Talk about a parting shot! NASA's Cassini spacecraft ends its mission in late 2017, but not before it took one more look at Saturn's moon Dione -- and sent back some stunning close-ups.
Dione's pockmarked surface looks magnificent as it hovers above the planet's signature rings in an image taken Aug. 17. During the flyby – Cassini's fifth of Dione – the spacecraft came within 295 miles of the surface.
"They are the last we will see of this far-off world for a very long time to come," Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo., said of the images. "Right down to the last, Cassini has faithfully delivered another extraordinary set of riches. How lucky we have been."
As far as closeups go, these images are pretty flattering – and useful. That's because the researchers were able to take advantage of extra sunlight reflecting off the gas-giant planet to help illuminate additional features hidden in the cratered moon's shadows.
The images were actually just icing on the flyby's cake – this fifth and final close encounter of Dione was primarily to study the moon's gravitational field, not to take pictures. This meant there wasn't much guarantee that the spacecraft would be properly positioned to take images, because Cassini's camera wasn't controlling the way the spacecraft pointed.
Together with data from the spacecraft's magnetosphere and plasma-sensing instruments, the gravity data will help planetary scientists better understand the icy moon's interior.
After this, Cassini won't be making many more close flybys. It will visit the water-rich moon Enceladus three more times this year, passing as close as 30 miles above the surface during one of them, and it will dive through the icy plume spraying out of the surface, to learn more about the frigid little world's interior. It will also perform a few farther-out flybys of Saturn's moons (within about 30,000 miles), and will check out the smaller, more "misshapen" moons, including Daphnis and Telesto.
Near the end of its mission, Cassini will perform an acrobatic finale, executing a series of dives through the gap between the planet and its iconic rings.