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Tiger stripes (Enceladus)

January 01, 1970

For other uses, see Tiger stripes.

The tiger stripes of Enceladus consist of four sub-parallel, linear depressions in the south polar region of the Saturnian moon.[1][2] First observed on May 20, 2005, by the Cassini spacecraft's Imaging Science Sub-system (ISS) camera (though seen obliquely during an early flyby), the features are most notable in lower resolution images by their brightness contrast from the surrounding terrain.[3] Higher resolution observations were obtained by Cassini's various instruments during a close flyby of Enceladus on July 14, 2005. These observations revealed the tiger stripes to be low ridges with a central fracture.[2] Observations from the Composite Infrared Spectrometer (CIRS) instrument showed the tiger stripes to have elevated surface temperatures, indicative of present-day cryovolcanism on Enceladus centered on the tiger stripes.[4]

Cassini view of Enceladus's south pole. The tiger stripes, from lower left to upper right, are the Damascus, Baghdad, Cairo, Alexandria and Camphor sulci.

Names edit

The name tiger stripes is an unofficial term given to these four features based on their distinctive albedo. Enceladean sulci (subparallel furrows and ridges), like Samarkand Sulci and Harran Sulci, have been named after cities or countries referred to in The Arabian Nights. Accordingly, in November 2006, the tiger stripes were assigned the official names Alexandria Sulcus, Cairo Sulcus, Baghdad Sulcus and Damascus Sulcus (Camphor Sulcus is a smaller feature that branches off Alexandria Sulcus).[5] Baghdad and Damascus sulci are the most active, while Alexandria Sulcus is the least active.

Appearance and geology edit

 
Composite map of the southern hemisphere of Enceladus (2007)

Images from the ISS camera onboard Cassini revealed the 4 tiger stripes to be a series of sub-parallel, linear depressions flanked on each side by low ridges.[2] On average, each tiger stripe depression is 130 kilometers long, 2 kilometers wide, and 500 meters deep. The flanking ridges are, on average, 100 meters tall and 2–4 kilometers wide. Given their appearance and their geologic setting within a heavily tectonically deformed region, the tiger stripes are likely to be tectonic fractures.[2] However, their correlation with internal heat and a large, water vapor plume suggests that tiger stripes might be the result of fissures in Enceladus' lithosphere. The stripes are spaced approximately 35 kilometers apart. The ends of each tiger stripe differ in appearance between the anti-Saturnian and sub-Saturnian hemisphere. On the anti-Saturnian hemisphere, the stripes terminate in hook-shaped bends, while the sub-Saturnian tips bifurcate dendritically.[2]

Virtually no impact craters have been found on or near the tiger stripes, suggesting a very young surface age. Surface age estimates based on crater counting yielded an age of 4–100 million years assuming a lunar-like cratering flux and 0.5-1 million years assuming a constant cratering flux.[2]

Composition edit

Another aspect that distinguishes the tiger stripes from the rest of the surface of Enceladus are their unusual composition. Nearly the entire surface of Enceladus is covered in a blanket of fine-grained water ice. The ridges that surround the tiger stripes are often covered in coarse-grained, crystalline water ice.[2][6] This material appears dark in the Cassini camera's IR3 filter (central wavelength 930 nanometers), giving the tiger stripes a dark appearance in clear-filter images and a blue-green appearance in false-color, near-ultraviolet, green, near-infrared images. The Visual and Infrared Mapping Spectrometer (VIMS) instrument also detected trapped carbon dioxide ice and simple organics within the tiger stripes.[6] Simple organic material has not been detected anywhere else on the surface of Enceladus.

The detection of crystalline water ice along the tiger stripes also provides an age constraint. Crystalline water ice gradually loses its crystal structure after being cooled and subjected to the Saturnian magnetospheric environment. Such a transformation into finer-grained, amorphous water ice is thought to take a few decades to a thousand years.[7]

Cryovolcanism edit

See also: Cryovolcano
 
Enceladus - South Pole - Geyser basin (August 10, 2014).[8]
 
Enceladus - South Pole - Geysers spray water from many locations along the "tiger stripes".

