It was a cold night in Russia’s Sakha Republic. Tiny Oymyakon, widely regarded today as the coldest town on Earth, was used to going about its business in near-arctic temperatures. On February 6, 1933, its residents braved the lowest temperature ever measured in an inhabited location: ninety degrees below zero, Fahrenheit.*
In the most brutal corners of our planet, far from human settlement, the freeze is more intense. High on a ridge on the East Antarctic Plateau, in shadowy pockets explored only by satellite data, overnight temperatures bottom out around negative one-hundred and thirty-five degrees Fahrenheit. These are the coldest conditions ever recorded on Earth.
Earth, though, is a hospitable planet. For true frigidity, look to the outer solar system. Triton, an icy pink moon orbiting the gas giant Neptune, clocks in at nearly four hundred degrees below zero! On its surface, alien volcanoes blast their gaseous guts out in jets up to five miles high. The volcanic ejecta crystallize immediately and snow down to the frozen world far below. Evidence from Voyager 2 indicates that these giant plumes are mostly made up of nitrogen– the main ingredient in the air you’re breathing right now!
At three hundred and twenty-one degrees below zero, liquid nitrogen is colder than the most frigid Arctic night. It’s a cryogenic substance that would fit in with Triton’s weather better than our own. Nitrogen on Earth is usually a gas, but it’s possible to condense it into liquid form in the lab. As you can imagine, when air meets liquid nitrogen, its cools down fast. Water molecules in the chilled air condense into droplets visible as clouds or fog.
This might sound familiar! It’s closely related to the mechanism that causes clouds to form in the sky, a process we modeled in the lab not too long ago. Clouds are born when air cools down enough for suspended water molecules to condense. This is why you see fog when you push a warm breath from your lungs out into the atmosphere on a cold day, or when you bring something cold into contact with warm air.
Humid air, ripe with plenty of water molecules, produces extra-thick fog. Check out the cloud cover created by introducing liquid nitrogen into a damp poolside environment!