bluuebunny/crossref_metadata_2025 huggingface dataset:
Variations in spectral reflectivity and vertical cloud structure of Jupiter’s Great Red Spot
Authors: Anguiano-Arteaga Asier , Pérez-Hoyos Santiago , Sánchez-Lavega Agustín
Published: October 2020

The Great Red Spot (GRS) of Jupiter is a large anticyclonic vortex present in the Jovian atmosphere. First observed in the XVII century, it is almost constantly located at 22°S. Since its discovery it has gradually decreased in size at an average rate of 170 km/year in longitude and 60 km/year in latitude. The nature of the chromophore species that provide its characteristic color to the GRS’s upper clouds and hazes is still largely unknown, as well as its creation and destruction mechanisms. During year 2019, the GRS began to lose some of this reddish material as a consequence of the interaction with other vortices present in nearby latitudes, raising serious doubts about its possible disappearance (Sánchez-Lavega et al., 2019).In this work we have analyzed images provided by the Hubble Space Telescope between 2015 and 2019, with a spectral coverage from the ultraviolet to the near infrared, including some methane absorption bands of different depths. These images have been calibrated in absolute reflectivity, and from them we have obtained the spectral variations in brightness that occur in different dynamically interesting regions of the GRS and its surroundings.The spectral reflectivity of the studied regions over the mentioned years has been analyzed using the NEMESIS radiative transfer code (Irwin et al., 2008). In this way it has been possible to retrieve the main features playing a key role in the spectral reflectivity of GRS’s upper clouds and hazes, such as particle size distribution, refractive indexes and optical thickness. At the same time, this analysis has provided the vertical distribution of particles for pressure levels above 1 bar, allowing a comparative study of its evolution over recent years.References-Irwin, P. G. J., Teanby, N. A., de Kok, R., Fletcher, L. N., Howett, C. J. A., Tsang, C. C. C., . . . Parrish, P. D. (2008, April). The NEMESIS planetary atmosphere radiative transfer and retrieval tool. Journal of Quant. Spec. and Radiative Transfer, 109, 1136-1150. doi: 10.1016/j.jqsrt.2007.11.006- Sánchez-Lavega, A., Iñurrigarro, P., Anguiano-Arteaga, A., Garcia-Melendo, E., Legarreta, J., Hueso, R., Sanz-Requena, J.F., Pérez-Hoyos, S.,  Mendikoa, I., Soria, M., Rojas, J.F. Jupiter’s Great Red Spot threatened along 2019 by strong interactions with close anticyclones, AGU Fall Meeting, P44A-01, San Francisco, 12 December 2019
Mixing region over a surface of cometary nucleus with small-scale inhomogeneities
Authors: Zakharov Vladimir , Bykov Nikolay , Rodionov Alexander , Ivanovski Stavro , Della Corte Vincenzo , Rotundi Alessandra , Fulle Marco , Marschall Raphael
Published: October 2020

In the present work we study the case when gas production Q of the nucleus is formed by the gas emission from a set of closely located (with interval L) spots (see Fig.1) with sizes li much smaller than the radius of the nucleus Rn. We study the structure of the flow in the mixing region for different combinations of li, L, Q and define parameters of the resulting uniform flow. Due to a large number of spots (i.e. L
Binary maps detailing the possibility of liquid water through deliquescence on Mars
Authors: Pál Bernadett , Kereszturi Ákos
Published: October 2020

