As it turns out, sweltering Venus - average temperature a balmy 464 °C - hides a cold layer in its atmosphere. At 125 kilometres above the planet's surface, the weather is -175 °C with a good chance of carbon dioxide ice.
It is the ice that causes the brighter regions in the atmosphere. It's much colder there than anywhere on Earth, despite the fact Venus is closer to the sun.
This discovery is a bizarre twist for a planet that is famously hot and inhospitable. Even though Venus is further from the sun, it's hotter than Mercury, the result of a killer greenhouse effect. The atmospheric composition is 96.5 per cent carbon dioxide.
Håkan Svedhem, ESA's Venus Express project scientist, said in a press release that the cold layer is unique, in that Earth and Mars don't have anything like it. He added that the finding is new and more time is needed to understand its implications.
True to form, Venus is keeping it mysterious. [Journal of Geophysical Research]
Image by ESA/MPS, Katlenburg-Lindau, Germany