Observations by Cassini during the July 14, 2005 flyby revealed a cryovolcanically active region on Enceladus centered on the tiger stripe region. The CIRS instrument revealed the entire tiger stripe region (south of 70° South latitude) to be warmer than expected if the region were heated solely from sunlight.[4] Higher resolution observations revealed that the hottest material near Enceladus' south pole is located within the tiger stripe fractures. Color temperatures between 113 and 157 kelvins have been obtained from the CIRS data, significantly warmer than the expected 68 kelvins for this region of Enceladus.

Data from the ISS, Ion and Neutral Mass Spectrometer (INMS), Cosmic Dust Analyser (CDA) and CIRS instruments show that a plume of water vapor and ice, methane, carbon dioxide, and nitrogen emanates from a series of jets located within the tiger stripes.[9][10] The amount of material within the plume suggests that the plume is generated from a near-surface body of liquid water.[2] Over 100 geysers have been identified on Enceladus.[8]

Alternatively, Kieffer et al. (2006) suggest that Enceladus' geysers originate from clathrate hydrates, where carbon dioxide, methane, and nitrogen are released when exposed to the vacuum of space by the fractures.[11]

Enceladus - Cryovolcanism
  •  
    One possible scheme for Enceladus's cryovolcanism
  •  
    Possible origins of methane found in plumes through its subsurface ocean
  •  
    Chemical composition of the plumes of Enceladus

Relation to E-Ring of Saturn edit

Plumes from the moon Enceladus, which seems similar in chemical makeup to comets,[12] have been shown to be the source of the material in the E Ring.[13] The E Ring is the widest and outermost ring of Saturn (except for the tenuous Phoebe ring). It is an extremely wide but diffuse disk of microscopic icy or dusty material. The E ring is distributed between the orbits of Mimas and Titan.[14]

Numerous mathematical models show that this ring is unstable, with a lifespan between 10,000 and 1,000,000 years, therefore, particles composing it must be constantly replenished.[15] Enceladus is orbiting inside this ring, in a place where it is narrowest but present in its highest density, raising suspicion since the 1980s that Enceladus is the main source of particles for the E ring.[16][17][18][19] This hypothesis was confirmed by Cassini's first two close flybys in 2005.[20][21]

 
 
View of Enceladus's orbit from the side, showing Enceladus in relation to Saturn's E ring
  •  
    Enceladus orbiting within Saturn's E ring
  •  
    Enceladus geyser tendrils - comparison of images ("a";"c") with computer simulations
  •  
    Enceladus south polar region - locations of most active tendril-producing geysers
 
Eruptions on Enceladus may seem to be "discrete" jets, but may be "curtain" eruptions instead
(video animation)