One of the key elements in our search for extraterrestrial life is the availability of liquid water. Mars has been our primary target for finding life in the last decades, and the search for ancient life signs, possibly ideal terrains is still popular. In the history of the Red Planet there were presumably wetter periods [McKay et al., 1991], however on the surface of modern Mars there is little chance for the prolonged existence of larger water bodies. Theoretical models show a chance for ephemeral appearances [e.g. Brass, 1980, Kereszturi et al., 2009, Knauth and Burt, 2002, McEwen et al., 2014], while computational model results imply a microscopic scale (especially brines) emergence [e.g. Kossacki, 2008, Martínez and Renno, 2013, Möhlmann, 2004]. In this abstract we show the first results of our new research estimating the likelihood for surface perchlorate deliquescence on Mars. We simulated the surface temperature, atmospheric pressure and water vapor volume mixing ratio for Mars year 29 using the LMDZ GCM detailed in Hourdin et al. (2006), which is the second generation of the climate model developed in the LMD described in the works of Sadourny et al. (1984) and Forget et al. (1999). From the output of the model we calculated the relative humidity with respect to ice and with respect to liquid detailed in Pál et al. (2020). There is a chance for deliquescence if both the temperature and the relative humidity with respect to liquid are above the calcium-perchlorate (Ca(ClO4)2) salt-specific threshold [Toner et al., 2014]. According to the research of Rivera-Valentín et al. (2018) if the relative humidity with respect to ice greatly exceeds 1, nucleation is favored rather than brine formation. Using this method we estimated the possibility of deliquescence on a binary scale, where 0 means no chance and 1 means definite chance. The possibility of deliquescence on a binary scale at 1 AM local time on sol 315 (the middle of northern summer). There is a larger area around Acidalia Planitia, where we see definite chance between the late northern spring and early northern autumn. We see a less defined, but persistent probability in the southern region of Utopia Planitia. This is a snapshot from the annual studies. Averaged probabilites of calcium-perchlorate deliquescence through the Mars year 29 at 1 AM local time. There is a rather consistent possibility between Ls 120 - 315 in the northern hemisphere, as well a during the southern summer (Ls 450 - 550) in the southern upper latitudes.This work was supported by the EXODRILTECH project of ESA and the Excellence of Strategic R&D centers (GINOP-2.3.2-15-2016-00003) project of NKFIH, Hungary and the related H2020 fund, the COOP-NN-116927 project of NKFIH and the TD1308 Origins and evolution of life on Earth and in the Universe COST actions number 39045 and 39078. 
Exploring Venus internal structure by its tidal response
Authors: Saliby Christelle , Fienga Agnes , Spada Giorgio , Memin Anthony , Melini Daniele
Published: October 2020

    Tidal forces acting on a planet cause a deformation and mass redistribution in its interior, involving surface motions and variation in the gravity field, which may be observed in geodetic experiments. The change in the gravitational field of the planet, due to the influence of an external gravity field, described primarily by its tidal Love number k of degree 2 (denoted by k2) can be observed from analysis of a spacecraft radio tracking. The planet's deformation is linked to its internal structure, most effectively to its density and rigidity. Hence the tidal Love number k2 can be theoretically approximated for different planetary models, which means comparing the observed and theoretical calculation of k2 of a planet is a window to its internal structure.    The terrestrial planet Venus is reminiscent of the Earth twin planet in size and density, which leads to the assumption that the Earth and Venus have similar internal structures. In this work, with a Venus density profile computed by Aitta [2012] and assuming that the planet in question is in hydrostatic equilibrium, we investigate the elastic parameters of each of Venus major layers to calculate its tidal Love number k2. The calculation of k2 is done with ALMA, a Fortran 90 program by Spada [2008] for computing the tidal and load Love numbers using the Post-Widder Laplace inversion formula. After implementing the Andrade rheology to ALMA, we investigate several different rheologies for the mantle of Venus as Maxwell, Burgers and Andrade rheologies.      The tidal Love number k2 of Venus is of 0.3±0.024, depending on the mantle rheology and number of mantle layers. With a more heterogeneous model, equivalently a higher number of layers, difference of the k2 values between different mantle rheology models decreases. An Andrade rheology model has indeed an apparent transient phase which manifests after 10 years, this phase makes the transition between short-term (before 10 years) and long-term (after 100 years) gravity field deformation smoother than that of Maxwell and Burgers. The curve of k2 for Burgers rheology for a three layers model is relatively uneven, it gets smoother while adding more layers. From the tidal Love number k2, we also conclude the dissipation function Q-1 and the tide-induced phase lag ε of Venus. Finally we compare the values obtained for k2, Q-1and  with that of the work of different authors.References:
The dynamical history and current orbital constraints of a milestone ice giant planet orbiting a white dwarf
Authors: Veras Dimitri , Fuller Jim
Published: October 2020

