Star Jelly: The Sky Slime That Science Keeps Failing to Name
The mystery is old enough to have a medieval name. Around 1314 the English physician John of Gaddesden, in his medical compendium Rosa Anglica, wrote of a substance he called "star slime," a jelly that people of his day believed had fallen from the heavens. Welsh tradition knew it as pwdre ser, the "rot of the stars." The tale barely changed for centuries: after a night of shooting stars, a farmer or walker would find a cool, translucent, quivering mass on the grass and conclude that a piece of the sky had come down with it.
The blobs themselves are not imaginary. They keep turning up, on the moors and hills of Scotland in the autumn of 2009, on lawns and fields around the world, usually after rain or in damp seasons. Colourless or faintly white, soft and gelatinous, they seem to appear from nowhere and melt away within a day or two, which only deepened their reputation as something not quite of this earth.
When scientists actually examine samples, the results are usually down-to-earth, if slightly grim. Many masses turn out to be the swollen remains of frog or toad spawn, a glycoprotein in the females' oviducts that soaks up water and balloons after the animal has been eaten and its innards left behind by a bird or fox. Others are colonies of Nostoc, a cyanobacterium that lies invisible and dry until rain makes it swell into green-brown jelly, or the fruiting stage of slime moulds.
What no analysis has ever supported is the part that makes the legend: the link to meteors. Shooting stars are specks of debris that burn up high in the atmosphere and leave nothing to land in a garden. The connection appears to be a trick of timing and imagination, people who go outside to watch meteors are simply more likely to be looking at the ground the next morning.
And yet the file is not entirely closed. A few samples resist every explanation. In one case a jelly submitted for testing was found to be mostly water, containing no DNA, no RNA and no cell structures of any kind, nothing that would identify it as spawn, bacteria or mould. Such results are rare, and often blamed on samples too degraded to read, but they leave a residue of genuine doubt.
So star jelly ends up in two piles at once: mostly a well-explained mix of amphibian remains and reviving microbes wrongly tied to the stars, and a small stubborn remainder that the laboratory simply cannot name. Centuries after John of Gaddesden, the honest answer to "what is it?" is still, for a handful of cases, that nobody quite knows.