References edit

  1. ^ Drake, Nadia (9 December 2019). "How an Icy Moon of Saturn Got Its Stripes - Scientists have developed an explanation for one of the most striking features of Enceladus, an ocean world that has the right ingredients for life". The New York Times. Retrieved 11 December 2019.
  2. ^ a b c d e f g h Porco, C. C.; Helfenstein, P.; Thomas, P. C.; Ingersoll, A. P.; Wisdom, J.; West, R.; Neukum, G.; Denk, T.; Wagner, R. (10 March 2006). "Cassini Observes the Active South Pole of Enceladus". Science. 311 (5766): 1393–1401. Bibcode:2006Sci...311.1393P. doi:10.1126/science.1123013. PMID 16527964. S2CID 6976648.
  3. ^ J. Perry (23 May 2005). "New Enceladus Raw Images". Retrieved 22 March 2006.
  4. ^ a b Spencer, J. R.; Pearl, J. C.; Segura, M.; Flasar, F. M.; Mamoutkine, A.; Romani, P.; Buratti, B. J.; Hendrix, A. R.; Spilker, L. J.; Lopes, R. M. C. (2006). "Cassini Encounters Enceladus: Background and the Discovery of a South Polar Hot Spot". Science. 311 (5766): 1401–1405. Bibcode:2006Sci...311.1401S. doi:10.1126/science.1121661. PMID 16527965. S2CID 44788825.
  5. ^ "New Names Approved for Use on Enceladus". SaturnToday.Com. SpaceRef Interactive Inc. 2006-11-17. Retrieved 2008-09-20. {{cite web}}: External link in |work= (help)
  6. ^ a b R. H. Brown et al., Science 311 1425 (2006).
  7. ^ Cassini Finds Enceladus Tiger Stripes are Really Cubs 2008-10-18 at the Wayback Machine. Retrieved March 22, 2006.
  8. ^ a b Dyches, Preston; Brown, Dwayne; et al. (July 28, 2014). "Cassini Spacecraft Reveals 101 Geysers and More on Icy Saturn Moon". NASA. Retrieved July 29, 2014.
  9. ^ NASA's Cassini Images Reveal Spectacular Evidence of an Active Moon 2011-10-29 at the Wayback Machine. 6 December 2005. Retrieved March 22, 2006.
  10. ^ . CICLOPS web site. NASA/JPL/GSFC/SwRI/SSI. 2008-03-26. Archived from the original on 2011-07-25. Retrieved 2009-08-30. {{cite web}}: External link in |work= (help)
  11. ^ Kieffer, Susan W.; Xinli Lu; et al. (2006). "A Clathrate Reservoir Hypothesis for Enceladus' South Polar Plume". Science. 314 (5806): 1764–1766. Bibcode:2006Sci...314.1764K. doi:10.1126/science.1133519. PMID 17170301. S2CID 41743663.
  12. ^ Battersby, Stephen (26 March 2008). "Saturn's moon Enceladus surprisingly comet-like". New Scientist. Retrieved 16 April 2015.
  13. ^ . NASA News. 14 April 2015. Archived from the original on 2015-04-16. Retrieved 2015-04-15.
  14. ^ Hedman, M. M.; Burns, J. A.; et al. (2012). "The three-dimensional structure of Saturn's E ring". Icarus. 217 (1): 322–338. arXiv:1111.2568. Bibcode:2012Icar..217..322H. doi:10.1016/j.icarus.2011.11.006. S2CID 1432112.
  15. ^ Vittorio, Salvatore A. (July 2006). . Cambridge Scientific Abstracts (CSA). CSA. Archived from the original on 2014-04-28. Retrieved 2014-04-27.
  16. ^ Baum, W. A.; Kreidl, T. (July 1981). "Saturn's E ring: I. CCD observations of March 1980". Icarus. 47 (1): 84–96. Bibcode:1981Icar...47...84B. doi:10.1016/0019-1035(81)90093-2.
  17. ^ Haff, P. K.; Eviatar, A.; et al. (1983). Haff, P. K.; Eviatar, A.; Siscoe, G. L. (eds.). "Ring and plasma: Enigmae of Enceladus". Icarus. 56 (3): 426–438. Bibcode:1983Icar...56..426H. doi:10.1016/0019-1035(83)90164-1.
  18. ^ Pang, Kevin D.; Voge, Charles C.; et al. (1984). "The E ring of Saturn and satellite Enceladus". Journal of Geophysical Research. 89: 9459–9470. Bibcode:1984JGR....89.9459P. doi:10.1029/JB089iB11p09459.
  19. ^ Blondel, Philippe; Mason, John (August 23, 2006). Solar System Update. Springer Science. pp. 241–243.
  20. ^ Spahn, F.; Schmidt, J; et al. (2006). "Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring". Science. 311 (5766): 1416–1418. Bibcode:2006Sci...311.1416S. CiteSeerX 10.1.1.466.6748. doi:10.1126/science.1121375. PMID 16527969. S2CID 33554377.
  21. ^ Cain, Fraser (5 February 2008). "Enceladus is Supplying Ice to Saturn's A-Ring". NASA. Universe Today. Retrieved 2014-04-26.