Robust evidence of an ice giant planet shedding its atmosphere around the white dwarf WD J0914+1914 represents a milestone in exoplanetary science, allowing us to finally supplement our knowledge of white dwarf debris discs, minor planets and metal pollution with the presence of a major planet. Here, I discuss the possible dynamical origins of this planet, WD J0914+1914 b. The very young cooling age of the host white dwarf (13 Myr) combined with the currently estimated planet-star separation of about 0.07 au imposes particularly intriguing and restrictive coupled constraints on its current orbit and its tidal dissipation characteristics. The planet must have been scattered from a distance of at least a few au to its current location, requiring the current or former presence of at least one more major planet in the system in the absence of a hidden binary companion. I show that WD J0914+1914 b could not have subsequently shrunk its orbit through chaotic f-mode tidal excitation (characteristic of such highly eccentric orbits) unless the planet was or is highly inflated and possibly had partially thermally self-disrupted from mode-based energy release. I also demonstrate that if the planet is currently assumed to reside on a near-circular orbit at 0.07 au, then non-chaotic equilibrium tides impose unrealistic values for the planet's tidal quality factor. I conclude that WD J0914+1914 b either (i) actually resides interior to 0.07 au, (ii) resembles a disrupted `Super-Puff' whose remains reside on a circular orbit, or (iii) resembles a larger or denser ice giant on a currently eccentric orbit. Distinguishing these three possibilities strongly motivates follow-up observations. I will also analyse the prospects for exterior extant rocky asteroids, boulders, cobbles, and pebbles to radiatively drift inward past the planet due to the relatively high luminosity of this particularly young white dwarf, and I will place stability bounds on the gas disc formed from the planet's evaporated atmosphere.Caption: Demonstration that WD J0914+1914 b was very unlikely to have experienced high-eccentricity chaotic tidal evolution unless the planet is or was a highly inflated Super-Puff. The solid curves represent the minimum initial semimajor axes (y-axis) for which different types of planets would have experienced chaotic tidal evolution around the white dwarf for given orbital pericentres (x-axes). The vertical dashed lines are representative white dwarf tidal disruption radii for each type of planet, ordered from left to right in the same way as the solid curves. Because Super-Puffs are particularly vunerable to self-disruption through chaotic tides, current observations may be of a partially or fully disrupted ice giant. 
Evidence of Alfvénic Interactions in the Jovian Magnetosphere from the Juno Spacecraft
Authors: Lorch Christopher T.S , Ray Licia C. , Watt Clare E.J. , Wilson Robert J. , Bagenal Frances , Allegrini Frédéric
Published: October 2020

New insights provided by Juno energetic particle detector measurements indicate signatures of Alfvénic acceleration are more common than previously anticipated. Studies at Earth show that Alfvén waves can substantially accelerate plasma within the magnetosphere. At Jupiter, it is now predicted that Alfvénic acceleration is the dominant mechanism for generating the planet's powerful aurora. This acceleration occurs when the plasma thermal velocity is approximately equal to the Alfvén velocity, which at Jupiter occurs around the plasma sheet boundary. Using Juno JADE and MAG data, we investigate the regions surrounding the plasma sheet boundary layer in order to identify signatures of Alfvénic activity. Our study finds correlations between inertial scale magnetic field perturbations and variations in the local plasma population. We suggest that these signatures may be linked to turbulence in the plasma disk, which could be a source of heating for magnetospheric plasma observed in other studies.
Solar cycle dependence of solar wind coupling at the Ice Giants
Authors: Gershman Daniel , DiBraccio Gina
Published: October 2020

