What happens to the man’s spit? What decision does he make when this happens, and what does it reveal about him?

The man's spittle froze and broke mid-air.

As he turned to go, he forced some water from his mouth as an experiment. There was a sudden noise that surprised him. He tried it again. And again, in the air, before they could fall to the snow, the drops of water became ice that broke with a noise. He knew that at 50 below zero water from the mouth made a noise when it hit the snow. But this had done that in the air. Undoubtedly it was colder than 50 below.