Summer on Saturn and an icy pole

Sometimes all you need for a great photo is an interesting subject. Here we present two such examples.

Above is a striking image of Saturn in its northern hemisphere summer, with its finely etched concentric ring structure nicely resolved and two of its icy moons just visible: Mimas at right, and Enceladus at bottom.

NASA’s Hubble Space Telescope captured a slight reddish haze over the planet’s north in this colour composite, while the south pole has a blue hue.

The red may be due to heating from increased sunlight, which could alter the atmospheric circulation or perhaps remove ices from aerosols in the atmosphere. Or the increased sunlight in the summer may change the amount of photochemical haze produced.

“It’s amazing that even over a few years, we’re seeing seasonal changes on Saturn,” says lead investigator Amy Simon, from of NASA’s Goddard Space Flight Centre.

Below are the first pictures of the northern frontier of Jupiter’s moon Ganymede – the ninth-largest object in the Solar System (beating Mercury), and the only moon with its own magnetic field.

The infrared images were taken by the Jovian Infrared Auroral Mapper (JIRAM) on board NASA’s Juno spacecraft when it was about 100,000 kilometres from the moon’s surface on its way to making a flyby of Jupiter. The mission crew realised the north pole would be fully in view, and directed their instruments accordingly.

Ganymede is primarily water ice. As it has no atmosphere to impede their progress, the surface at its poles is constantly being bombarded by plasma from Jupiter’s gigantic magnetosphere – which has a dramatic effect on that ice.

Frozen water molecules detected at both poles have no appreciable order to their arrangement, and the amorphous ice has a different infrared signature than the crystalline ice found at the equator.