But is it a planet or what?

These noctilucent clouds, reflecting light from the sun after sunset, have been visible in Martian skies for the past four fall seasons. Credit: NASA / JPL-Caltech / MSSS A rover got a new view of ...

Holidaymakers have one major thing in common with scientists who are on the hunt for alien life: their plans are often thwarted by clouds. The clouds on alien worlds are such a long-standing issue – ...