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Explosive-laden jet ski near Istanbul, allegedly Ukrainian, not a working maritime drone — Defense Express
The National Antarctic Science Centre reports.
"These are multi-layered snowballs, which usually have a void inside. They can be either very small — from a few centimeters in diameter, or quite noticeable — more than a meter in diameter, resembling bales of hay in a field," the report says.
Such a phenomenon is quite rare, including in the Antarctic, although it can be found not only there. This is due to the fact that the formation of snow "doughnuts" requires a number of weather conditions: two different layers of snow (frozen or covered with ice crust and fresh, loose), a temperature close to the ice melting point, a specific wind and slope.