The dissemination of spores of micro algae has been identified as the origin of the 'Blood Rain' phenomena, according to a new study by Indian and Austrian experts. Since 1896, reports of intermittent red-colored rain in portions of Kerala and Sri Lanka have been coming in. The most recent one occurred in 2013 over Kerala.
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Even laundry left out to dry in the rain becomes red, reminding one of human blood. Many theories have been proposed to explain this strange occurrence, some of which are unreasonable, such as a divine spell or alien involvement. According to the Huffington Post in 2012, this was caused by extraterrestrial life (aliens).
The presence of spores of a European species of green microalgae, Trentepohlia annulata, caused the red color in the rain, according to a recent study published in the journal Phylogenetics and Evolutionary Biology. Trentepohlia annulata was previously only reported from Austria, a Central European country.
The study proved that blood rain is just a method used by this alga to disseminate its spores (similar to plant seeds) over a vast region at once, allowing algae to colonize a large area quickly. The study found that the DNA sequences of this species from Kerala and those from Austria were quite similar — and that they evolve slowly, implying that the alga arrived from Europe not long ago. "The investigation confirmed the possibility that the introduction occurred by clouds over the ocean — a mechanism of intercontinental species dispersal previously recorded for bacteria and fungi, but first time for algae," stated Dr. Felix Bast of the Central University of Punjab.
Clouds dispersing over oceans are similar to intercontinental flights; spores of this alga from Europe are delivered to India via clouds that drift across the Arabian Sea.
But, if the spores made it all the way over the Arabian Sea to Kerala and Sri Lanka, why didn't the event happen in places like Gujarat and MP?
"We don't have any proof for this "clouds over ocean" concept, but probability is high because this is how Trentepohlia spores get transported," Dr. Bast responded in an email to this Correspondent. Although it is unclear how these lower stratospheric clouds arrived in Kerala, the aerial route from Austria to Kerala will not travel through other states such as Gujarat or MP. It could also be related to the monsoon, as Kerala is the first state where the SW monsoon meets Sri Lanka."
"I would imagine these spores were delivered to the clouds by wind," Dr. Bast says of how the spores get into the clouds. We intend to collaborate with atmospheric experts to collect samples of transcontinental clouds in order to determine what types of creatures they transport. The ultimate proof will be a meta genetic analysis of cloud air using High-Efficiency Particulate Air Filters, for which I'll soon be applying for a research grant from the Ministry of Earth Sciences." He went on to say that the microalga is completely harmless and that the "blood" rainwater is perfectly potable, even for vegetarians. The current study was the product of an international collaboration comprising academics from India and Austria, which was funded in part by an INSPIRE Faculty Award.