Daily Image

22-12-2021
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The beauty of winter - just around the corner

Submitter: Jorrit Siebenga
Description: Close to our Christmas holidays, it felt like a perfect time for a nature themed daily image.

The woods surrounding the ASTRON building are home to a fairly rare natural winter phenomenon, called ‘hair ice’, uniquely appearing in very specific circumstances. Only the dead and rotting heartwood (without bark!) of broadleaf trees, containing the fungus Exidiopsis Effusa, exposed to extremely high ambient humidity, and just a little frost with temperatures approximately between 0° and -4° degrees Celsius.

The released oxidation- and digestion energy of the fungus keeps the wood slightly warmer. The residual products of these internal chemical processes, carbon dioxide and water, are being pressed out by the ‘wood rays’ of the heartwood. (microscopically thin channels, perpendicular to the growth direction of the wood) The water freezes immediately when exposed to the outside temperature. This caused the hair ice to build up from below and reach a stunning thickness of only 20 microns (only one fourth the thickness of a human hair), but able to reach lengths of several centimeters.

For a long time this phenomenon was a mystery, or at least not completely clear to the natural science community, and it was only until 2015 for this hard-to-find winter scene to be fully scientifically explained.

The pictures are taken on the 21st of December, alongside the access road, just 100 meters before reaching the ASTRON premises.
Copyright: Jorrit Siebenga
 
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