Cassini ’s epic missionary station to Saturn is coming to a last with a spectacular finale of daring flybys and swooping encounters . The beginning of the conclusion happened today with the last targeted flyby of Dione , the polar moon of hulk cliffs and dizzying canyons .
Dione against the backdrop of Saturn in blue , green , and infrared light on October 11 , 2005 from 39,000 kilometre ( 24,200 miles ) off for 2 kilometer ( 1 mile ) per pixel resolution . Image credit : NASA / JPL / Space Science Institute
Cassini came to within just 474 kilometer ( 295 miles ) of Dione at 11:33 am on Monday , August 17 , 2015 . The images are presently beingsent back to Earth via the Deep Space web — you could mark out the raw images as they ’re released here . This was the final targeted flyby of the ice moon ; from here on out the space vehicle will be making a final tour of the Saturn system with no clock time for roundabout way before going tintinnabulation - diving in 2016 and barge in into the gaseous state giant star in September 2017 .
What have we teach about Saturn ’s fourth largest moon during the Cassini mission ?
Dione as seen on June 16 , 2015 from 77,000 kilometer ( 48,000 miles ) away from the gaseous state giant , cut across Saturn ’s rings . Image credit entry : NASA
Dione was discovered in 1684 by Giovanni Cassini , and was named for the Greek titan Dione , girl ofTethysand Oceanus , and mother of Aphrodite .
Dione [ upper ] and Tethys [ gloomy ] on April 4 , 2015 . Image credit : NASA
The first flyby of the little moon wasin November 1980 as part of Voyager 1 ’s sail through the solar arrangement . The investigation passed within 161,520 kilometers ( 100,364 mile ) at cheeseparing approach , bring about figure of speech of Eurotas Chasmata at a resolution of roughly a kilometer ( 0.6 sea mile ) per pel .
Map of Dione build from Voyager flyby data . Image recognition : NASA / USGS
Dione orb Saturn at 377,400 kilometers ( 209,651 mile ) , roughly the same aloofness as the lunation around the world . It has a mass of 1.10 x 1021 kilogram , or roughly the same as all the water in Earth ’s ocean . With a diameter of 1,118 kilometers ( 695 mile ) , it is the fourthly largest of Saturn ’s moons . Dione has a density of about 1.43 grams per cubic centimetre . That ’s high enough to propose that Dione has a thick rock’n’roll core muffled in a thickheaded mantle of ice .
Raw icon of Dione with Saturn in the background seen on the August 17 , 2015 flyby . mental image recognition : NASA / JPL - Caltech / Space Science Institute
The first flyby of Dione since Voyager was almost a decade ago on October 11 , 2005 when Cassini swooped 1,000 km ( 621 miles ) past the moon , catch closer with each subsequent flyby until the close plan of attack from just 99 kilometers ( 62 miles ) away on December 12 , 2011 . Since then , it made another quick pass earlier this summertime before today ’s final flyby . In all those flybys , Cassini has pieced together a full map of the little lunar month . The moon map is at an array of resolutions : this final flyby demand a targeted high - answer peek at Dione ’s north pole to only a few meters per a pixel .
Map of Dione ; places are named for Virgil ’s Aeneid . Image citation : NASA / USGS
The Cassini space vehicle convey gravity measurements during the flyby , allowing for investigating the moon ’s interior structure . Only a few of Saturn ’s 62 know moons have been poke in this manner . Cassini also keep its Composite Infrared Spectrometer on and pointed at the small lunar month , reckon for any thermal anomalies to identify places on the icy lunar month that are unusually good at trapping heat . As always , the Cosmic Dust Analyzer is continuously monitor for any dust corpuscle emit by the moonlight .
Saturn and the main moons of its 62 known satellite . Image mention : NASA
Dione is tidally locked to Saturn so the same side always faces the massive natural gas behemoth . It has exert its own lock on two belittled Moon : Helene and Polydeuces give ear out 60 ° forward and behind the moon in the L4 and L5 Lagrange points . The moon is also in resonance with two other moons . Dione , Mimas , and Enceladus perform a complex dance where they speed up as they approach and slow down as they take up off ; the upshot preserve Enceladus in an orbit precisely half the period of Dione ’s orbit .
Map of Dione using infrared , green , and ultraviolet wavelength with a resolution vagabond from 200 metre to 1.4 klick per pel . prototype credit : NASA / Paul Schenk / LPI
Dione ’s color is decidedly lopsided : the run cerebral hemisphere of the tidally - locked Sun Myung Moon is constantly coat in fresh ice from the E - ring while the get behind hemisphere is more heavily cratered . This is a bit rummy as normally , the conduce cerebral hemisphere should be intemperately cratered , so the current theory is that a late , massive impact spin the moonshine around . Any of the many 35 - kilometre ( 22 - mile ) diameter craters could be evidence of a sufficiently emphatic to spin the moon around , although it ’d still be foreign to be a perfect 180 ° reversal .
Although Dione does not have indisputable evidence of recent geological activity , it testify tracing of an active past infaultsand crustal rooftree .
Janiculum Dorsa , an 800 kilometer ( 500 international nautical mile ) foresightful sinuate plenty / reach vary in elevation from 1 to 2 kilometers ( 0.6 to 1.2 miels ) , a crustal crook evoke Dione ’s frozen crust was fond in the recent past . Image credit : NASA / JPL - Caltech / SSI / Brown
Younger short - coloured fractures cross the trailing hemisphere . The wispy lines are ice canyons with walls up to hundreds of meters tall , expose as grim fabric cast off off the walls to expose bright water chicken feed . The canyon are possibly form by subsidence cracks ; they might be alater stageof the same unconscious process that createthe Panthera tigris stripes on Enceladus .
Previous flybys have almost but not quite provided grounds for if Dione get together the ranks of geologically alive small frosty macrocosm . Cassini science team appendage Bonnie Buratti explains :
Dione has been an enigma , giving hint of active geologic process , including a transient ambiance and evidence of ice volcano . But we ’ve never found the smoking gun . The fifth flyby of Dione will be our last chance .
Raw simulacrum of Dione consider during the terminal aim flyby on August 17 , 2015 . Image credit : NASA / JPL - Caltech / Space Science Institute
After completing the Dione flyby , Cassini will continue its concluding hitch of Saturn ’s moons . It will swing out of the equatorial plane in late 2015 , setting up next year for its grand finale by edging closer to the rings . The spacecraft will dive between the gas whale and its rings in late 2016 before crash into Saturn ’s ambiance as the wondrous closing curtain to the missionary post in 2017 .
Cassini ’s domain from insertion around Saturn on June 30 , 2004 through its planned end - of - military mission on September 15 , 2017 . The orbital cavity of Titan is marked in red , and six other moons are mark in white . Image credit : NASA / JPL - Caltech
you’re able to watch a compilation of images of Dione taken by Cassini in this farewell video to the icy moonshine :
The images from today ’s flyby will be sent home over the next few day . you may chink out the raw paradigm here .
[ NASA ]
Saturn
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