Blood rain

There is now a scientific consensus[1] that the blood rain phenomenon is caused by aerial spores of green microalgae Trentepohlia annulata.

In the 19th century, blood rains were scientifically examined, and theories that dust gave the water its red colour gained ground.

The earliest literary instance is in Homer's Iliad, in which Zeus twice caused a rain of blood, on one occasion to warn of slaughter in a battle.

[4] Unusual events such as a rain of blood were considered bad omens in Antiquity, and this belief persisted through the Middle Ages and well into the Early modern period.

[8] Gregory of Tours records that in 582 "In the territory of Paris there rained real blood from the clouds, falling upon the garments of many men, who were so stained and spotted that they stripped themselves of their own clothing in horror".

[9] Although the work of Geoffrey of Monmouth, a 12th-century writer who popularised the legends of King Arthur, is regarded as "fantastical" rather than reliable,[10] he too notes the occurrence of blood rain, in the reign of Rivallo.

This event was further expanded on by Layamon in his poem Brut (written around 1190), who described how blood rain was one of several portents, and which itself led to destruction:[11] In the same time here came a strange token, such as before never came, nor never hitherto since.

Afterward here came an evil hap, that king Riwald died.Many works which record occurrences of blood rain, such as that of Layamon, were written significantly after the event was supposed to have taken place.

The 14th-century monk Ralph Higden in his work, the Polchronicon, recounts that in 787 there was a rain of blood, perhaps intended by the author as an indication of the coming Viking invasion.

While some of his advisers thought the rain was an evil omen, Richard was undeterred:[15] the king was not moved by this to slacken one whit the pace of work, in which he took such keen pleasure that, unless I am mistaken, even if an angel had descended from heaven to urge its abandonment he would have been roundly cursed.

[17] The phenomenon gained exposure to a wide audience in the 16th century, during the Renaissance, when it was used as an example of the power of God; a form of literature using prodigies such as blood rain as cautions against immorality proliferated across Europe having originated in Italy.

Although his theory would later be rejected, he helped the likes of Pierre Gassendi and René Antoine Ferchault de Réaumur to lay the foundations for removing superstition from explanations of the phenomenon.

The research confirmed the likelihood that the introduction happened through clouds over the ocean, a phenomenon of intercontinental species dispersal previously reported for bacteria and fungi but not for an alga.

He concluded that blood rain was caused by water mixing with a reddish dust, mostly composed of animal and vegetable matter.

[25] This explanation has persisted, and the Academic Press Dictionary of Science and Technology (1992) attributes the colour of blood rain to the presence of dust containing iron oxide.

[33][34][35] Coloured rain was also reported in Kerala in 1896 and several times since,[36] most recently in June 2012,[37] and from 15 November 2012 to 27 December 2012 in eastern and north-central provinces of Sri Lanka.