The dominant form of mass and energy transport between the Sun and the Ice Giant magnetospheres of Uranus and Neptune remains an open question.  Predictions based on theory suggest that a combination of the weaker internal magnetospheric plasma sources and significantly tilted magnetic dipole fields of Uranus and Neptune may enable increased solar wind-magnetospheric coupling. Much of this coupling is dependent on the local solar wind parameters, specifically the Alfvénic Mach number (MA). Despite predictions of transport driven by solar wind coupling, the Voyager 2 flyby of Uranus observed a large MA of ~23 and a loop-like plasmoid in the magnetotail, suggestive of more internal planetary plasma driving.  In order to better constrain the possible scenarios of internally-driven vs. externally-driven magnetospheric convection at a given planet, a quantitative assessment of upstream plasma variations is required. The interaction between the solar wind and a planetary magnetosphere is often parameterized in terms of MA, with lower values enabling enhanced rates of magnetopause reconnection and energy exchange between the interplanetary and planetary environments. Here we perform a comprehensive analysis of upstream MA throughout the solar system using data spanning from 0.3 AU to 75 AU, collected by the Helios 1 & 2, Voyager 1 & 2, and Pioneer 10 & 11 spacecraft from 1972-2005.  We find that systematic increases in solar wind magnetic pressure during periods of high solar activity lead to lower-than-expected MA upstream of the giant planets. These lower MA values combined with the significant tilt of the magnetic dipole axes at Uranus and Neptune likely result in amplified solar-wind-magnetospheric coupling at solar maximum. The results indicate that magnetospheric dynamics at Uranus and Neptune may be strongly dependent on solar cycle.
Cross-comparison of global simulation models applied to Mercury's dayside magnetosphere
Authors: Aizawa Sae , Griton Lea , Fatemi Shahab , Exner Willi , Deca Jan , Pantellini Filippo , Yagi Manabu , Heyner Daniel , Génot Vincent , André Nicolas , Amaya Jorge , Murakami Go , Usui Hideyuki
Published: October 2020

We present the first comparison of multiple global simulations of the solar wind interaction with Mercury’s dayside magnetosphere, conducted in the framework of the international collaborative project SHOTS - Studies on Hermean magnetosphere Oriented Theories and Simulations. Two magnetohydrodynamic and two hybrid simulation codes are used to investigate the global response of the Hermean magnetosphere to a northward-oriented interplanetary magnetic field. We cross-compare the results of the four codes for a theoretical case and a MESSENGER orbit with similar upstream plasma conditions. The models agree on bowshock and magnetopause locations at 2.1 ± 0.1 and 1.4 ± 0.08 Mercury planetary radii, respectively. The latter locations may be influenced by subtle differences in the treatment of the plasma boundary at the planetary surface. The predicted magnetosheath thickness varies less between the codes. Finally, we also sample the plasma data along virtual trajectories of BepiColombo’s Magnetospheric and Planetary Orbiter. Our ability to accurately predict the structure of the Hermean magnetosphere aids the analysis of the onboard plasma measurements of past and future magnetospheric missions.
Characterisation of Transneptunian Binaries in the HST Archive.
Authors: Smith Richard , Fraser Wesley , Fitzsimmons Alan
Published: October 2020

