Ice sometimes forms into weird shapes, in one of the more bizarre examples it resembles candy floss and is referred to as “hairy ice”. This only occurs on certain trees on humid winter nights and scientists have only recently discovered how and why it forms.
Scientists have identified a fungus called Exidiopsis effusa that seems to be the final ingredient and is key to ice growing into thin hairs. The so-called “hair ice” only grows when the humidity is extremely high, approaching 100%, and the temperature is slightly below 0°C (32°F). The research is published in Biogeosciences.
Without the fungus, the ice will form just as a crust
“Hair ice is a way for the wood to get rid of water,” said coauthor on the study Christian Mätzler, from the University of Bern. “When wood lies on the ground it gets water from the rain and soil moisture. When it freezes the water inside [the wood] stays as a liquid, but it starts to freeze on the outside, the surface of the wood.” Their analysis supports a 100-year-old theory on where the ice came from.
Hair ice, first discovered by geologist Alfred Wegener in 1918, is remarkable, in that it can keep its wispy shape for many hours. “It may grow one night, and then continue the following night when it’s cool again,” said Mätzler. The phenomenon was found in Switzerland and Germany, but it can be seen in other forests with similar conditions.
As the ice grows on the outside it dehydrates the wood, which also protects the fungus inside from damage
And, for some unknown reason, this fungus then causes the ice to form in wisps. Mätzler said he didn’t know the exact science behind it, saying that “it is just a special idea of nature,” although recrystallization is thought to play a part.
A coauthor on the paper, Diana Hofmann from the Institute of Bio- and Geosciences in Germany, though, thinks that complex organic compounds called lignin and tannin may be at work. “These components may be the ones preventing the formation of large ice crystals at the wood surface,” she said in a statement.
But “the most surprising thing” was its shape, which can be 10cm (four inches) or more in length, with a diameter of 0.01mm (0.0004 inches), a ratio of one to 10,000. “This is extraordinary,” said Mätzler. “There are not many such elements that have this ratio.”
This is truly an interesting phenomenon, and certainly one that will have people interested.