Climate & Weather

What Is Red Rain?

Ancient Greek poet Homer was one of the first to write about red rain.

Ancient Greek poet Homer was one of the first to write about red rain. Images

by Contributing Writer Google

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.

Bad Omen

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.

Desert Sand

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.

About the Author

Based in London, Maria Kielmas worked in earthquake engineering and international petroleum exploration before entering journalism in 1986. She has written for the "Financial Times," "Barron's," "Christian Science Monitor," and "Rheinischer Merkur" as well as specialist publications on the energy and financial industries and the European, Middle Eastern, African, Asian and Latin American regions. She has a Bachelor of Science in physics and geology from Manchester University and a Master of Science in marine geotechnics from the University of Wales School of Ocean Sciences.

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