Binary Transneptunian Objects (TNOs) have remained virtually unaltered since the formation of the solar system. They can therefore provide valuable insights into the history and properties of objects from the outer solar system, such as object compositions and dynamical history, including the effects of planetary migration on primordial planetesimal populations. Benecchi et al. 2009 measured the colours of 23 TNO binaries using the Hubble Space Telescope (HST), reporting a strong correlation between primary-secondary F606W-F814W colours. Marsset et al. 2020 extended this work into the NIR, adding a further three TNO binary objects with accurate colour measurements made using the Gemini-North telescope which indicated a similar colour correlation in the infrared.   We aim to increase the number of binary TNOs with accurate NIR colour measurements by reprocessing data available in the HST archive using a consistent MCMC-based point spread function (PSF)-fitting algorithm. We explore both the position and brightness parameter space for the binary components. Tiny Tim (Krist et al., 2011) PSFs are generated for each component and planted in a model image that is compared with the HST archive image to identify best-fit PSF parameter values. These values are then used to produce and subtract a final model image, providing accurate likelihood estimates for the in-image position and photometric brightness of each component.   We will present the results of applying the algorithm to archival data of 24 known binaries, including both optical and NIR colour measurements of both binary components. We will also provide a measure of our sensitivity to binary component separations and brightness ratios. Our results will be compared to the correlated colours observed by Benecchi et al. (2009) and Marsset et al. (2020). References:S. D. Benecchi, K. S. Noll, W. M. Grundy, M. W. Buie, D. C. Stephens, andH. F. Levison. The correlated colors of transneptunian binaries. Icarus, 200(1):292–303, Mar 2009. doi: 10.1016/j.icarus.2008.10.025.J Krist, R Hook, and F Stoehr. 20 years of hubble space telescope opticalmodeling using tiny tim, 2011. URLhttps://doi.org/10.1117/12.892762.Micha ̈el Marsset, Wesley C. Fraser, Michele T. Bannister, Megan E. Schwamb, Rosemary E. Pike, Susan Benecchi, J. J. Kavelaars, Mike Alexandersen, Ying-Tung Chen, Brett J. Gladman, Stephen D. J. Gwyn, Jean-Marc Petit, and Kathryn Volk. Col-OSSOS: Compositional Homogeneity of Three KuiperBelt Binaries.The Planetary Science Journal, 1(1):16, June 2020. doi:10.3847/PSJ/ab8cc0.
Alfnoor: assessing the information content of Ariel's low resolution spectra with planetary population studies.
Authors: Mugnai Lorenzo V. , Pascale Enzo , Changeat Quentin , Al-Refaie Ahmed , Tinetti Giovanna
Published: October 2020

In the next decade the Ariel Space Telescope will provide the first statistical dataset of exoplanet spectra, performing spectroscopic observation of about 1000 exoplanets in the wavelength range 0.5→7.8 μm thanks to its Reconnaissance Survey. About one half of these 1000 targets will be then selected for more accurate observations with higher spectral resolution.We present a novel metric to assess the information content of the Ariel Reconnaissance Survey low resolution transmission spectra. The proposed strategy will not only allow us to select candidate planets to be re-observed in Ariel higher resolution Tiers, but also to classify exoplanets by their atmospheric composition and to put the basis for the statistical analysis of such a large exoplanetary sample.To test our metric we use Alfnoor, a new package combining the TauRex spectral modelling with the ArielRad payload performance model, to produce populations of hundreds of exoplanets matching those presented in the Ariel Mission Reference Sample. For each of the planets in the Ariel candidate targets list we create an atmosphere with a randomised quantity of H2O, CH4, CO2, NH3 and clouds. Our metric proves able to identify methane,  carbon  dioxide  and  water  rich  atmospheres in the cases of molecular abundances > 10−4 in mixing ratio,  but it shows its limits in separating water from ammonia. We compare our metric with four different Deep Learning algorithms, they show only ∼10% better performance in identifying the molecular content.
Low-energy ion bulk velocities and temperatures inside the diamagnetic cavity of comet 67P
Authors: Bergman Sofia , Stenberg Wieser Gabriella , Wieser Martin , Nilsson Hans , Williamson Hayley , Nemeth Zoltan , Johansson Fredrik
Published: October 2020

IntroductionComets are unique objects. Due to their varying distance to the Sun, and the resulting variation of the plasma environment, they provide a unique opportunity to study plasma processes and an objects interaction with the solar wind. The comet’s neutral coma is ionized through photoionization, electron impact ionization and charge exchange, creating a comet ionosphere. The newly born ions are initially cold and flowing with the neutral gas, but are eventually accelerated by the convective electric field of the solar wind and are incorporated into the solar wind flow, a process often referred to as mass loading. The solar wind is as a consequence slowed down and deflected, leading to the creation of a bow shock, a cometopause and, closest to the comet nucleus, a magnetic field free region. This region is known as the diamagnetic cavity. The diamagnetic cavity is filled with newly born low-energy ions. Pick up processes are unimportant in this region; instead the ions are accelerated radially outwards due to an ambipolar electric field. Also important in this region is the interaction with the neutral particles. After the visit of Giotto to comet 1P/Halley it was suggested that the collisional coupling of the ions to the neutrals is dominating in this region (e.g. Cravens, 1989), making the ions flow with the same velocity as the neutrals. The resulting ion-neutral drag force was suggested to be the force balancing the outside magnetic pressure at the contact surface. This picture may, however, have to be revised after Rosetta’s visit to comet 67P/Churyumov-Gerasimenko. Measurements indicate that the ions may not be coupled to the neutrals. Odelstad et al. (2018) found ion velocities in the diamagnetic cavity of 2-4 km/s, which is above the expected velocity of the neutral particles (
Ring dynamics around the Centaur Chariklo and the dwarf planet Haumea: effects of high-order resonances
Authors: Sicardy Bruno , Renner Stefan , El Moutamid Maryame
Published: October 2020

