For other uses, see Red Rain. The coloured rain of Kerala began falling on blood orange red July 2001, in the districts of Kottayam and Idukki in the southern part of the state. Yellow, green, and black rain was also reported.

The particles in suspension in the rain water were responsible for the colour of the rain, which at times was strongly coloured red. India, where they separated the suspended particles by filtration. The red particles collapsed when dried, which suggested that they were filled with fluid. A single spore viewed with a transmission electron microscope, purportedly showing a detached inner capsule. 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 such lichens. The site was again visited on 16 August 2001 and it was found that almost all the trees, rocks and even lamp posts in the region were covered with Trentepohlia estimated to be in sufficient amounts to generate the quantity of spores seen in the rainwater.

The report also stated that there was no meteoric, volcanic or desert dust origin present in the rainwater and that its colour was not due to any dissolved gases or pollutants. TBGRI report were supported by Milton Wainwright at the University of Sheffield, who, together with Chandra Wickramasinghe, has studied stratospheric spores. In February 2015, a team of scientists from India and Austria, also supported the identification of the algal spores as Trentepohlia annulata, however, they speculate that the spores from the 2011 incident were carried by winds from Europe to the Indian subcontinent. 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. 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.

These claims and data have yet to be verified and reported in any peer reviewed publication. In August 2008 Louis and Kumar again presented their case in an astrobiology conference. The red cells found in the red rain in Kerala, India are now considered as a possible case of extraterrestrial life form. They can also be cultured in diverse unconventional chemical substrates.

The molecular composition of these cells is yet to be identified. Researcher Chandra Wickramasinghe used Louis and Kumar’s “extraterrestrial origin” claim to further support his panspermia hypothesis called cosmic ancestry. 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. The controversial conclusion of Louis et al. Louis’ only reported attempt to stain the spores’ DNA was by the use of malachite green, which is generally used to stain bacterial endospores, not algal spores, whose primary function of their cell wall and their impermeability is to ensure its own survival through periods of environmental stress.

Other researchers have noted recurring instances of red rainfalls in 1818, 1846, 1872, 1880, 1896, and 1950 and several times since then. The science fiction film Red Rain was loosely based on the red rain in Kerala story. It was directed by Rahul Sadasivan and released in India on 6 December 2013. Red rain could prove that aliens have landed”. JULY 28, 2001, The Hindu: Multicolour rain”.

Archived from the original on 6 September 2010. The red rain phenomenon of Kerala and its possible extraterrestrial origin”. Center for Earth Science Studies and Tropical Botanic Garden and Research Institute. Morning shower paints rural Kannur red”. Red Rain in Sri Lanka in 2012″. Sri Lanka to investigate the cause of red rain received in some parts”.