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Cassini views Helorus in half-light

22 March 2016 Astronomy Now

In this image from NASA’s Cassini spacecraft we see a crater duo on Saturn’s 698-mile-wide moon Dione. The upper of the pair, named Italus, is overprinted on a grouping of ancient troughs called Petelia Fossae. The lower crater, Caieta, sits atop a feature named Helorus Fossa. Fossae on Dione are believed to be tectonic features.

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Saturn’s rings: less than meets the eye?

3 February 2016 Astronomy Now

You might think that, in the rings of Saturn, more opaque areas contain a greater concentration of material than places where the rings seem more transparent. But this intuition does not always apply, according to a recent study of the rings using data from NASA’s Cassini mission. The research also suggests that the planet’s brightest B ring could be a few hundred million years old instead of a few billion.

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Saturn’s moons Janus and Tethys

19 January 2016 Astronomy Now

Janus and Tethys demonstrate the main difference between small moons and large ones; it’s all about their shape. Moons like Tethys are large enough that their own gravity is sufficient to overcome the material strength of the substances they are made of and mould them into spherical shapes, but small moons like Janus are not massive enough for their gravity to form them into a sphere.

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Cassini completes final close flyby of Saturn’s moon Enceladus

22 December 2015 Astronomy Now

NASA’s Cassini spacecraft has begun transmitting data and images from the mission’s 22nd and final close flyby of Saturn’s active moon Enceladus on Saturday, 19 December. Cassini has made so many breathtaking discoveries about this icy moon, its geologic activity and global ocean that lies beneath its icy crust, yet so much more remains to be done to determine if this tiny ocean world could harbour life.

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Enceladus: water world

30 November 2015 Astronomy Now

This view of Saturn’s moon Enceladus above the planet’s ring plane was captured by the narrow-angle camera of NASA’s Cassini spacecraft at a distance of approximately 630,000 miles (1 million kilometres) from the tiny water world. Enceladus is subject to forces that heat a global ocean of liquid water under its icy surface, resulting in its famous south polar water jets which are just visible below the moon’s dark, southern limb.

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Cassini ready to dive deep into Saturn moon’s erupting water plume

27 October 2015 Astronomy Now

On Wednesday, 28 October 2015, NASA’s Cassini spacecraft will take the deepest dive ever through the plume of ice, water vapour and organic molecules spraying from the south polar region of Saturn’s moon Enceladus. Scientists hope this close flyby will shed light on what’s happening beneath the moon’s icy surface. With a global ocean and likely hydrothermal activity, could Enceladus have the ingredients needed to support simple forms of life?

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Cassini finds global ocean under icy crust of Saturn’s moon Enceladus

15 September 2015 Astronomy Now

A global ocean lies beneath the icy crust of Saturn’s geologically active moon Enceladus, according to new research using data from NASA’s Cassini mission. Researchers found the magnitude of the moon’s very slight wobble, as it orbits Saturn, can only be accounted for if its outer ice shell is not frozen solid to its interior, meaning a global ocean must be present.

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One of Saturn’s rings is not like the others

5 September 2015 Astronomy Now

NASA’s Cassini mission scientists were watching closely when the Sun set on Saturn’s rings in August 2009. It was the equinox — one of two times in the Saturnian year when the Sun illuminates the planet’s enormous ring system edge-on — providing an extraordinary opportunity for the spacecraft to observe short-lived changes that reveal details about the nature of the rings.

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Cassini’s final breathtaking close views of Saturn’s moon Dione

21 August 2015 Astronomy Now

A pockmarked, icy landscape looms beneath NASA’s Cassini spacecraft in new images of Saturn’s moon Dione taken during the mission’s last close approach to the small, frozen world. Two of the new images show the surface of Dione at the best resolution ever. Cassini passed 295 miles (474 kilometres) above Dione’s surface at 7:33pm BST on 17 August 2015.

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Chasms on Dione

18 August 2015 Astronomy Now

While not bursting with activity like its sister moon Enceladus, the surface of Saturn’s moon Dione is definitely not boring. Some parts of the surface are covered by linear features, called chasmata — bright icy cliffs among myriad fractures — which provide dramatic contrast to the round impact craters that typically cover moons.