SPACE
Are Venus and Earth the only cloudy planets?
Gina O’Neil
■ Clouds on Earth are formed from water droplets and ice crystals. The only other planet in the Solar System with primarily water-based clouds is Mars, although these are generally very thin and wispy, and don’t often show up in photographs. But if we look beyond water, then any planet with an atmosphere can form clouds. The distinctive clouds enveloping Venus, for example, are composed mainly of sulphuric acid, while those on the gas giants – Jupiter and Saturn – are primarily ammonia. Yet another chemical, methane, is the main constituent of clouds on Uranus and Neptune, as well as Saturn’s moon Titan.