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Rationale for BepiColombo Studies of Mercury's Surface and Composition
Muinonen, Karri; Wurz, Peter; Massironi, Matteo +63 more
BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury's surface than the suite carried by NASA's MESSENGER spacecraft. Moreover, BepiColombo's data rate is substantially higher. This equips it to confirm, elaborate upon, …
Comparison of the Deep Atmospheric Dynamics of Jupiter and Saturn in Light of the Juno and Cassini Gravity Measurements
Stevenson, David J.; Iess, Luciano; Showman, Adam P. +4 more
The nature and structure of the observed east-west flows on Jupiter and Saturn have been a long-standing mystery in planetary science. This mystery has been recently unraveled by the accurate gravity measurements provided by the Juno mission to Jupiter and the Grand Finale of the Cassini mission to Saturn. These two experiments, which coincidental…
Four Distinct Pathways to the Element Abundances in Solar Energetic Particles
Reames, Donald V.
Based upon recent evidence from abundance patterns of chemical elements in solar energetic particles (SEPs), and, ironically, the belated inclusion of H and He, we can distinguish four basic SEP populations: (1) SEP1—pure "impulsive" SEPs are produced by magnetic reconnection in solar jets showing steep power-law enhancements of 1 ≤Z ≤56 ions vers…
On the Origin and Evolution of the Material in 67P/Churyumov-Gerasimenko
Morbidelli, Alessandro; Snodgrass, Colin; Altwegg, Kathrin +5 more
Primitive objects like comets hold important information on the material that formed our solar system. Several comets have been visited by spacecraft and many more have been observed through Earth- and space-based telescopes. Still our understanding remains limited. Molecular abundances in comets have been shown to be similar to interstellar ices …
Aurora in the Polar Cap: A Review
Frey, Harald U.; Kullen, Anita; Maggiolo, Romain +5 more
This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sun-aligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic fi…
Studying the Composition and Mineralogy of the Hermean Surface with the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) for the BepiColombo Mission: An Update
Hiesinger, H.; Maturilli, A.; Helbert, J. +10 more
Launched onboard the BepiColombo Mercury Planetary Orbiter (MPO) in October 2018, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is on its way to planet Mercury. MERTIS consists of a push-broom IR-spectrometer (TIS) and a radiometer (TIR), which operate in the wavelength regions of 7-14 µm and 7-40 µm, respectively. …
Outstanding Challenges of Exoplanet Atmospheric Retrievals
Barstow, Joanna K.; Heng, Kevin
Spectral retrieval has long been a powerful tool for interpreting planetary remote sensing observations. Flexible, parameterised, agnostic models are coupled with inversion algorithms in order to infer atmospheric properties directly from observations, with minimal reliance on physical assumptions. This approach, originally developed for applicati…
Quiet, Discrete Auroral Arcs—Observations
Marghitu, O.; Karlsson, T.; Andersson, L. +5 more
Quiet, discrete auroral arcs are an important and fundamental consequence of solar wind-magnetosphere interaction. We summarize the current standing of observations of such auroral arcs. We review the basic characteristics of the arcs, including occurrence in time and space, lifetimes, width and length, as well as brightness, and the energy of the…
Origin and Evolution of Cometary Nuclei
Blum, Jürgen; Morbidelli, Alessandro; Davidsson, Björn +1 more
One of the key goals of the Rosetta mission was to understand how, where and when comets formed in our solar system. There are two major hypotheses for the origin of comets, both pre-Rosetta: (1) hierarchical accretion of dust and ice grains in the Solar Nebula and (2) the growth of pebbles, which are then brought together by streaming instabiliti…
Cometary Nuclei—From Giotto to Rosetta
Keller, Horst Uwe; Kührt, Ekkehard
We will briefly recapitulate the beginning of modern cometary physic. Then we will assess the results of the cometary flyby missions previous to ESA's Rosetta rendezvous with comet 67P/Churyumov-Gerasimenko. Emphasis is given to the physical properties of cometary nuclei. We will relate the results of the Rosetta mission to those of the flybys. A …