Red rain, sometimes called blood rain, is a meteorological event that consists of red-colored dust particles falling like rain droplets. Winds draw up the particles from desert or other terrestrial environments. Hot air currents in the atmosphere carry them hundreds or thousands of miles before the dust falls to the ground. Observed since ancient times, red rain has generated many theories about its origins.
One of the first written accounts of blood rain, as red rain was called at the time, comes in Greek poet Homer’s epic "The Iliad" in the eighth century B.C. Zeus, the king of the gods, caused blood rain to fall as a warning about the slaughter that would occur during a coming battle. Roman historian Titus Livius Patavinus, known as Livy, wrote of a “shower of blood” that fell in 181 B.C. over a century before he was born. Interpreting this as a dangerous omen, the Roman city fathers of the time decreed the need for human sacrifice to appease the gods. Europeans continued to believe up to the 17th century that red rain was blood and a bad omen.
In the modern era, scientists interpret red rain as a rare but regular meteorological phenomenon. Such events are well documented in Europe as the transport of sand and dust from the Sahara Desert, the world’s largest desert, by air currents. Red rains are most frequent in Western Europe during the spring and can extend as far north as Scandinavia. The color, which can also be yellow or orange as well as red, comes from oxidized iron-bearing minerals in the desert sand.
In 2001, red rain that fell for two months over Kerala state in southern India showed no signs of dust or sand. The particles stained clothes and were also colored yellow, black, green, blue and brown. When examined under a microscope, the particles looked like cells. In 2006, physicists from Cochin University in India and Cardiff University in Britain suggested that the cells had an extraterrestrial origin. They proposed that a comet passing through the Earth’s upper atmosphere may have disintegrated and its fragments fell to Earth in the form of red rain.
Red rains containing cells also fell over southern India and Sri Lanka in 2012. Physicists at Colombo University observed that these were very regular atmospheric phenomena. An investigation by the Indian government that year concluded that the colored cells or spores originated from terrestrial and marine algae, in particular a lichen of the Trentepohlia genus. At the same time, the Sri Lanka Institute of Nanotechnology identified the presence of bacteria in the red rain belonging to the Trachelomona algae species.
- American Meteorological Society: The Map Room; Seasonality in European Red Dust ”Blood” Rain Events
- MIT Technology Review: The Extraordinary Tale of Red Rain, Comets and Extraterrestrials
- BBC: Who What Why; What is Blood Rain?
- Daily News: No Meteoric or Alien Connection with Red Rain
- The Local: Blood Rain Heads for Southern Sweden
- Lankasri News: Health Ministry Identifies Cause for “Red Rain”
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