples of the rainwater were collected at many locations, allowing the red particles to be collected and analysed, and Louis and Kumar found that the red particles did not look like dust but instead had the appearance of biological cells. Chemical analyses showed that they seemed to consist of organic material, and the scientists proposed that the dust may be microbes of extraterrestrial origin.

Louis and Kumar's analysis found that the red particles were typically 4 to 10 µm across, spherical or oval in shape, and similar in appearance to unicellular organisms. On average, 1 millilitre of rain water was found to contain 9 million red particles, and the weight of particles in each litre of rainwater was about 100 milligrams. Extrapolating these figures to the total amount of red rain estimated to have fallen, Louis and Kumar calculated that a total weight of some 50,000 kilograms of red particles had fallen over Kerala.

Chemical analyses showed that the particles were predominantly made of carbon and oxygen, with small amounts of silicon, sodium, aluminium, chlorine and fluorine also detected. Louis and Kumar performed tests to see if any DNA or RNA was present in the red particles, but found none.

Possibly cometary origin

A few hours before the first occurrence of the red rain, a sonic boom was reported by residents of Changanasserry in Kottayam district, accompanied by a flash of light. Louis and Kumar suggest that this was caused by the disintegration of a small comet entering the Earth's atmosphere, and that this comet contained large quantities of the red particles. Observations show that 85% of the red rain fell within 10 days of 25 July, and Louis and Kumar suggest that this is consistent with the settling of red particles released into the upper atmosphere by a cometary break-up. An initial study of the red particles by scientists in Thiruvananthapuram suggested that they could be dust from a comet, but subsequent observations found that the particles did not look like dust under close scrutiny .

Louis and Kumar further suggest that the particles are cells and thus represent evidence of extraterrestrial life. If the particles are biological in nature and did originate in a comet, it would be the first evidence in favour of the theory of panspermia, in which life on Earth is proposed to have been carried here from elsewhere in the universe. Fred Hoyle and Chandra Wickramasinghe have been among the proponents of the theory but it has never found much of a following, being dismissed by most mainstream scientists. Further tests on the particles are currently being carried out at Sheffield University.

References

1. Ramakrishnan, Venkitesh (2001). "Coloured rain falls on Kerala". BBC. Retrieved Mars 6. {{cite web}}: Check date values in: |accessdate= (help); Cite has empty unknown parameter: |coauthors= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
2. Louis G., Kumar A.S. (2006), The red rain phenomenon of Kerala and its possible extraterrestrial origin, accepted for publication in Astrophysics & Space Science (PDF)
3. Lane, Megan (2000). "It's raining fish!". BBC. Retrieved March 6. {{cite web}}: Check date values in: |accessdate= (help); Cite has empty unknown parameter: |coauthors= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
4. Satyanarayana M., Veerabuthiran S., Ramakrishna Rao D., Presennakumar B. (2004), Colored Rain on the West Coastal Region of India: Was it Due to a Dust Storm?, Aerosol Science and Technology, v.38, p.24–26
5. Radhakrishnan, M. G. (2001). "Scarlets Of Fire". India Today. Retrieved March 6. {{cite web}}: Check date values in: |accessdate= (help); Cite has empty unknown parameter: |coauthors= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)

External links

• http://www.world-science.net/exclusives/060104_specksfrm1.htm World Science article
• http://observer.guardian.co.uk/world/story/0,,1723913,00.html Article in The Observer
• http://www.newscientist.com/channel/life/evolution/mg18925411.100 Article in New Scientist

• Anomalous weather
• Astrobiology
• Kerala