Rocks/Rocky objects/Dione

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An animation shows Dione's surface. Credit: Brandon Amaro.

Dione appears to be another ice-covered rocky object in orbit around Saturn.

Meteor sources[edit | edit source]

Cassini imaged the surface of Saturn's moon Helene as the spacecraft flew by the moon on Jan. 31, 2011. Credit: NASA / Jet Propulsion Lab / Space Science Institute.{{free media}}
Cassini images the moon Polydeuces. Credit: Cassini spacecraft.{{free media}}
Moons Helena and Polidevk (Polydeuces) are in lagrange positions with Dione. Credit: Nusha.{{free media}}

On the right, moons Helena and Polidevk (Polydeuces) are in lagrange positions with Dione.

"Cassini imaged [on the left] the surface of Saturn's moon Helene as the spacecraft flew by the moon on Jan. 31, 2011."[1]

"This small moon leads Dione by 60 degrees in the moons' shared orbit. Helene is a "Trojan" moon of Dione, named for the Trojan asteroids that orbit 60 degrees ahead of and behind Jupiter as it circles the Sun."[1]

"This view looks toward the leading hemisphere of Helene (33 kilometers, 21 miles across). North on Helene is up and rotated 2 degrees to the left."[1]

"The image was taken with the Cassini spacecraft narrow-angle camera using a combination of spectral filters sensitive to wavelengths of polarized green light centered at 617 and 568 nanometers. The view was obtained at a distance of approximately 31,000 kilometers (19,000 miles) from Helene and at a Sun-Helene-spacecraft, or phase, angle of 65 degrees. Scale in the original image was 187 meters (612 feet) per pixel. The image was contrast enhanced and magnified by a factor of 1.5 to enhance the visibility of surface features."[1]

The other image on the left shows Polydeuces which trails Dione in their orbit around Saturn.

Meteors[edit | edit source]

"Dione—discovered in 1684 by astronomer Giovanni Cassini (after whom the spacecraft was named)—orbits Saturn at roughly the same distance as our own moon orbits Earth. The tiny moon is a mere 700 miles wide and appears to be a thick, pockmarked layer of water ice surrounding a smaller rock core. As it orbits Saturn every 2.7 days, Dione is bombarded by charged particles (ions) emanating from Saturn’s very strong magnetosphere. These ions slam into the surface of Dione, displacing molecular oxygen ions into Dione’s thin atmosphere through a process called sputtering.[2]

Dione is currently in a 1:2 mean-motion orbital resonance with moon Enceladus, completing one orbit of Saturn for every two orbits completed by Enceladus, which maintains Enceladus's orbital eccentricity (0.0047), providing a source of heat for Enceladus's extensive geological activity, which shows up most dramatically in its cryovolcanic geyser-like jets.[3] The resonance also maintains a smaller eccentricity in Dione's orbit (0.0022), tidally heating it as well.[4]

Visuals[edit | edit source]

This southerly view of Dione shows enormous canyons extending from mid-latitudes on the trailing hemisphere, at right, to the moon's south polar region. Credit: NASA/JPL/Space Science Institute.

"This southerly view of Dione [on the right] shows enormous canyons extending from mid-latitudes on the trailing hemisphere, at right, to the moon's south polar region."[5]

"This view [on the right] looks toward the Saturn-facing side of Dione (1,126 kilometers, or 700 miles across) and is centered on 22 degrees south latitude, 359 degrees west longitude. North on Dione is up; the moon's south pole is seen at bottom."[5]

"The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 8, 2008. The view was obtained at a distance of approximately 211,000 kilometers (131,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 20 degrees. Image scale is 1 kilometer (0.6 mile) per pixel."[5]

Violets[edit | edit source]

Enhanced color composite of Saturn's moon Dione is based on infrared, green, ultraviolet, and clear-filter images taken by the Cassini spacecraft December 14, 2004. Credit: Matt McIrvin, Cassini/NASA.
Dione is shown here in a composite of images from Cassini. Credit: NASA, JPL, SSI, ESA.

