retrograde
BIG BRIGHT CLOUD ON #MARS: If you look at Mars through a telescope this week, you might be surprised by what you see--a bright blue cloud of ice. Michael Karrer photographed it on Nov. 7th from his backyard in Austria:

"Mars is no longer dusty and the north pole has dense cloud cover - very impressive despite the planet's modest diameter of 15.8 arcseconds," he says.

Karrer photographed the North Polar Hood, a giant cloud of water ice that forms over the Martian north pole during winter. Why blue? That's the color of sunlight scattered from very tiny crystals of ice (smaller than the wavelength of light itself) floating in the cloud.

"It was easy to see through my 14-inch Celestron telescope," adds Kerrer. "And it's about to get even easier."

Mars is approaching Earth for a close encounter on Dec. 1, 2022. Between now and then, Mars will double in brightness to magnitude -1.9 (brighter than Sirius) and increase in size to 17.2 arcseconds. Look for the Red Planet and its blue hood rising in the east after sunset in the constellation Taurus