Unravelling the ‘Blood Rain’ Mystery

  • A recent study by Indian and Austrian scientists has led to the discovery of the cause of the ‘Blood Rain’ phenomenon to be dispersal of spores of micro algae.
  • Since 1896, reports have been coming in of sporadic instances of red colored rain over parts of Kerala and Sri Lanka.
  • The rain colors red even laundry left in the open to dry and reminds one of human blood. Many reasons were attributed to this mysterious phenomenon — some irrational — like a divine spell, and alien involvement.
  • The Huffington Post reported in 2012 that this was caused by extraterrestrial life (aliens).
  • The recent study, published in the journal Phylogenetic's and Evolutionary Biology , confirmed that the red color in the rain was caused by the presence of spores of a European species of green micro-algae, Trentepohlia annulata that was reported previously only from Austria —a Central European country.
  • The study confirmed that the blood rain is nothing but a mechanism employed by this alga to disperse its spores (similar to plant seeds) to a very large area at once, so that algae can quickly colonize a large area.
  • “The research confirmed the likelihood that the introduction happened through clouds over ocean — a phenomenon of intercontinental species dispersal previously reported for bacteria and fungi, but first time for alga” said the lead author, Dr. Felix Bast who works at the Central University of Punjab.
  • Clouds over ocean dispersal is analogous to the intercontinental flights that we take; spores of this alga from Europe get transported to India via clouds that drift across the Arabian Sea.
  • “We don't have any proof for this "clouds over ocean" hypothesis, but probability is high because this is how spores of Trentepohlia get transported. How exactly these lower stratospheric clouds got into Kerala remains unknown but aerial route from Austria to Kerala won't pass through other states like Gujarat, MP etc. It might be related to monsoon as well, as Kerala is the first state which the SW monsoon strikes together with Sri Lanka.”
  • “I would presume these spores might have got transported to the clouds by wind. We are planning to work with atmospheric scientists to sample intercontinental clouds to see what kind of organisms they transport. Metagenetic analysis of air from clouds using High Efficiency Particulate Air Filters will be the ultimate proof, for which I'll soon be applying for research grant from Ministry of Earth Sciences.”
  • He added that this micro-alga is absolutely harmless, and the “blood” rainwater is perfectly potable, even for vegetarians.
  • The present study resulted in an international collaborative effort involving researchers from India and Austria, supported in part by INSPIRE Faculty Award.