North Pole of Saturn's Moon Enceladus Seen In Fresh Detail

Like NASA's New Horizons spacecraft, which is gradually transmitting spectacular images of its unprecedented July 14 flyby of Pluto back to Earth, the even longer running Cassini mission at Saturn is breaking new ground in the outer solar system with stunning new close-up photos of Enceladus -- a geothermally active snowball of a moon recently determine to harbor a global ice covered ocean.

Images snapped as Cassini passed within 1,142 miles of Enceladus' north pole on Wednesday reveal a heavily cratered terrain with a spidery network of very thin cracks that slice through the craters.

"These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well," noted Paul Helfenstein, of Cornell University, a member of the Cassini imaging team, as the first images from this week's close pass arrived at Earth on Thursday.

Cassini, a joint mission of NASA, the European Space Agency and the Italian Space Agency, was launched in 1997. The spacecraft  maneuvered into orbit around Saturn in 2004 and dropped a small lander onto the surface of the dynamic moon Titan. Cassini's successful four year prime mission has been twice extended as it explores Saturn's ring system and many moons. Mission operations are now expected to continue through September 2017.

And there's more to come from Enceladus, which like Mars and Jupiter's moon Europa hint at potentially habitable environments.

In 2005, Cassini spotted ice plumes rising from the south pole of Enceladus. In 2014, the plumes were linked to what was believed at the time to be a regional sea below the icy surface.

Closer scrutiny shows the plumes rise in curtain like sprays from long cracks in the moon's surface. Follow on analysis suggests Enceladus has a rocky core with a global ocean beneath an ice layer rather than a smaller sea.

Scientists suggest tidal forces exerted by giant Saturn and reactions between the water and rocky ocean floor of Enceladus furnish the hydrothermal energy behind the curtain like sprays.

Cassini is to dip within 30 miles of Enceladus' south pole on Oct. 28. As it passes through the icy spray, instruments on the spacecraft will attempt to identify the ocean chemistry and the extent of the hydrothermal energy in the subsurface ocean to further address the potential for habitability.

The spacecraft's final close Enceladus flyby is to take place on Dec. 19 from an altitude of 3,106 miles. Cassini will attempt to measure the amount of heat rising from the moon's interior.