Strange extraterrestrial blobs of foul-looking jelly seem to have fallen to earth in some places recently, in scenes reminiscent of the 1958 science fiction film The Blob starring Steve McQueen, about an alien slime from space terrorising a town and devouring the population.
For centuries there have been reports of strange gelatinous material that was called pwdre ser (pronounced “poodra sair”), Welsh for star rot. Its origins were claimed as the remains of meteors, regurgitated frog spawn, a fungus, slime mould and much else. In 1679, the playwright and poet John Dryden wrote, “When I had taken up what I supposed a fallen star I found I had been cozened with a jelly.” And reports of the jelly blob crop up in all sorts of literature, such as Sir Walter Scott’s novel Talisman, when the hermit says, “Seek a fallen star and thou shalt only light on some foul jelly, which, in shooting through the horizon, has assumed for a moment an appearance of splendour.” People have reported finding the jelly all over the UK, in fields, gardens and on gravel paths. Across the world it has been found on mountains, near volcanoes and in the Arctic and Antarctic. The blobs of jelly can spring up after heavy rain seemingly from nowhere, and then just as suddenly vanish when it turns dry.
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But this mysterious slimy blob is not an extraterrestrial alien, meteor, plant, alga, fungus or animal, so what is it? The most likely explanation is Nostoc commune, a form of cyanobacteria with single cells that can string together into chains of cells covered in a gelatinous mass. Nostoc can photosythesise, fix nitrogen from the air, survive extreme cold or heat and when it is dry shrivels up into an inconspicuous mat that can survive in suspended animation for decades. Then when it turns wet it resurrects itself into a gelatinous glob. Cyanobacteria such as Nostoc are ancient organisms that some three billion years ago helped kick-start life on Earth as we know it by changing the atmosphere, taking up carbon dioxide and giving off oxygen, without which we would not be here today.
