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Chemical interactions between Saturn's atmosphere and its rings
Kurth, W. S.; Mitchell, D. G.; Wahlund, J. -E. +25 more
The Pioneer and Voyager spacecraft made close-up measurements of Saturn's ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn's atmosphere from infalling material. The Cassini Io…
In situ collection of dust grains falling from Saturn's rings into its atmosphere
Postberg, Frank; Schmidt, Jürgen; Spahn, Frank +16 more
Saturn's main rings are composed of >95% water ice, and the nature of the remaining few percent has remained unclear. The Cassini spacecraft's traversals between Saturn and its innermost D ring allowed its cosmic dust analyzer (CDA) to collect material released from the main rings and to characterize the ring material infall into Saturn. We rep…
In situ measurements of Saturn’s ionosphere show that it is dynamic and interacts with the rings
Gurnett, D. A.; Persoon, A. M.; Kurth, W. S. +10 more
The ionized upper layer of Saturn’s atmosphere, its ionosphere, provides a closure of currents mediated by the magnetic field to other electrically charged regions (for example, rings) and hosts ion-molecule chemistry. In 2017, the Cassini spacecraft passed inside the planet’s rings, allowing in situ measurements of the ionosphere. The Radio and P…
Magnetic seismology of interstellar gas clouds: Unveiling a hidden dimension
Tassis, Konstantinos; Tritsis, Aris
Stars and planets are formed inside dense interstellar molecular clouds by processes imprinted on the three-dimensional (3D) morphology of the clouds. Determining the 3D structure of interstellar clouds remains challenging because of projection effects and difficulties measuring the extent of the clouds along the line of sight. We report the detec…
Dust grains fall from Saturn's D-ring into its equatorial upper atmosphere
Persoon, A. M.; Kurth, W. S.; Mitchell, D. G. +12 more
The sizes of Saturn's ring particles range from meters (boulders) to nanometers (dust). Determination of the rings' ages depends on loss processes, including the transport of dust into Saturn's atmosphere. During the Grand Finale orbits of the Cassini spacecraft, its instruments measured tiny dust grains that compose the innermost D-ring of Saturn…
A radiation belt of energetic protons located between Saturn and its rings
Livi, S.; Krupp, N.; Jones, G. H. +21 more
Saturn has a sufficiently strong dipole magnetic field to trap high-energy charged particles and form radiation belts, which have been observed outside its rings. Whether stable radiation belts exist near the planet and inward of the rings was previously unknown. The Cassini spacecraft's Magnetosphere Imaging Instrument obtained measurements of a …
India plans to land near moon's south pole
Bagla, Pallava
Sometime this summer, an Indian spacecraft orbiting over the moon's far side will release a lander. The craft will ease to a soft landing just after lunar sunrise on an ancient, table-flat plain about 600 kilometers from the south pole. There, it will unleash a rover into territory never before explored at the surface. That's the ambitious vision …
Data trove helps pin down the shape of the Milky Way
Clery, Daniel
On 25 April, hundreds of astronomers around the world got their hands on one of the biggest data dumps in the history of astronomy: the exact positions, motions, brightnesses, and colors of 1.3 billion stars in and around the Milky Way, gathered during the first 2 years of operation by the European Space Agency's €750 million Gaia satellite, launc…
Fast stars point to supernovae, black holes
Sokol, Joshua
On 25 April, the European Space Agency released a data set gathered by the Gaia satellite containing the motions, and much more, of 1.3 billion stars. Astronomers have immediately sifted the data for fast-moving stars. They are prized as forensic tools: When rewound, their trajectories point back to the violent events that launched them. Last week…
Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source
Rest, A.; Foley, R. J.; Shappee, B. J. +14 more
On 17 August 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves (GWs) emanating from a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) telescopes detected a gamma-ray transient, GRB 17081…