Nacreous clouds form over polar regions in our lower stratosphere between 68,500 and 100,000 feet (13 and 19 miles or 20 and 30 kilometers) according to the UK Met Office.

Watching clouds is a solitary activity for me, even when I'm surrounded by people. If you have a drink or a meal with me in an outdoor café, my eyes will periodically turn to the sky. Every once ...

The clouds photographed by Curiosity are at an altitude of 37 to 50 miles above the planet's surface. Other images show the clouds as white plumes falling through the atmosphere, before ...