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Exposure age of Saturn's A and B rings, and the Cassini Division as suggested by their non-icy material content
Nicholson, P. D.; Janssen, M. A.; Hayes, A. G. +4 more
Saturn's rings are composed primarily of water ice with a small fraction of non-icy constituents that are likely both intrinsic and extrinsic in origin. The intrinsic material is thought to be characteristic of the ring progenitor, while the extrinsic material is derived from the continual stream of hypervelocity impacting micrometeoroids that pol…
Sulfur dioxide in the Venus Atmosphere: II. Spatial and temporal variability
Vandaele, A. C.; Robert, S.; Montmessin, F. +18 more
The vertical distribution of sulfur species in the Venus atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets - SPI…
Compositional and structural constraints on the geologic history of eastern Tharsis Rise, Mars
Murchie, S. L.; Viviano-Beck, C. E.; Beck, A. W. +1 more
Identification and mapping of distinct compositional units using high-resolution orbital imagery of the walls of Valles Marineris, Mars, provide key structural and environmental constraints on the geologic history of the eastern Tharsis Rise. Our results corroborate an overall vertical structure of the upper crust consistent with that inferred fro…
Thermal structure of the upper atmosphere of Venus simulated by a ground-to-thermosphere GCM
López-Valverde, M. A.; Gilli, G.; González-Galindo, F. +5 more
We present here the thermal structure of the upper atmosphere of Venus predicted by a full self-consistent Venus General Circulation Model (VGCM) developed at Laboratoire de Météorologie Dynamique (LMD) and extended up to the thermosphere of the planet. Physical and photochemical processes relevant at those altitudes, plus a non-orographic GW para…
The thermal structure of the Venus atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles✰
Montmessin, Franck; Tanga, Paolo; Tellmann, Silvia +30 more
The Venus International Reference Atmosphere (VIRA) model contains tabulated values of temperature and number densities obtained by the experiments on the Venera entry probes, Pioneer Venus Orbiter and multi-probe missions in the 1980s. The instruments on the recent Venus Express orbiter mission generated a significant amount of new observational …
Mars sedimentary rock erosion rates constrained using crater counts, with applications to organic-matter preservation and to the global dust cycle
Kite, Edwin S.; Mayer, David P.
Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, > 104-crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via ste…
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,…