Re: Looks like the lake might have existed before the glaciers
At STP, even the purest water will freeze. However, adding a solute, such as a salt (or a water soluble alcohol) can lower the freezing point. This is why seawater can be colder than 32F, because the salt in solution in it prevents it from freezing at 32. It has to go down to about 28F for the concentration in sea water. It is important to know that there aren't little tiny salt crytals floating around in a brine. The salt actually ionizes into Na+ and Cl- ions that fly around between the H2O molecules and a few stray H+ and O- ions.
Likewise, steam doesn't need dust particles to condense around to become a liquid, although a little dust does help provoke condensation somewhat.