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Dust and Snow Cover on Saturn's Icy Moons
West, R. D.; Le Gall, A.; Bonnefoy, L. E.
The final analysis of the Cassini radar observations of Saturn's icy moons presented here shows that the exchange of material between the planet's dust rings and moons, which is specific to the Saturnian system, plays a key role in the current state of the airless satellite regolith. Far from Saturn, the vast debris ring from Phoebe progressively …
How Much of the Sediment in Gale Crater's Central Mound Was Fluvially Transported?
Fassett, Caleb I.; Thomson, Bradley J.; Buczkowski, Debra L. +2 more
The origin of the sedimentary mound within Gale crater, the landing site for the Mars Science Laboratory rover Curiosity, remains enigmatic. Here we examine the total potential contribution of fluvial material by conducting a volume-based analysis. On the basis of these results, the mound can be divided into three zones: lower, intermediate, and u…
Wave Activity in Jupiter's North Equatorial Belt From Near-Infrared Reflectivity Observations
Wong, Michael H.; Irwin, Patrick G. J.; Orton, Glenn S. +4 more
High spatial resolution images of Jupiter at 1.58-2.28 µm are used to track and characterize a wave pattern observed in 2017 at a planetocentric latitude of 14°N. The wave pattern has a wave number of 18 and spans ∼5° in latitude. One bright crest remains stationary in System III longitude, while the remaining crests move slowly westward. Th…
Magnetized Dust Clouds Penetrating the Terrestrial Bow Shock Detected by Multiple Spacecraft
Lai, H. R.; Russell, C. T.; Jia, Y. D. +1 more
Clouds of charged nanometer dust, produced in intra-meteoroid collisions and accelerated by the magnetized solar wind, twist the interplanetary magnetic field as they are accelerated. Depending on the cloud size, minutes to hours-long perturbations are observed by interplanetary spacecraft and have been termed interplanetary field enhancements (IF…
A Persistent, Large-Scale, and Ordered Electrodynamic Connection Between Saturn and Its Main Rings
Gurnett, D. A.; Dougherty, M. K.; Hospodarsky, G. B. +8 more
Auroral hiss emissions are ubiquitous in planetary magnetospheres, particularly in regions where electric current systems are present. They are generally diagnostic of electrodynamic coupling between conductive bodies, thus making auroral and moon-connected magnetic field lines prime locations for their detection. However, the role of Saturn's rin…
Observations and Impacts of the 10 September 2017 Solar Events at Mars: An Overview and Synthesis of the Initial Results
Holmström, M.; Luhmann, J. G.; Halekas, J. S. +8 more
On 10 September 2017, some of the strongest solar activity occurred in association with active region 12673 (AR2673), including an X-class solar flare and a fast coronal mass ejection. Although AR2673 was not centrally facing Mars, the activity impacted the local space weather conditions at Mars. We give an overview of observations obtained from t…
Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs
Le Mouélic, S.; Rodriguez, S.; Sotin, C. +15 more
Cassini observations of Titan's weather patterns over >13 years, almost half a Saturnian year, provide insight into seasonal circulation patterns and the methane cycle. The Imaging Science Subsystem and the Visual and Infrared Mapping Spectrometer documented cloud locations, characteristics, morphologies, and behavior. Clouds were generally mor…
Observations of the Proton Aurora on Mars With SPICAM on Board Mars Express
Rodriguez, L.; Montmessin, F.; Ritter, B. +2 more
We report observations of the proton aurora at Mars, obtained with the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph on board Mars Express between 2004 and 2011. This is a third type of UV aurora that is discovered on Mars, in addition to the discrete and diffuse nightside aur…
H+/O+ Escape Rate Ratio in the Venus Magnetotail and its Dependence on the Solar Cycle
Fedorov, A.; Barabash, S.; Futaana, Y. +3 more
A fundamental question for the atmospheric evolution of Venus is how much water-related material escapes from Venus to space. In this study, we calculate the nonthermal escape of H+ and O+ ions through the Venusian magnetotail and its dependence on the solar cycle. We separate 8 years of data obtained from the ion mass analyz…
MARSIS Observations of the Martian Nightside Ionosphere During the September 2017 Solar Event
Gurnett, D. A.; Halekas, J. S.; Kopf, A. J. +5 more
We present topside ionospheric sounding on the nightside of Mars during the September 2017 solar event by Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express along with complementary dayside observations from Mars Atmosphere and Volatile EvolutioN (MAVEN). The MARSIS and MAVEN observations during the event sug…