This at right is an enhanced "color composite of Saturn's moon Dione, based on infrared, green, ultraviolet, and clear-filter images [is] taken by the Cassini spacecraft December 14, 2004."[6]

It shows "the darker, fractured terrain of the trailing hemisphere. The Padua Chasmata trace an arc on the left, interrupted near the top by central peak crater Ascanius. The Janiculum Dorsa extend along the upper right terminator. Near the lower left limb is the small crater Cassandra with its prominent ray system."[6]

At left is another image of Dione partially rotated from the one at right and showing a violet cast on the apparent higher elevation portion toward the terminator. This image is from Cassini "taken 1 August 2005 from 243,000 km away."[7]

Cyans[edit | edit source]

This image of Dione was acquired by the Cassini spacecraft narrow-angle camera. Credit: NASA/JPL.

To create this enhanced-color view of Dione on the right, ultraviolet, green and infrared images were combined into a single black and white picture that isolates and maps regional color differences. This "color map" was then superposed over a clear-filter image. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition or the sizes of grains making up the icy soil.

Yellows[edit | edit source]

This set of global, color mosaics of Saturn's moon Dione was produced from images taken by NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute.

"This set of global, color mosaics [on the right] of Saturn's moon Dione was produced from images taken by NASA's Cassini spacecraft during its first ten years exploring the Saturn system. These are the first global color maps of these moons produced from the Cassini data."[8]

"The most obvious feature on the maps is the difference in color and brightness between the two hemispheres. The darker colors on the trailing hemispheres are thought to be due to alteration by magnetospheric particles and radiation striking those surfaces. The lighter-colored leading hemisphere is coated with icy dust from Saturn's E-ring, formed from tiny particles ejected from Enceladus' south pole. These satellites are all being painted by material erupted by neighboring Enceladus."[8]

"The colors shown in these global mosaics are enhanced, or broader, relative to human vision, extending into the ultraviolet and infrared range."[8]

"Resolution on Dione in the maps is 250 meters per pixel."[8]

Rocky objects[edit | edit source]

This picture of Dione was take by Voyager 1 from a range of 162,000 kilometers on November 12, 1980. Credit: NASA/JPL.

"Many impact craters -- the record of the collision of cosmic debris -- are shown in this Voyager 1 mosaic of Saturn's moon Dione. The largest crater is less than 100 kilometers (62 miles) in diameter and shows a well-developed central peak. Bright rays represent material ejected from other impact craters. Sinuous valleys probably formed by faults break the moon's icy crust. Images in this mosaic were taken from a range of 162,000 kilometers (100,600 miles) on Nov. 12, 1980."[9]

Oxygens[edit | edit source]

Molecular "oxygen ions (O2+) in the upper-most atmosphere of Dione"[2]

"Molecular oxygen ions are then stripped from Dione’s exosphere by Saturn’s strong magnetosphere."[2]

"A sensor aboard the Cassini spacecraft called the Cassini Plasma Spectrometer (CAPS) detected the oxygen ions in Dione’s wake during a flyby of the moon in 2010."[2]

“The concentration of oxygen in Dione’s atmosphere is roughly similar to what you would find in Earth’s atmosphere at an altitude of about 300 miles. It’s not enough to sustain life, but—together with similar observations of other moons around Saturn and Jupiter—these are definitive examples of a process by which a lot of oxygen can be produced in icy celestial bodies that are bombarded by charged particles or photons from the Sun or whatever light source happens to be nearby.”[10]

Poles[edit | edit source]

This set of global, color mosaics of Saturn's moon Dione was produced from images taken by NASA's Cassini spacecraft. Credit: NASA / JPL-Caltech / Space Science Institute / Lunar and Planetary Institute.

