Cassini bids farewell to Hyperion, heads to Dione

Chuck Bednar for redOrbit.com – @BednarChuck

After getting one last up-close look at Saturn’s moon Hyperion on Sunday, NASA’s Cassini spacecraft is now en route to Dione, a small, icy moon that orbits the planet at roughly the same distance that the moon orbits the Earth, the US space agency has announced.

That flyby is scheduled for June 16, when Cassini will pass 321 miles (516 kilometers) above the surface of the moon. Hyperion is constantly bombarded by fine ice powder originating from Saturn’s E-ring and has a heavily cratered terrain with up to 62 miles (100 kilometers) across.

Interestingly enough, Dione is most heavily cratered on its trailing hemisphere – something that NASA explained should not be the case. Typically, a moon’s leading hemisphere should be more heavily cratered than the trailing one, but experts hypothesize that a relatively recent impact may have caused the moon spin around 180 degrees to its current position.

One last look at Hyperion before moving on

Before setting off to explore this unusual moon, however, Cassini made a final flyby of Saturn’s so-called spongy moon, Hyperion, coming to within 21,000 miles (34,000 km) of its surface and managing to collect some stunning new images, according to Discovery News.

One picture, the website explained, is a color composite created from images acquired in optical wavelengths using the spacecraft’s red, green, and blue filters. The contrast and color saturation were then enhanced to show what Hyperion – the largest of Saturn’s irregularly-shaped moons – would have looked like to an astronaut travelling on board Cassini.

According to NASA, Hyperion has a deeply-cratered surface, and many of those craters are deep and lack significant rays of ejecta, giving the moon’s surface a “punched-in look” similar to a sponge or a wasp’s nest. In addition, many of its crater walls are bright, suggesting the presence of ice water, and it has an eccentric orbit that takes it around Saturn every 21 days.

Cassini will not return to Hyperion during its mission. After leaving Dione, it will make a pair of close flybys of Enceladus in October, coming to within 30 miles (48 km) during the final pass. It will then leave Saturn’s equatorial plane to begin the final year of its mission, as the probe is set to spend 2016 repeatedly diving in-between the planet and its rings.

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