If you live in an area where frost covers car windscreens in a layer of ice, you may have marvelled at the delightful patterns on the glass.
In southern Tasmania this week, some motorists woke up to frosty conditions — and a stunning array of swirls, spirals and crystalline landscapes on their windows.
The ABC Hobart Facebook page invited the public to share their best photos of the phenomena, with the call out resulting in a number of images showing fern-like branches and what could pass for aerial photographs of mountain ranges.
So, what causes the patterns?
"The patterns are the result of very tiny imperfections in the glass, such as scratches, specks of dust and salt, or the residue from washer fluid," Chloe Moore from the Royal Meteorological Society told the BBC.
"These variations in the surface affect the way that the ice crystals form and branch out."
There you have it, a science-based reason to wash the car.
What does mathematics have to do with it?
Kai Carter, a meteorologist with Washington State University's AgWeatherNet team, said the shapes on windscreens looked like those in nature for a reason.
"An ice crystal is made up of two building blocks: hydrogen and oxygen. These hydrogen and oxygen atoms form a hexagon shape that is a kind of six-sided ring," Mr Carter told the university's Dr Universe blog.
"Even though we may not be able to see them with our eyes, these hexagon shapes can repeat in a pattern across the frosty surface of the window.
Mr Carter said should the "molecules run into something like a speck of dust, salt or even a bit of washer fluid … they may change their direction".
"In mathematics, we call this kind of thing a fractal design. A fractal pattern repeats itself at different scales. One other place you can also find fractal patterns in ferns. The fern frond looks like it's made up of little fern fronds, which look like they are made up of even smaller fern fronds."
As beautiful as the patterns were, once the novelty wore off, how to clear the car window became the main topic of conversation on the ABC Hobart Facebook page.
Frost veteran Nathalie Laurence wrote when she lived in a region with "long runs of hard frosts and had only street parking, I'd put cardboard under the window wipers".
Margot Jolly suggested drivers "turn on the car and the heater … then use an old credit card or something similar to scrape off ice".
"Hopefully the warming car will stop any reforming".
However, it was Jo Algie who offered the most sensible course of action.
You can keep on top of the frost forecast for any location in Australia, with the BOM's MetEye alerting when the right conditions occur and the forecast air temperature is below 4 degrees Celsius.