"This set of global, color mosaics of Saturn's moon Dione was produced from images taken by NASA's Cassini spacecraft during its first ten years exploring the Saturn system. These are the first global color maps of these moons produced from the Cassini data."[11]

"The most obvious feature on the maps is the difference in color and brightness between the two hemispheres. The darker colors on the trailing hemispheres are thought to be due to alteration by magnetospheric particles and radiation striking those surfaces. The lighter-colored leading hemisphere is coated with icy dust from Saturn’s E-ring, formed from tiny particles ejected from Enceladus’ south pole. These satellites are all being painted by material erupted by neighboring Enceladus."[11]

"The colors shown in these global mosaics are enhanced, or broader, relative to human vision, extending into the ultraviolet and infrared range."[11]

"Resolution on Dione in the maps is 250 meters per pixel."[11]

Craters[edit | edit source]

This raw, unprocessed image of Dione was taken on December 12, 2011. Credit: NASA/Jet Propulsion Lab - Caltech/Space Science Institute.

"The camera was pointing toward Dione at approximately 77682 kilometers away, and the image was taken using the CL1 and CL2 filters. The image has not been validated or calibrated."[12]

The south polar impact basin named Evander, 350 km in diameter, at the bottom the of image on the right, is by far the largest crater on Dione. The deep crater to its upper left is Sabinus.

Surface faults[edit | edit source]

Fractures bisecting older craters on Dione. Credit: NASA/JPL/Space Science Institute.

"Dione's icy surface [on the right] is scarred by craters and sliced up by multiple generations of geologically-young bright fractures. Numerous fine, roughly-parallel linear grooves run across the terrain in the upper left corner."[13]

"Most of the craters seen here have bright walls and dark deposits of material on their floors. As on other Saturnian moons, rockslides on Dione (1,126 kilometers, or 700 miles across) may reveal cleaner ice, while the darker materials accumulate in areas of lower topography and lower slope (e.g. crater floors and the bases of scarps)."[13]

"The terrain seen here is centered at 15.4 degrees north latitude, 330.3 degrees west longitude, in a region called Carthage Linea. North on Dione is up and rotated 50 degrees to the left."[13]

"The image was taken in visible green light with the Cassini narrow-angle camera on Oct. 11, 2005, at a distance of approximately 19,600 kilometers (12,200 miles) from Dione. The image scale is about 230 meters (760 feet) per pixel."[13]

Rilles[edit | edit source]

Rilles are shown on Dione. Credit: NASA / JPL / Space Science Institute.

On the right is an image of rilles on Dione "taken on 2010-04-07 05:17 (UTC) and received on Earth 2010-04-07 21:54 (UTC). The camera was pointing toward Saturn, and the image was taken using the CL1 and CL2 filters."[14]

Mythology[edit | edit source]

"Zeus is the child of Cronus and Rhea, and the youngest of his siblings. In most traditions he is married to Hera, although, at the oracle of Dodona, his consort is Dione: according to the Iliad, he is the father of Aphrodite by Dione."[15]

In most traditions, Zeus is married to Hera, by whom he is usually said to have fathered Ares, Hebe, and Hephaestus.[16]

At the oracle of Dodona, his consort was said to be Dione, by whom the Iliad states that he fathered Aphrodite. There are two major conflicting stories for Aphrodite's origins: Hesiod's Theogony claims that she was born from the foam of the sea after Cronos castrated Uranus, making her Uranus's daughter but Homer's Iliad has Aphrodite as the daughter of Zeus and Dione.[17] A speaker in Plato's Symposium offers that they were separate figures: Aphrodite Ourania and Aphrodite Pandemos.[18]

Plato and Pausanias describe Aphrodite Pandemos (Venus vulgivaga or popularis) as the goddess of sensual pleasures, in opposition to Aphrodite Urania, or "the heavenly Aphrodite".[19]

Along with the Odyssey, the Iliad is among the oldest extant works of Western literature, and its written version is usually dated to around the 8th century BC (2800 b2k).[20]