External links edit

  • Fountains of Enceladus – Moon of Saturn at Cosmic Secrets

January 01, 1970
tiger, stripes, enceladus, other, uses, tiger, stripes, tiger, stripes, enceladus, consist, four, parallel, linear, depressions, south, polar, region, saturnian, moon, first, observed, 2005, cassini, spacecraft, imaging, science, system, camera, though, seen, . For other uses see Tiger stripes The tiger stripes of Enceladus consist of four sub parallel linear depressions in the south polar region of the Saturnian moon 1 2 First observed on May 20 2005 by the Cassini spacecraft s Imaging Science Sub system ISS camera though seen obliquely during an early flyby the features are most notable in lower resolution images by their brightness contrast from the surrounding terrain 3 Higher resolution observations were obtained by Cassini s various instruments during a close flyby of Enceladus on July 14 2005 These observations revealed the tiger stripes to be low ridges with a central fracture 2 Observations from the Composite Infrared Spectrometer CIRS instrument showed the tiger stripes to have elevated surface temperatures indicative of present day cryovolcanism on Enceladus centered on the tiger stripes 4 Cassini view of Enceladus s south pole The tiger stripes from lower left to upper right are the Damascus Baghdad Cairo Alexandria and Camphor sulci Contents 1 Names 2 Appearance and geology 3 Composition 4 Cryovolcanism 5 Relation to E Ring of Saturn 6 References 7 External linksNames editThe name tiger stripes is an unofficial term given to these four features based on their distinctive albedo Enceladean sulci subparallel furrows and ridges like Samarkand Sulci and Harran Sulci have been named after cities or countries referred to in The Arabian Nights Accordingly in November 2006 the tiger stripes were assigned the official names Alexandria Sulcus Cairo Sulcus Baghdad Sulcus and Damascus Sulcus Camphor Sulcus is a smaller feature that branches off Alexandria Sulcus 5 Baghdad and Damascus sulci are the most active while Alexandria Sulcus is the least active Appearance and geology edit nbsp Composite map of the southern hemisphere of Enceladus 2007 Images from the ISS camera onboard Cassini revealed the 4 tiger stripes to be a series of sub parallel linear depressions flanked on each side by low ridges 2 On average each tiger stripe depression is 130 kilometers long 2 kilometers wide and 500 meters deep The flanking ridges are on average 100 meters tall and 2 4 kilometers wide Given their appearance and their geologic setting within a heavily tectonically deformed region the tiger stripes are likely to be tectonic fractures 2 However their correlation with internal heat and a large water vapor plume suggests that tiger stripes might be the result of fissures in Enceladus lithosphere The stripes are spaced approximately 35 kilometers apart The ends of each tiger stripe differ in appearance between the anti Saturnian and sub Saturnian hemisphere On the anti Saturnian hemisphere the stripes terminate in hook shaped bends while the sub Saturnian tips bifurcate dendritically 2 Virtually no impact craters have been found on or near the tiger stripes suggesting a very young surface age Surface age estimates based on crater counting yielded an age of 4 100 million years assuming a lunar like cratering flux and 0 5 1 million years assuming a constant cratering flux 2 Composition editAnother aspect that distinguishes the tiger stripes from the rest of the surface of Enceladus are their unusual composition Nearly the entire surface of Enceladus is covered in a blanket of fine grained water ice The ridges that surround the tiger stripes are often covered in coarse grained crystalline water ice 2 6 This material appears dark in the Cassini