NASA's Cassini makes final approach to fly-by Saturn's moon Dione on June 16

NASA's Cassini spacecraft will cruise very close to of Saturn's moon Dione on June 16.

Spacecraft would be coming within 321 miles of the moon's surface. It will fly past Dione one more time, on Aug. 17, swooping within 295 miles of the surface.

During the flyby, Cassini's cameras and spectrometers will observe terrain that includes "Eurotas Chasmata," a region first observed 35 years ago by NASA's Voyager mission as bright, wispy streaks.

After the Voyager encounter, scientists considered the possibility that the streaks were bright material extruded onto the surface by geologic activity, such as ice volcanoes.

Cassini's close flybys and sharp vision later revealed the bright streaks to be an intricate network of braided canyons with bright walls, called lineae.

Cassini will also try to detect and determine the composition of any fine particles being emitted from Dione, which could indicate low-level geologic activity.