Seasons are changing on Earth. Ditto on Mars. While we are moving to spring and summer, winter has just begun at the Martian north pole, and icy-blue clouds are gathering there. Jefferson Teng photographed them last week from Bandar Lampung, Indonesia.
“Good sighting allowed me to get this Mars image through my 11-inch telescope,” says Teng. “The bluish north hemisphere clouds were simply breathtaking.”
Astronomers call this the “North Polar Hood.” It is made of ice crystals of H2O and CO2, floating high above the Martian arctic circle. These tiny crystals give the hood its blue colour by preferentially scattering short (blue) wavelengths of sunlight.
The giant blue cloud will expand and intensify in the weeks ahead as Mars moves deeper into northern winter. Perfect timing for observers on Earth: we’re having a close encounter with Mars on 6 October, and the North Polar Hood will be very easy to see.