Pallene (moon)

Pallene

Cassiniimage of Pallene transiting Saturn on October 16, 2010
Discovery
Discovered by	Voyager 2(first discovery) Cassini Imaging Team
Discovery date	June 1, 2004 (second discovery byCassini-Huygens)
Designations
Designation	Saturn XXXIII
Pronunciation	/pəˈliːniː/
Named after	ΠαλλήνηPallēnē
Alternative names	S/1981 S 14 (first discovery) S/2004 S 2 (second discovery)
Adjectives	Pallenean/pælɪˈniːən/
Orbital characteristics
Epoch20 June 2004 (JD2453177.5)
Semi-major axis	212300km
Eccentricity	0.004
Orbital period (sidereal)	1.009549d
Inclination	0.1810°±0.0014°(to Saturn's equator)
Satellite of	Saturn
Group	Alkyonides
Physical characteristics
Dimensions	5.76 × 4.16 × 3.68km (±0.14 × 0.14 × 0.14km)
Mean diameter	4.46±0.14 km
Volume	46.5 km3
Mass	(1.15±0.40)×1013kg
Meandensity	0.251±0.075 g/cm3
Surface gravity	0.011–0.016 mm/s2
Escape velocity	0.0007 km/s at longest axis to 0.0009 km/s at poles
Synodic rotation period	synchronous
Axial tilt	zero

Pallene/pəˈliːniː/is a very smallnatural satelliteofSaturn.It is one of three small moons known as theAlkyonidesthat lie between the orbits of the largerMimasandEnceladus.It is also designatedSaturn XXXIII.

Discovery

Discovery imageof Pallene in 2004 from theCassiniprobe

Pallene was discovered by the Cassini Imaging Team in 2004, during theCassini–Huygensmission.It was given the temporary designationS/2004 S 2.In 2005, the name Pallene was provisionally approved by the IAU Division III Working Group for Planetary System Nomenclature,and was ratified at the IAU General Assembly in 2006. The name refers toPallene,one of theAlkyonides,the seven beautiful daughters of thegiantAlkyoneus.

After the discovery in 2004, it was realized that Pallene had been first photographed on August 23, 1981, by the space probeVoyager 2.It had appeared in a single photograph and had been provisionally namedS/1981 S 14and estimated to orbit 200,000 km from Saturn.Because it had not been visible in other images, it had not been possible to compute its orbit at the time, but recent comparisons have shown it to match Pallene's orbit.

Orbital characteristics

Pallene is visibly affected by a perturbing mean-longitude resonance with the much larger Enceladus, although this effect is not as large as Mimas's perturbations onMethone.The perturbations cause Pallene'sosculating orbitalelements to vary with an amplitude of about 4 km in semi-major axis, and 0.02° in longitude (corresponding to about 75 km). Eccentricity also changes on various timescales between 0.002 and 0.006, and inclination between about 0.178° and 0.184°.

Ring

Back-illuminated rings of Saturn as seen byCassinion 15 September 2006. The faint Pallene ring is visible at the bottom left as indicated.

In 2006, images taken in forward-scattered light by theCassinispacecraft enabled the Cassini Imaging Team to discover a faint dust ring around Saturn that shares Pallene's orbit, now named thePallene Ring.The ring has a radial extent of about 2,500 km. Its source is particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path.

Exploration

Pallene's crescent illuminated bySaturnshine,imaged byCassinion 14 September 2011

TheCassinispacecraft, which studied Saturn and its moons until September, 2017, performed a fly-by of Pallene on 16 October 2010, and 14 September 2011 at a distance of 36,000 kilometers (22,000 miles) and 44,000 kilometers respectively.

References

Sources

• "Cassini Imaging Science Team".Cassini Imaging Central Laboratory for OPerationS. Archived fromthe originalon 2011-05-20.Retrieved2012-01-01.
• "Moonmade Rings".Cassini Imaging Central Laboratory for OPerationS. October 11, 2006. Archived fromthe originalon 2012-02-05.Retrieved2012-01-01.
• Green, Daniel W. E. (April 14, 1995)."Possible Satellites of Saturn".IAU Circular.6162.Retrieved2012-01-01.
• Green, Daniel W. E. (August 16, 2004)."S/2004 S 1 and S/2004 S 2"(discovery).IAU Circular.8389:1.Bibcode:2004IAUC.8389....1P.Retrieved2012-01-01.
• Green, Daniel W. E. (January 21, 2005)."S/2004 S 1 and S/2004 S 2"(naming the moon).IAU Circular.8471.Retrieved2012-01-01.
• Green, Daniel W. E. (October 11, 2006)."Rings of Saturn (R/2006 S 1, R/2006 S 2, R/2006 S 3, R/2006 S 4)".IAU Circular.8759:1.Bibcode:2006IAUC.8759....1P.Retrieved2012-01-01.
• Hedman, M. M.;Murray, C. D.;Cooper, N. J.; Tiscareno, M. S.; Beurle, K.; Evans, M. W.; Burns, J. A. (2008-11-25). "Three tenuous rings/arcs for three tiny moons".Icarus.199(2): 378–386.Bibcode:2009Icar..199..378H.doi:10.1016/j.icarus.2008.11.001.ISSN0019-1035.
• "NASA Finds Saturn's Moons May Be Creating New Rings".Cassini Solstice Mission.JPL/NASA. October 11, 2006. Archived fromthe originalon February 12, 2012.Retrieved2012-01-01.
• Porco, C. C.; Baker, E.; Barbara, J.; Beurle, K.; Brahic, A.; Burns, J. A.; Charnoz, S.; Cooper, N.; Dawson, D. D.; Del Genio, A. D.; Denk, T.; Dones, L.; Dyudina, U.; Evans, M. W.; Giese, B.; Grazier, K.; Helfenstein, P.; Ingersoll, A. P.; Jacobson, R. A.; Johnson, T. V.; McEwen, A.; Murray, C. D.; Neukum, G.; Owen, W. M.; Perry, J.; Roatsch, T.; Spitale, J.; Squyres, S.; Thomas, P.; Tiscareno, M. (February 25, 2005). "Cassini Imaging Science: Initial Results on Saturn's Rings and Small Satellites".Science.307(5713): 1226–1236.Bibcode:2005Sci...307.1226P.CiteSeerX10.1.1.368.2642.doi:10.1126/science.1108056.PMID15731439.S2CID1058405.
• Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M. Jr. (2006)."The orbits of Saturn's small satellites derived from combined historic andCassiniimaging observations ".The Astronomical Journal.132(2): 692–710.Bibcode:2006AJ....132..692S.doi:10.1086/505206.
• Thomas, P. C. (July 2010)."Sizes, shapes, and derived properties of the saturnian satellites after the Cassini nominal mission"(PDF).Icarus.208(1): 395–401.Bibcode:2010Icar..208..395T.doi:10.1016/j.icarus.2010.01.025.Archived fromthe original(PDF)on 2018-12-23.Retrieved2015-09-04.
• Thomas, P. C.; Burns, J. A.; Tiscareno, M. S.; Hedman, M. M.; et al. (2013)."Saturn's Mysterious Arc-Embedded Moons: Recycled Fluff?"(PDF).44th Lunar and Planetary Science Conference.p. 1598.Retrieved2013-05-21.
• Thomas, P. C.; Helfenstein, P. (July 2020). "The small inner satellites of Saturn: Shapes, structures and some implications".Icarus.344:20.Bibcode:2020Icar..34413355T.doi:10.1016/j.icarus.2019.06.016.S2CID197474587.113355.

External links

• Media related toPalleneat Wikimedia Commons
• Pallene ProfilebyNASA's Solar System Exploration