Cassini’s farewell tour officially got underway on Monday, as the NASA spacecraft made its final close flyby of Saturn’s icy moon Dione and conducted a gravity experiment during closest approach to the satellite, officials from the US space agency have confirmed.
The probe made its closest approach to Dione’s surface at 2:33pm EDT (11:33am PDT), coming within 295 miles (474 km) of the moon’s surface. During the flyby, it collected data about the internal structure of the satellite and the rigidity of its outer shell, as well as a set of observations from the well-lit, anti-Saturn side using its camera and spectrometer instruments.
In a statement, mission controllers said that they expected the first new images to start arriving on Earth within a few days following Cassini’s final encounter with the moon. During the flyby, the spacecraft’s instruments were expected to get a high-resolution look at Dione’s north pole, a feature that it had not previously been able to get a good look at.
In addition, the probe’s Composite Infrared Spectrometer (CIRS) was set to map areas on the icy moon that had unusual thermal anomalies, or regions that are especially good at trapping heat. In addition, Cassini’s Cosmic Dust Analyzer was set to continue its search for dust particles emitted by the moon during its fifth targeted encounter with Dione.
Taking one final look at ‘an enigma’
“Dione has been an enigma,” said Bonnie Buratti, a Cassini science team member at the NASA Jet Propulsion Laboratory (JPL) in California. She explained that it has been “giving hints of active geologic processes, including a transient atmosphere and evidence of ice volcanoes. But we’ve never found the smoking gun. The fifth flyby of Dione will be our last chance.”
“This will be our last chance to see Dione up close for many years to come,” added Cassini deputy project scientist Scott Edgington. “Cassini has provided insights into this icy moon’s mysteries, along with a rich data set and a host of new questions for scientists to ponder.”
Cassini, which has been orbiting Saturn since 2004, is currently completing a series of final close moon flybys, after which time it will leave Saturn’s equatorial plane to begin a year-long setup of its final year of operation. During that last phase of the mission, the spacecraft will be repeatedly diving through the space between Saturn and its rings, according to the US space agency.
Cassini’s closest-ever flyby of Dione was in December 2011, when it came to within 60 miles (100 km) of the moon’s surface. It has revealed that the bright, wispy terrain on the satellite is a system of braided canyons with bright walls, and project scientists are hopeful that they will be able to find out if it has geologic activity similar to that found on Enceladus.
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Feature Image: While not bursting with activity like its system sister Enceladus, the surface of Dione is definitely not boring. Some parts of the surface are covered by linear features, called chasmata, which provide dramatic contrast to the round impact craters that typically cover moons. (Credit: NASA/JPL-Caltech/Space Science Institute)
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