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NASA celebrates 10 years of Cassini at Saturn with top-ten list of amazing discoveries


Monday, June 30, 2014, 7:39 - Ten years ago today, on June 30, 2004, NASA's Cassini arrived at Saturn, dropping into the ringed gas giant's gravity well and beginning the first of its four-year missions to investigate the planet, its extensive ring system and its multitude of mysterious moons.

When the Cassini-Huygens mission arrived at its destination back in 2004, the scientists and engineers involved in the mission were understandably quite happy, as the video below shows:

After all, while the team had a few milestones on the spacecraft's trip - flybys of Venus, Earth and Jupiter, and testing out Einstein's Theory of Relativity - the day they had all been awaiting for nearly 7 years had finally arrived. It was well-worth the wait, too, as Cassini has returned some incredible discoveries and spectacular images over the past 10 years. Here's a personal "Top Ten" from Cassini's first 10 years:

1. Titan's surface is revealed, giving us a glimpse of what Earth was like in the distant past.


(Credit: Originals from ESA/NASA/JPL/University of Arizona(right) and NASA/JPL-Caltech/University of Arizona/University of Idaho(left), combined by S.Sutherland)

Dropping its Huygens probe into the hazy methane atmosphere of Titan, and then following that up with radar images over the past nine-and-a-half years, NASA and the European Space Agency captured the first images of the moon's surface (left) and produced extensive maps of the features on the surface, such as the various hydrocarbon lakes (right). These views revealed that Titan is very much like Earth way, before life developed on our planet, nearly 4 billion years ago.

2. Cassini catches icy moon Enceladus blasting out water vapour plumes, hinting at subsurface ocean


(Credit: Originals by NASA/JPL/Space Science Institute, combined by S.Sutherland)

This image, taken by Cassini on Nov. 27, 2005, shows plumes of water vapour streaming off the south polar region of Enceladus, one of Saturn's innermost moons. Nearly two years later, researchers completed a study on these plumes, using enhanced images like in the colour overlay to identify the individual fountains. More recently, flybys of Cassini detected a region under these plumes where the pull of gravity is lower than the surrounding area, suggesting that there is an extensive ocean of liquid water under the icy surface.

3. Cassini sees tall vertical structures in Saturn's rings


(Credit: NASA/JPL/SSI)

In late July of 2009, just weeks before Saturn reached its equinox - when the planet's northern and southern hemispheres would receive equal light from the Sun - Cassini snapped this image of the outer edge the B ring and the Cassini division. With the light from the Sun hitting the rings nearly edge-on, towering spires, some reaching to 2.5 kilometres above the 'surface' of the rings, cast long shadows across the ice.

4. Saturn's northern polar hurricane imaged in stunning detail


Credit: NASA/JPL-Caltech/SSI/Hampton University

This animated image shows off a false-colour view of 'the hexagon' - a persistent feature that surrounds Saturn's north pole. For a sense of scale, you could fit two Earths side-by-side across the entire hexagon, and the swirling hurricane at its centre (shown in the deepest pinks and purples) has an eye roughly 50 times larger than the eye of your typical Earth hurricane. A beautiful, natural colour still image of the hexagon, which has been named Spring at the North Pole, can be seen on NASA's website (click here). It took five years before Cassini got its first hints of the existence of this feature, since Saturn's northern hemisphere was in winter until 2009, so the north pole was hidden in shadow. These images were captured as the spacecraft flew directly over the north pole, and the feature will remain visible until sometime in 2025, when the north pole slips back into shadow. 

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