camera s IR3 filter central wavelength 930 nanometers giving the tiger stripes a dark appearance in clear filter images and a blue green appearance in false color near ultraviolet green near infrared images The Visual and Infrared Mapping Spectrometer VIMS instrument also detected trapped carbon dioxide ice and simple organics within the tiger stripes 6 Simple organic material has not been detected anywhere else on the surface of Enceladus The detection of crystalline water ice along the tiger stripes also provides an age constraint Crystalline water ice gradually loses its crystal structure after being cooled and subjected to the Saturnian magnetospheric environment Such a transformation into finer grained amorphous water ice is thought to take a few decades to a thousand years 7 Cryovolcanism editSee also Cryovolcano nbsp Enceladus South Pole Geyser basin August 10 2014 8 nbsp Enceladus South Pole Geysers spray water from many locations along the tiger stripes Observations by Cassini during the July 14 2005 flyby revealed a cryovolcanically active region on Enceladus centered on the tiger stripe region The CIRS instrument revealed the entire tiger stripe region south of 70 South latitude to be warmer than expected if the region were heated solely from sunlight 4 Higher resolution observations revealed that the hottest material near Enceladus south pole is located within the tiger stripe fractures Color temperatures between 113 and 157 kelvins have been obtained from the CIRS data significantly warmer than the expected 68 kelvins for this region of Enceladus Data from the ISS Ion and Neutral Mass Spectrometer INMS Cosmic Dust Analyser CDA and CIRS instruments show that a plume of water vapor and ice methane carbon dioxide and nitrogen emanates from a series of jets located within the tiger stripes 9 10 The amount of material within the plume suggests that the plume is generated from a near surface body of liquid water 2 Over 100 geysers have been identified on Enceladus 8 Alternatively Kieffer et al 2006 suggest that Enceladus geysers originate from clathrate hydrates where carbon dioxide methane and nitrogen are released when exposed to the vacuum of space by the fractures 11 Enceladus Cryovolcanism nbsp One possible scheme for Enceladus s cryovolcanism nbsp Possible origins of methane found in plumes through its subsurface ocean nbsp Chemical composition of the plumes of EnceladusRelation to E Ring of Saturn editPlumes from the moon Enceladus which seems similar in chemical makeup to comets 12 have been shown to be the source of the material in the E Ring 13 The E Ring is the widest and outermost ring of Saturn except for the tenuous Phoebe ring It is an extremely wide but diffuse disk of microscopic icy or dusty material The E ring is distributed between the orbits of Mimas and Titan 14 Numerous mathematical models show that this ring is unstable with a lifespan between 10 000 and 1 000 000 years therefore particles composing it must be constantly replenished 15 Enceladus is orbiting inside this ring in a place where it is narrowest but present in its highest density raising suspicion since the 1980s that Enceladus is the main source of particles for the E ring 16 17 18 19 This hypothesis was confirmed by Cassini s first two close flybys in 2005 20 21 nbsp nbsp View of Enceladus s orbit from the side showing Enceladus in relation to Saturn s E ring nbsp Enceladus orbiting within Saturn s E ring nbsp Enceladus geyser tendrils comparison of images a c with computer simulations nbsp Enceladus south polar region locations of most active tendril producing geysers nbsp Eruptions on Enceladus may seem to be discrete jets but may be curtain eruptions instead video animation References edit Drake Nadia 9 December 2019 How an