the moon really is a harsh mistress
The coldest place in our solar system isn't somewhere in the outer reaches of the Oort Cloud. It's a network of craters on the Moon.
One would think that distant, frozen places like Triton or Pluto would have the coldest recorded temperatures in the entire solar system. And one would be wrong. Make no mistake though, these icy worlds aren’t exactly a balmy destination. The most bone chilling weather on our planet can kill an unprotected human in just a few minutes with a temperature of -128°F. Triton is more than three times colder than that at -391°F which would freeze your body as hard as steel within seconds. Compared to that, Pluto isn’t much worse. In fact, it’s about one degree warmer than the coldest place in our solar system, about 238,900 miles away. On the Moon.
According to the latest data from NASA’s new LRO probe, temperatures in lunar craters in places that can be very literally described by the expression “where the Sun doesn’t shine,” fall to a jaw-dropping -397°F which is uncomfortably close to absolute zero, or -459°F. It’s meaningless to talk about what would happen to a human body in this kind of cold since the very molecules holding it together would be on the verge of freezing in place. And when your molecular structure begins to freeze over, it’s a good sign that the thermostat is turned way too low. Technically speaking, it’s thought that attaining absolute zero in a natural system is highly unlikely due to various quantum phenomena and that laws of thermodynamics. (So far the coldest known temperature in the universe is estimated to be just two degrees warmer than the theoretical threshold of absolute zero.) But nevertheless, this may be about as cold as we can expect things to get around a G type star in its prime.
Now, you may be wondering how in the name of all that makes logical sense could we be flirting with -400°F temperatures just 93 million miles from the Sun where it’s nice and warm enough for liquid water to exist in abundance. Well, remember when I mentioned that there are places on the Moon where the Sun really never shines? These temperatures were recorded in craters that were actually embedded in bigger craters facing away from all sunlight. In this Russian doll-like arrangement of craters, the environment gets colder as time goes on, possibly trapping elements like water ice in the deep recesses of these dark craters and freezing them to the consistency of some metals. I suppose this just goes to show how much we still have left to learn about our nearest cosmic neighbors.