(WFLA) — Stargazers in parts of Europe were stunned by an unusual sight on Monday evening: a large, glowing blue spiral in the sky ... instantly froze at the high altitude.

Clouds are a fascinating part of our sky, made up of countless ... three main groups based on their altitude: cirrus, cumulus, and stratus. Cirrus clouds are high-altitude clouds, often appearing ...

Noctilucent, or "night-shining", clouds can be seen on Mars, just as they are on Earth. Nasa's Curiosity Mars rover imaged these high-altitude clouds ... sight in the sky above the UK.