On June 16th NASA’s Cassini spacecraft came super close to Saturn’s moon Dione. It was only 321 miles away from the moon’s surface.
The region was first observed by NASA’s Voyager mission 35 years ago and the possibility arose that the bright wispy streaks could be extruded onto the surface by ice volcanoes.
Sharp visuals from Cassini’s close contact revealed the bright streaks to be a network of braided canyons with bright walls, called linea.
The space craft will also try and detect any fine particles being emitted from the moon, which includes low-level geological activity.
At 1122 km (697 mi) in diameter, Dione is the 15th largest moon in the Solar System, and is more massive than all known moons smaller than itself combined. It is composed primarily of water ice, and is the third densest of Saturn’s moons.
Within a few days of the encounter visuals will begin arriving. In Cassini’s long mission this is the fourth encounter with Dione. Targeted encounters require a propulsion maneuver to precisely steer the spacecraft toward a desired path above a moon.
In December 2011 was Cassini’s closest – ever flyby of Dione,
On August 17th the spacecraft will once more flyby Dione, within 295 miles of the surface.
The spacecraft is expected to depart Saturn’s equatorial plane in late 2015, where moon flyby’s occur more frequently, and will begin a year-long setup of the mission’s final year.
Cassini’s final mission is to dive through the space between Saturn and its rings.
Cassini is a collective project of NASA , ESA and the Italian Space Agency.