The mysterious matter behind stunning hair ice revealed
Thursday, July 23, 2015, 2:12 PM - You may have been lucky enough to come across this remarkable phenomenon on a walk through the forest. Scientists have discovered the missing ingredient behind 'hair ice.'
Hair ice grows on rotten branches of trees and resembles candy floss. It takes the shape of white fine, silky hair and usually develops during humid winter nights when the air temperature drops slightly below zero degrees, according to the European Geosciences Union (EGU).
Scientists in Germany and Switzerland recently discovered the fungus Exidiopsis effusa is responsible for its distinctive shape.
Published in the Biogeosciences journal of the EGU, the team confirmed the 100-year-old theory behind the origin of this beautiful spectacle through a set of experiments.
"When we saw hair ice for the first time on a forest walk, we were surprised by its beauty," said Christian Matzler from the Institute of Applied Physics at the University of Bern in Switzerland in a EGU press release. "Sparked by curiosity, we started investigating this phenomenon, at first using simple tests, such as letting hair ice melt in our hands until it melted completely."
Hair ice was first studied in 1918 after geophysicist and meteorologist Alfred Wegener suggested there was a correlation between fungus and wood. Swiss professor Gerhart Wagner studied more on hair ice 90 years later when he discovered treating the wood with fungicide or dunking it in hot water suppressed the growth of the ice, according to EGU. However, the species of the fungus and the weather formula had never been identified, until now.
Researchers studied examples of wood with hair ice collected in the winters of 2012, 2013 and 2014 in forests located in western Germany near Brachbach. Meanwhile, Matzler conducted experiments to further understand the physics of hair ice.
"Liquid water near the branch surface freezes in contact with the cold air, creating an ice front and 'sandwiching' a thin water film between this ice and the wood pores," the press release states. "Suction resulting from the repelling intermolecular forces acting at this 'wood-water-ice-sandwich' then gets the water inside the wood pores to move towards the ice front, where it freezes and adds to the existing ice."
The shape of the growing ice is dependent on the wood rays situated at the mouth of the branch. Without the fungus, the ice forms a "crust-like structure."
The reason why it took 100 years to figure this phenomenon out?
Hair ice is rare and short-lived. It is spotted mainly in broadleaf forests and grows mostly during the night and melts when the sun rises, according to the study. It is invisible in the snow and camouflages in hoarfrost.