Red rain in Kerala

2007 Schools Wikipedia Selection. Related subjects: Recent History

Red rain in Kerala was a phenomenon observed sporadically from 25 July to 23 September 2001 in the southern Indian state of Kerala. Heavy downpours occurred in which the rain was primarily red, staining clothes and appearing like blood. Yellow, green, and black rains were also reported.

It was initially suspected that the rains were coloured by fallout from a hypothetical meteor burst, but the Government of India commissioned a study which found the rains had been coloured by spores from a locally prolific aerial algae. Then in early 2006, the coloured rains of Kerala suddenly rose to worldwide attention after media reports of a conjecture that the coloured particles are extraterrestrial cells, proposed by Godfrey Louis and Santhosh Kumar of the Mahatma Gandhi University in Kottayam.

The rain

Kottayam district in Kerala, which experienced the most intense red rainfall
Kottayam district in Kerala, which experienced the most intense red rainfall

The coloured rain of Kerala first fell on 25 July 2001, in the districts of Kottayam and Idukki in the southern part of the state. 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 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 shriveled grey "burnt" leaves. Shriveled leaves and the disappearance and sudden formation of wells were also reported around the same time in the area.

The colouration of the rain was due to red particles in suspension in the rain water, and 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 rainfalls typically lasted less than 20 minutes.

Initial report

Shortly after the first fall of the red rain, it was reported in the media that scientists at the Centre for Earth Science Studies (CESS) and the Tropical Botanical Garden and Research Institute (TBGRI) had determined that the particles colouring the rainwater were some type of spore. Then in November of 2001, commissioned by the Government of India's Department of Science & Technology, the CESS and TBGRI released a report which concluded that Kerala's rains were coloured by algae spores, which were successfully grown in medium into lichen-forming algæ of the Trentepohlia genus. This algae was found to be associated with lichens in 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 suggested 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 found no definite mechanism for the apparent extraordinary dispersal of the suspect spores, nor for the uptake of the suspect spores into clouds.

The authors of the report analysed some sediment collected from the red rains, using a combination of ion-coupled plasma mass spectrometry, atomic absorption spectrometry and wet chemical methods. The major elements found are listed below.

Major elements present in the dried sediment
Element Weight %
Al 1.00
K 0.26
Mg 1.48
Ca 2.52
Na 0.49
Fe 0.61
Si 7.50
C 51.00
P 0.08

The presence of aluminium and the very low content of phosphorus is puzzling because aluminium is not ordinarily found in living cells, while normally about 3% phosphorus can be expected in the dry weight of biological cells.

Conventional theories

History records many instances of unusual objects falling with the rain — in 2000, in an example of raining animals, a small waterspout 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, and its localisation to Kerala despite atmospheric conditions that should have seen it occur in neighbouring states as well.

Another 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 natural process would separate the red blood cells from white cells, platelets and other blood components. Red blood cells disintegrate rapidly in regular rainwater because of osmosis, but this was not evident with the red particles. Furthermore it would have to be a sizeable quantity of bats to cover a province of India.

More plausibly, the suggestion has been made that the red raindust was the result of incomplete incineration of chemical waste at the Eloor industrial zone, the particles being formed from microparticles of fly-ash or clay which coalesced around an aerosol of partly burnt organics as the incinerator plume cooled. The chemical composition of the raindust matches that of burnt organics plus clay; the fallout pattern matches with the prevailing winds; and various organic chemicals will form cellular structures which replicate in the presence of clay.

Extraterrestrial hypothesis

Another hypothesis was proposed in 2003 by Godfrey Louis and A. Santhosh Kumar, two scientists at Mahatma Gandhi University in Kottayam, Kerala. Having collected samples of the rainwater at many locations, Louis and Kumar claimed that the red particles did not look like dust but instead appeared to be biological cells. Chemical analyses indicate that they consist of organic material, and so they proposed that the particles 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 liter 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.

Energy dispersive X-ray spectroscopy analysis showed that the particles were composed of mostly carbon and oxygen, with trace amounts of silicon and iron (see table).

Elemental composition of red cells by EDAX analysis
Element Weight % Atomic % Standards
C 49.53 57.83 CaCO3
O 45.42 39.82 Quartz
Na 0.69 0.42 Albite
Al 0.41 0.21 Al2O3
Si 2.85 1.42 Quartz
Cl 0.12 0.05 KCl
Fe 0.97 0.24 Fe

A CHN analyzer showed 43.03% carbon, 4.43% hydrogen, and 1.84% nitrogen.

Louis and Kumar performed tests with ethidium bromide to see if any DNA or RNA was present in the red particles, but found none. Their results are published in the journal Astrophysics and Space Science.

Further tests on the particles were carried out at Sheffield University by Milton Wainwright, who 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. He also said, “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 at least one publication, see The Observer 12 Mar 2006 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 DNA and that it was physicist Godfrey Louis who is of that view.

A sample of the rain was also sent to Cardiff University for analysis by noted panspermia proponent Chandra Wickramasinghe. Wickramasinghe has reported that “work in progress has yeilded [sic] positive for DNA”.

Possible 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. Initial speculation by scientists in Thiruvananthapuram suggested that the red particles could be dust from a comet, but subsequent research found that they were Trentepohlia algae spores.

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 been dismissed by most mainstream scientists.

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