Icy Moon of Saturn Got Its Stripes Scientists have developed an explanation for one of the most striking features of Enceladus an ocean world that has the right ingredients for life The New York Times Retrieved 11 December 2019 a b c d e f g h Porco C C Helfenstein P Thomas P C Ingersoll A P Wisdom J West R Neukum G Denk T Wagner R 10 March 2006 Cassini Observes the Active South Pole of Enceladus Science 311 5766 1393 1401 Bibcode 2006Sci 311 1393P doi 10 1126 science 1123013 PMID 16527964 S2CID 6976648 J Perry 23 May 2005 New Enceladus Raw Images Retrieved 22 March 2006 a b Spencer J R Pearl J C Segura M Flasar F M Mamoutkine A Romani P Buratti B J Hendrix A R Spilker L J Lopes R M C 2006 Cassini Encounters Enceladus Background and the Discovery of a South Polar Hot Spot Science 311 5766 1401 1405 Bibcode 2006Sci 311 1401S doi 10 1126 science 1121661 PMID 16527965 S2CID 44788825 New Names Approved for Use on Enceladus SaturnToday Com SpaceRef Interactive Inc 2006 11 17 Retrieved 2008 09 20 a href Template Cite web html title Template Cite web cite web a External link in code class cs1 code work code help a b R H Brown et al Science 311 1425 2006 Cassini Finds Enceladus Tiger Stripes are Really Cubs Archived 2008 10 18 at the Wayback Machine Retrieved March 22 2006 a b Dyches Preston Brown Dwayne et al July 28 2014 Cassini Spacecraft Reveals 101 Geysers and More on Icy Saturn Moon NASA Retrieved July 29 2014 NASA s Cassini Images Reveal Spectacular Evidence of an Active Moon Archived 2011 10 29 at the Wayback Machine 6 December 2005 Retrieved March 22 2006 Jet Spots in Tiger Stripes CICLOPS web site NASA JPL GSFC SwRI SSI 2008 03 26 Archived from the original on 2011 07 25 Retrieved 2009 08 30 a href Template Cite web html title Template Cite web cite web a External link in code class cs1 code work code help Kieffer Susan W Xinli Lu et al 2006 A Clathrate Reservoir Hypothesis for Enceladus South Polar Plume Science 314 5806 1764 1766 Bibcode 2006Sci 314 1764K doi 10 1126 science 1133519 PMID 17170301 S2CID 41743663 Battersby Stephen 26 March 2008 Saturn s moon Enceladus surprisingly comet like New Scientist Retrieved 16 April 2015 Icy Tendrils Reaching into Saturn Ring Traced to Their Source NASA News 14 April 2015 Archived from the original on 2015 04 16 Retrieved 2015 04 15 Hedman M M Burns J A et al 2012 The three dimensional structure of Saturn s E ring Icarus 217 1 322 338 arXiv 1111 2568 Bibcode 2012Icar 217 322H doi 10 1016 j icarus 2011 11 006 S2CID 1432112 Vittorio Salvatore A July 2006 Cassini visits Enceladus New light on a bright world Cambridge Scientific Abstracts CSA CSA Archived from the original on 2014 04 28 Retrieved 2014 04 27 Baum W A Kreidl T July 1981 Saturn s E ring I CCD observations of March 1980 Icarus 47 1 84 96 Bibcode 1981Icar 47 84B doi 10 1016 0019 1035 81 90093 2 Haff P K Eviatar A et al 1983 Haff P K Eviatar A Siscoe G L eds Ring and plasma Enigmae of Enceladus Icarus 56 3 426 438 Bibcode 1983Icar 56 426H doi 10 1016 0019 1035 83 90164 1 Pang Kevin D Voge Charles C et al 1984 The E ring of Saturn and satellite Enceladus Journal of Geophysical Research 89 9459 9470 Bibcode 1984JGR 89 9459P doi 10 1029 JB089iB11p09459 Blondel Philippe Mason John August 23 2006 Solar System Update Springer Science pp 241 243 Spahn F Schmidt J et al 2006 Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring Science 311 5766 1416 1418 Bibcode 2006Sci 311 1416S CiteSeerX 10 1 1 466 6748 doi 10 1126 science 1121375 PMID 16527969 S2CID 33554377 Cain Fraser 5 February 2008 Enceladus is Supplying Ice to Saturn s A Ring NASA Universe Today Retrieved 2014 04 26 External links editFountains of Enceladus Moon of Saturn at Cosmic Secrets Retrieved from https en 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