The Cassini Extended Mission

Seal, David; Buffington, Brent

doi:10.1007/978-1-4020-9217-6_22

Cited by 9 publications

(7 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This also seems to be rather unlikely, however, given the relative consistency in the mass densities derived from the different parts of each wave. Fortunately, Cassini will perform experiments at the end of its mission in 2017 that should provide independent constraints on the ring's total mass (Seal and Buffington 2009;Spilker et al 2014) that can confirm or refute the results of this study.…”

Section: Discussionmentioning

confidence: 66%

The B-ring’s surface mass density from hidden density waves: Less than meets the eye?

Hedman

Nicholson

2016

Icarus

View full text Add to dashboard Cite

Saturn's B ring is the most opaque ring in our solar system, but many of its fundamental parameters, including its total mass, are not well constrained. Spiral density waves generated by mean-motion resonances with Saturn's moons provide some of the best constraints on the rings' mass density, but detecting and quantifying such waves in the B ring has been challenging because of this ring's high opacity and abundant fine-scale structure. Using a wavelet-based analyses of 17 occultations of the star γ Crucis observed by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft, we are able to examine five density waves in the B ring. Two of these waves are generated by the Janus 2:1 and Mimas 5:2 Inner Lindblad Resonances at 96,427 km and 101,311 km from Saturn's center, respectively. Both of these waves can be detected in individual occultation profiles, but the multi-profile wavelet analysis reveals unexpected variations in the pattern speed of the Janus 2:1 wave that might arise from the periodic changes in Janus' orbit. The other three wave signatures are associated with the Janus 3:2, Enceladus 3:1 and Pandora 3:2 Inner Lindblad Resonances at 115,959 km, 115,207 km and 108,546 km. These waves are not visible in individual profiles, but structures with the correct pattern speeds can be detected in appropriately phase-corrected average wavelets. Estimates of the ring's surface mass density derived from these five waves fall between 40 and 140 g/cm 2 , even though the ring's optical depth in these regions ranges from ∼ 1.5 to almost 5. This suggests that the total mass of the B ring is most likely between one-third and two-thirds the mass of Saturn's moon Mimas.

show abstract

Section: Discussionmentioning

confidence: 66%

The B-ring’s surface mass density from hidden density waves: Less than meets the eye?

Hedman

Nicholson

2016

Icarus

View full text Add to dashboard Cite

show abstract

“…Funding and spacecraft health permitting, the Cassini mission will continue through mid-2017, ending with destruction of the spacecraft in Saturn's atmosphere when its fuel is exhausted (Seal & Buffington 2009). Till then, Enceladus will continue to be a prime target, and the planned Cassini trajectory includes three more close flybys in 2015 as well as many distant observations of the plumes, surface, and south polar heat radiation.…”

Section: Future Explorationmentioning

confidence: 99%

Enceladus: An Active Ice World in the Saturn System

Spencer

Nimmo

2013

Annu. Rev. Earth Planet. Sci.

151

123

View full text Add to dashboard Cite

Enceladus, one of the mid-sized icy moons of Saturn, has an importance to planetary science far greater than its modest 504-km diameter would suggest. Intensive exploration of Enceladus by the Cassini Saturn orbiter has revealed that it is the only known icy world in the solar system with ongoing deep-seated geological activity. Active tectonic fractures at Enceladus's south pole, dubbed "tiger stripes," warmed by internal tidally generated heat, spew supersonic jets of water vapor, other gases, and ice particles into circum-Saturnian space. A subsurface saltwater sea probably exists under the south pole, between the ice shell and the silicate core. Because of evidence that liquid water is probably present at the jet sources, Enceladus is also of great astrobiological interest as a potential habitat for life. 693 Annu. Rev. Earth Planet. Sci. 2013.41:693-717. Downloaded from www.annualreviews.org Access provided by 2601:240:c480:6500:792d:5fff:12f:554d on 05/23/18. For personal use only.

show abstract

“…Our knowledge of the geological and thermal histories of these satellites was first shaped by the Voyager spacecraft, which provided an initial, cursory view of these objects during their flybys in 1980 and 1981 (Smith et al, 1981(Smith et al, , 1982Gehrels and Matthews, 1984;Morrison et al, 1986;Moore et al, 2004;Orton et al, 2009). The Cassini spacecraft, since its orbit insertion around Saturn in 2004 (Dougherty et al, 2009;Seal and Buffington, 2009) has greatly expanded our understanding of the surface geology and interiors of the satellites. A notable early discovery from Voyager imagery was that the floors of some craters on Enceladus, Dione and possibly Rhea had become uplifted since formation, a phenomenon attributed to viscous relaxation of the icy crusts of these bodies (Passey, 1983;Schenk, 1989;Moore et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Impact basin relaxation on Rhea and Iapetus and relation to past heat flow

White

Schenk

Dombard

2013

Icarus

View full text Add to dashboard Cite

a b s t r a c tEvidence for relaxation of impact crater topography has been observed on many icy satellites, including those of Saturn, and the magnitude of relaxation can be related to past heat flow (e.g. Moore, J.M., Schenk, P.M., Bruesch, L.S.). We use new global digital elevation models of the surfaces of Rhea and Iapetus generated from Cassini data to obtain crater depth/diameter data for both satellites and topographic profiles of large basins on each. In addition to the factor of three lower amplitude of global topography on Rhea compared to Iapetus, we show that basins on Iapetus >100 km in diameter show little relaxation compared to similar sized basins on Rhea. Because of the similar gravities of Rhea and Iapetus, we show that Iapetus basin morphologies can be used to represent the initial, unrelaxed morphologies of the Rhea basins, and we use topographic profiles taken across selected basins to model heat flow on both satellites. We find that Iapetus has only experienced radiogenic heat flow since formation, whereas Rhea must have experienced heat flow reaching a few tens of mW m À2 , although this heat flow need only be sustained for as little as several million years in order to achieve the observed relaxation magnitudes. Rhea experienced a different thermal history from Iapetus, which we consider to be primarily related to their different formation mechanisms and locations within the saturnian system. A recent model for the formation of Saturn's mid-sized icy satellites interior to and including Rhea (Charnoz, S. et al. [2011]. Icarus 216, 535-550) describes how Rhea's orbit would have expanded outwards after its accretion from a giant primordial ring, which would have instigated early heating through rapid despinning and tidal interaction with Saturn and other satellites. Rhea's basins would therefore be required to have formed within the first few tens of Myr of Rhea's formation in order to relax due of this heating, and if so may provide an important anchor point for Saturn system chronology. None of these heating mechanisms are viable for Iapetus in its isolated position far from Saturn, and as such it has remained dynamically inert since formation, confirming conclusions based on thermal modeling of Iapetus' interior. Rapid and complete relaxation and subsequent erosion by bombardment of a 'first generation' of large basins on Rhea is regarded as an explanation for the lower counts of large basins on Rhea relative to Iapetus, and the overall lower amplitude of topography on Rhea compared to Iapetus.

show abstract

The Cassini Extended Mission

Cited by 9 publications

References 5 publications

The B-ring’s surface mass density from hidden density waves: Less than meets the eye?

The B-ring’s surface mass density from hidden density waves: Less than meets the eye?

Enceladus: An Active Ice World in the Saturn System

Impact basin relaxation on Rhea and Iapetus and relation to past heat flow

Contact Info

Product

Resources

About