Neafrapus cassini strain:NA
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ABSTRACT:
PROVIDER: PRJNA963968 | ENA |
REPOSITORIES: ENA
Similar Datasets
Project description:Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012-13, which make the net change insignificant (0.1 ± 0.2%) during the period 2007-2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012-13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 ± 0.6% from 2.40 ± 0.01 W/m(2) in 2007 to 2.28 ± 0.01 in 2012-13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 ± 0.6% from 2.41 ± 0.01 W/m(2) in 2007 to 2.35 ± 0.01 W/m(2) in 2012-13. The solar constant at Titan decreased by ~13.0% in the same period 2007-2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget.
| S-EPMC4316193 | biostudies-other
Project description:The plumes of Enceladus are of interest both as a geophysical phemonenon, and as an astrobiological opportunity for sampling internal material. Here we report measurements of the total mass density (gas plus dust, a combination not reported before except in the engineering literature) deduced from telemetry of Cassini's Attitude and Articulation Control System (AACS), as the spacecraft's thrusters or reaction wheels worked to maintain the desired attitude in the presence of gas drag torques during close flybys. The drag torque shows good agreement with the water vapor density measured by other instruments during the E5 encounter, but indicates a rather higher mass density on other passes (E3,E14), possibly indicating variations in gas composition and/or gas:dust ratio. The spacecraft appears to have intercepted about 0.2 grams of material, on flyby E21 in October 2015 indicating a peak mass density of ~5.5×10-11 kgm-3, the highest of all the flybys measured (E3,E5,E7,E9,E14,E21).
| S-EPMC6278931 | biostudies-literature
Project description:Before Cassini, scientists viewed Saturn's unique features only from Earth and from three spacecraft flying by. During more than a decade orbiting the gas giant, Cassini studied the planet from its interior to the top of the atmosphere. It observed the changing seasons, provided up-close observations of Saturn's exotic storms and jet streams, and heard Saturn's lightning, which cannot be detected from Earth. During the Grand Finale orbits, it dove through the gap between the planet and its rings and gathered valuable data on Saturn's interior structure and rotation. Key discoveries and events include: watching the eruption of a planet-encircling storm, which is a 20- or 30-year event, detection of gravity perturbations from winds 9000 km below the tops of the clouds, demonstration that eddies are supplying energy to the zonal jets, which are remarkably steady over the 25-year interval since the Voyager encounters, re-discovery of the north polar hexagon after 25 years, determination of elemental abundance ratios He/H, C/H, N/H, P/H, and As/H, which are clues to planet formation and evolution, characterization of the semiannual oscillation of the equatorial stratosphere, documentation of the mysteriously high temperatures of the thermosphere outside the auroral zone, and seeing the strange intermittency of lightning, which typically ceases to exist on the planet between outbursts every 1-2 years. These results and results from the Jupiter flyby are all discussed in this review.
| S-EPMC8753610 | biostudies-literature
Project description:Titan's stratosphere exhibits significant seasonal changes, including break-up and formation of polar vortices. Here we present the first analysis of mid-infrared mapping observations from Cassini's Composite InfraRed Spectrometer (CIRS) to cover the entire mission (Ls=293-93°, 2004-2017) - mid-northern winter to northern summer solstice. The north-polar winter vortex persisted well after equinox, starting break-up around Ls∼60°, and fully dissipating by Ls∼90°. Absence of enriched polar air spreading to lower latitudes suggests large-scale circulation changes and photochemistry control chemical evolution during vortex break-up. South-polar vortex formation commenced soon after equinox and by Ls∼60° was more enriched in trace gases than the northern mid-winter vortex and had temperatures ∼20 K colder. This suggests early-winter and mid-winter vortices are dominated by different processes - radiative cooling and subsidence-induced adiabatic heating respectively. By the end of the mission (Ls=93°) south-polar conditions were approaching those observed in the north at Ls=293°, implying seasonal symmetry in Titan's vortices.
| S-EPMC7580802 | biostudies-literature
Project description:In June 2015, Cassini high-resolution images of Saturn's limb southwards of the planet's hexagonal wave revealed a system of at least six stacked haze layers above the upper cloud deck. Here, we characterize those haze layers and discuss their nature. Vertical thickness of layers ranged from 7 to 18?km, and they extended in altitude ?130?km, from pressure level 0.5?bar to 0.01?bar. Above them, a thin but extended aerosol layer reached altitude ?340?km (0.4?mbar). Radiative transfer modeling of spectral reflectivity shows that haze properties are consistent with particles of diameter 0.07-1.4??m and number density 100-500?cm-3. The nature of the hazes is compatible with their formation by condensation of hydrocarbon ices, including acetylene and benzene at higher altitudes. Their vertical distribution could be due to upward propagating gravity waves generated by dynamical forcing by the hexagon and its associated eastward jet.
| S-EPMC7210256 | biostudies-literature