Venus has been very prominent in the early evening these last couple of months. It was the subject of a feature in the last series by Brian Cox on the Solar System. I was interested in the apparent "snow line" effect on the mountains of Venus. It's a kind of metallic frost. It has to be something that melts and evaporates at 460 Celsius at the lowest levels on Venus but solidifies at cooler temperatures with altitude. Brian Cox names lead sulfide as a possible candidate. Looking that up, I see a melting point of over 1000 Celsius. This must be at Earth's standard atmospheric pressure and will be different on Venus. This article names bismuth sulfide and tellurium as other possible candidates.