See also[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 C. Porco (31 January 2011). Flying by Helene. Washington, D.C. USA: NASA's Science Mission Directorate. http://www.ciclops.org/view/6723/Flying_by_Helene?js=1. Retrieved 2016-11-06. 
  2. 2.0 2.1 2.2 2.3 James E. Rickman (2 March 2012). Oxygen detected in atmosphere of Saturn’s Moon Dione. Los Alamos, New Mexico USA: Los Alamos National Laboratory. http://www.agu.org/journals/gl/gl1203/2011GL050452/. Retrieved 2016-12-16. 
  3. Carolyn Porco; Helfenstein, P.; Thomas, P. C.; Ingersoll, A. P.; Wisdom, J.; West, R.; Neukum, G.; Denk, T. et al. (10 March 2006). "Cassini Observes the Active South Pole of Enceladus". Science 311 (5766): 1393–1401. doi:10.1126/science.1123013. PMID 16527964. 
  4. Jia-Rui Cook (May 29, 2013). "Cassini Finds Hints of Activity at Saturn Moon Dione". NASA. Retrieved October 1, 2013.
  5. 5.0 5.1 5.2 Sue Lavoie (19 March 2008). PIA09861: A Stressed Surface. Pasadena, California USA: NASA/JPL. http://photojournal.jpl.nasa.gov/catalog/PIA09861. Retrieved 2016-12-17. 
  6. 6.0 6.1 Matt McIrvin (24 March 2013). Dione (moon). San Francisco, California: Wikimedia Foundation, Inc. http://en.wikipedia.org/wiki/Dione_(moon). Retrieved 2013-04-02. 
  7. Wm. Robert Johnston (15 August 2011). A Solar System Photo Gallery Saturn and Its Satellites. johnstonsarchive. http://www.johnstonsarchive.net/astro/gallery-4.html. Retrieved 2013-04-02. 
  8. 8.0 8.1 8.2 8.3 Paul Schenk (4 November 2014). Color Maps of Dione - 2014. Pasadena, California USA: NASA/JPL. http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA18434. Retrieved 2016-12-17. 
  9. Sue Lavoie (12 November 1980). PIA00028: Dione Mosaic. Pasadena, California USA: NASA/JPL. http://photojournal.jpl.nasa.gov/catalog/PIA00028. Retrieved 2016-12-18. 
  10. Robert Tokar and Michelle Thomsen (2 March 2012). Oxygen detected in atmosphere of Saturn’s Moon Dione. Los Alamos, New Mexico USA: Los Alamos National Laboratory. http://www.agu.org/journals/gl/gl1203/2011GL050452/. Retrieved 2016-12-16. 
  11. 11.0 11.1 11.2 11.3 Paul Schenk (4 November 2014). Color maps of Dione - November 2014. Pasadena, California USA: NASA/JPL. http://www.ciclops.org/view/7960/Color-maps-of-Dione---November-2014?js=1. Retrieved 2016-12-17. 
  12. C. Porco (12 December 2011). Dione 'Rev 158' Raw Preview #1. ciclops. http://www.ciclops.org/view.php?id=6992&js=1. Retrieved 2016-12-17. 
  13. 13.0 13.1 13.2 13.3 Sue Lavoie (24 November 2005). PIA07638: At Carthage Linea. Pasadena, California USA: NASA/JPL. http://photojournal.jpl.nasa.gov/catalog/?IDNumber=PIA07638. Retrieved 2016-12-17. 
  14. Bill Dunford, Enrico Piazza and Jay R. Thompson (7 April 2010). Image of Saturn. Pasadena, California USA: NASA/JPL. https://saturn.jpl.nasa.gov/raw_images/243311/. Retrieved 2016-12-18. 
  15. Atcovi (26 November 2013). "Classical Mythology/Zeus". San Francisco, California USA: Wikimedia Foundation, Inc. Retrieved 7 October 2019.
  16. Hamilton, Edith (1942). Mythology (1998 ed.). New York: Back Bay Books. p. 467. ISBN 978-0-316-34114-1. https://archive.org/details/mythologytimeles00hami_1. 
  17. Homer, Iliad (Il)., Book V.
  18. Plato, Symp., 180e.
  19. Plato, Symposium 180d; Lucret. iv. 1067.
  20. Pierre Vidal-Naquet. Le monde d'Homère (The World of Homer), Perrin (2000), p. 19

External links[edit | edit source]