J/AJ/159/129ivo://CDS.VizieR/J/AJ/159/129doi:10.26093/cds/vizier.51590129CDSHedman M.M.Helfenstein P.Chancia R.O.Thomas P.Roussos E.,Paranicas C.Verbiscer A.J.2021-12-06T23:16:56Z2020-07-20T07:25:29ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frphotometrysolar-systemWe examine the surface brightnesses of Saturn's smaller satellites using a photometric model that explicitly accounts for their elongated shapes and thus facilitates comparisons among different moons. Analyses of Cassini imaging data with this model reveal that the moons Aegaeon, Methone, and Pallene are darker than one would expect given trends previously observed among the nearby mid-sized satellites. On the other hand, the trojan moons Calypso and Helene have substantially brighter surfaces than their co-orbital companions Tethys and Dione. These observations are inconsistent with the moons's surface brightnesses being entirely controlled by the local flux of E-ring particles, and therefore strongly imply that other phenomena are affecting their surface properties. The darkness of Aegaeon, Methone, and Pallene is correlated with the fluxes of high-energy protons, implying that high-energy radiation is responsible for darkening these small moons. Meanwhile, Prometheus and Pandora appear to be brightened by their interactions with the nearby dusty F-ring, implying that enhanced dust fluxes are most likely responsible for Calypso's and Helene's excess brightness. However, there are no obvious structures in the E-ring that would preferentially brighten these two moons, so there must either be something subtle in the E-ring particles's orbital properties that leads to asymmetries in the relevant fluxes, or something happened recently to temporarily increase these moons's brightnesses.2020AJ....159..129Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/159/129CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/136/257 : Saturn's satellites in 1995/97 (Harper+ 1999)J/A+A/383/296 : Saturnian Satellites positions (1996-2000) (Peng+, 2002)J/A+A/422/377 : 1997-2000 Saturn's satellites astrometry (Qiao+, 2004)J/A+A/485/293 : Events of Saturn satellites during 2009 equinox (Arlot+, 2008)J/AJ/136/2214 : Positions of Saturn & its satellites in 2002-2006 (Peng+,2008)J/A+A/493/1183 : Saturn major satellites obs. (1874-2007) (Desmars+, 2009)J/other/SoSyR/45.523 : CCD obs. of saturnian satellites (Grosheva+, 2011)J/A+A/572/A43 : Saturnian satellites Cassini ISS astrometry (Cooper+, 2014)J/A+A/575/A73 : Astrometry of Saturnian satellites 2004-12 (Tajeddine+, 2015)J/A+A/582/A8 : Astrometry of the main satellites of Uranus (Camargo+, 2015)J/AJ/149/27 : Cassini ISS astrometry of Saturnian satellites (Cooper+, 2015)J/ApJ/811/67 : Saturn's G and D68 rings ISS observations (Hedman+, 2015)J/other/KFNT/33.70 : Topocentric positions Saturn's moons (Yizhakevych+, 2017)J/A+A/610/A2 : Saturnian satellites Cassini ISS astrometry (Cooper+, 2018)J/A+A/614/A15 : Mars Express astrometric obs. of Martian moons (Ziese+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/159/129https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/159/129http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/159/129https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/159/129https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/159/129http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/159/129GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/AJ/159/129/clearfilterBrightness estimates from clear-filter imagesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameObserved satellitemeta.id;meta.maincharFileImage Filenamemeta.id;meta.filecharRadDistance between spacecraft and body centerkmpos.distance;pos.bodyrcdoublePhasePhase Angledegpos.phaseAngfloatS/CLatSub-spacecraft planetocentric latitudedegpos.framefloatS/CLonSub-spacecraft west longitudedegpos.framefloatSolLatSub-solar planetocentric latitudedegpos.framefloatSolLonSub-solar west longitudedegpos.framefloatAeffEffective area valuekm**2phys.areadoublee_Aeff? Statistical uncertainty in Aeff (G1)km**2stat.errordoublenullableAphys? Geometric cross sectionkm**2meta.id.cross;phys.atmol.crossSectiondoublenullableaPre1? Predicted scaled effective area (G2)km**2phys.areadoublenullableaPre0.75? Predicted scaled effective area (G2)km**2phys.areadoublenullableaPre0.5? Predicted scaled effective area (G2)km**2phys.areadoublenullableJ/AJ/159/129/colorBrightness estimates from color imagesFiltFiltermeta.id;instr.filtercharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameObserved satellitemeta.id;meta.maincharFileImage Filenamemeta.id;meta.filecharRadDistance between spacecraft and body centerkmpos.distance;pos.bodyrcfloatPhasePhase Angledegpos.phaseAngfloatS/CLatSub-spacecraft planetocentric latitudedegpos.framefloatS/CLonSub-spacecraft west longitudedegpos.framefloatSolLatSub-solar planetocentric latitudedegpos.framefloatSolLonSub-solar west longitudedegpos.framefloatAeffEffective area valuekm**2phys.areadoubleAphys? Geometric cross sectionkm**2meta.id.cross;phys.atmol.crossSectionfloatnullableaPre1? Predicted scaled effective area (G2)km**2phys.areafloatnullableaPre0.75? Predicted scaled effective area (G2)km**2phys.areafloatnullableaPre0.5? Predicted scaled effective area (G2)km**2phys.areafloatnullable