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Cassini microwave observations provide clues to the origin of Saturn's C ring
Nicholson, P. D.; Hedman, M. M.; Janssen, M. A. +6 more
Despite considerable study, Saturn's rings continue to challenge current theories for their provenance. Water ice comprises the bulk of Saturn's rings, yet it is the small fraction of non-icy material that is arguably more valuable in revealing clues about the system's origin and age. Herein, we present new measurements of the non-icy material fra…
Noncircular features in Saturn's rings IV: Absolute radius scale and Saturn's pole direction
Nicholson, Philip D.; French, Richard G.; McGhee-French, Colleen A. +6 more
We present a comprehensive solution for the geometry of Saturn's ring system, based on orbital fits to an extensive set of occultation observations of 122 individual ring edges and gaps. We begin with a restricted set of very high quality Cassini VIMS, UVIS, and RSS measurements for quasi-circular features in the C and B rings and the Cassini Divi…
Decadal timescale variability of the Enceladus plumes inferred from Cassini images
Ingersoll, Andrew P.; Ewald, Shawn P.
The brightness of the Enceladus plumes varies with position in the satellite's eccentric orbit, with altitude above the surface, and with time from one year to the next. Hedman et al. (2013, hereinafter H13) were the first to report these variations. They used data from Cassini's Visible and Infrared Mapping Spectrometer (VIMS). Here we present br…
The near-surface methane humidity on Titan
Lora, Juan M.; Ádámkovics, Máté
We retrieve vertical and meridional variations of methane mole fraction in Titan's lower troposphere by re-analyzing near-infrared ground-based observations from 17 July 2014 UT (Ádámkovics et al., 2016). We generate synthetic spectra using atmospheric methane profiles that do not contain supersaturation or discontinuities to fit the observations,…
Boulder abundances and size-frequency distributions on Oxia Planum-Mars: Scientific implications for the 2020 ESA ExoMars rover
Quantin, Cathy; Pajola, Maurizio; Carter, John +4 more
This paper presents the abundances and the size-frequency distributions (SFD) of boulders identified on a sector of the prime landing site for the ExoMars 2020 rover, in Oxia Planum region. By means of a HiRISE image, boulders ≥ 1.75 m across have been identified and subdivided according to the two main Oxia Planum geological units: the Noachian c…
Venus cloud-tracked and doppler velocimetry winds from CFHT/ESPaDOnS and Venus Express/VIRTIS in April 2014
Widemann, Thomas; Donati, Jean-François; Machado, Pedro +3 more
We present new coordinated observations and measurements of the wind amplitude and its variability at Venus cloud-tops based on the two complementary techniques of Ground-based Doppler velocimetry (Widemann et al., 2007, 2008; Machado et al., 2012, 2014) and cloud-tracked winds using ESA Venus Express/ VIRTIS-M imaging at 0.38 µm (Drossart e…
Jupiter's auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra
Fletcher, L. N.; Irwin, P. G. J.; Orton, G. S. +4 more
Auroral processes are evident in Jupiter's polar atmosphere over a large range in wavelength (X-ray to radio). In particular, previous observations in the mid-infrared (5-15 µm) have shown enhanced emission from CH4, C2H2 and C2H4 and further stratospheric hydrocarbon species in spatial …
Analysis and modeling of remote observations of the martian hydrogen exosphere
Bertaux, J. -L.; Chaufray, J. -Y.; Clarke, J. T. +2 more
Past observations of the martian exosphere have given a wide range of values for the mean temperature and number density of the hydrogen population that occupies this uppermost layer. More recently, observations by HST and MEX have found large variations over short timescales exhibited by this layer, which have been attributed to seasonal effects.…
Interannual and seasonal changes in the south seasonal polar cap of Mars: Observations from MY 28-31 using MARCI
James, P. B.; Cantor, B. A.; Calvin, W. M.
The Mars Color Imager (MARCI) camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars Years (MY) and over the southern summer. We present the first analysis of this data for the southern seasonal cap evolution observed in MY 28, 29, 30…
Dynamics of aspherical dust grains in a cometary atmosphere: I. axially symmetric grains in a spherically symmetric atmosphere
Fulle, M.; Della Corte, V.; Rotundi, A. +3 more
In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. For the interpretations of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of the Stardust …