Narrow and dense rings have been detected around the small Centaur body Chariklo (Braga-Ribas et al. 2014), as well as around the dwarf planet Haumea (Ortiz et al. 2017).Both objects have non-axisymmetric shapes that induce strong resonant effects between the rotating central body with spin rate Ω and the radial epicyclic motion of the ring particles, κ. These resonances include the classical Eccentric Lindblad Resonances (ELR), where κ = m(n-Ω), with m integer, n being the particle mean motion. These resonances create an exchange of angular momentum between the body and the collisional ring, clearing the corotation zone, pushing the inner disk onto the body and repelling the outer part outside of the outermost 1/2 ELR, where the particles complete one orbital revolution while the body executes two rotations, i.e. n/Ω ~ 1/2 (Sicardy et al. 2019)Here I will focus on higher-order resonances. They may appear either by considering other resonances such as n/Ω ~ 1/3, or the same resonance as above (n/Ω ~ 1/2), but with a body that has a triaxial shape. In this case, the invariance of the potential under a rotation of π radians transforms the 1st-order 1/2 Lindblad Resonance into a 2nd order 2/4 resonance.Second-order resonances are of particular interest because they force a strong response of the particles near the resonance radius, in spite of the intrinsically small strength of their forcing terms. This stems from the topography of the associated resonant Hamiltonian, which possesses an unstable hyperbolic point at its origin.The width of the region where this strong response is expected will be discussed for both Chariklo's and Haumea's rings. The special case of the second-order 1/3 resonance will be discussed, as it appears that both ring systems are close to that resonance.This work is intended, among others, to pave the way for future collisional simulations of rings around non-axisymmetric bodies.

Braga-Ribas et al., 2014, Nature 508, 72Ortiz et al., 2017, Nature 550, 219Sicardy et al., 2019, Nature Astronomy 3, 146
The work leading to these results has received funding from the European Research Council under the European Community's H2020 2014-2020 ERC Grant Agreement n°669416 "Lucky Star"
Variability in the energetic electron bombardment of Ganymede
Authors: Liuzzo Lucas , Poppe Andrew , Paranicas Christopher , Nénon Quentin , Fatemi Shahab , Simon Sven
Published: October 2020

This study examines the bombardment of energetic magnetospheric electrons onto Ganymede as a function of Jovian magnetic latitude. We use the output from a hybrid model to constrain features of the electromagnetic environment during the G1, G8, and G28 Galileo encounters when Ganymede was far above, within, or far below Jupiter's magnetospheric current sheet, respectively. To quantify electron fluxes, we use a test-particle model and trace electrons at discrete energies between 4.5 keV ≤ E ≤ 100 MeV while exposed to these fields. For each location with respect to Jupiter's current sheet, electrons of all energies bombard Ganymede's poles with average number and energy fluxes of 1·108 cm-2 s-1 and 3·109 keV cm-2 s-1, respectively. However, precipitation is inhomogeneous: poleward of the open-closed field line boundary, fluxes are enhanced in the trailing (but reduced in the leading) hemisphere. Within the Jovian current sheet, closed field lines of Ganymede's mini-magnetosphere shield electrons below 40 MeV from accessing the equator. Above these energies, equatorial fluxes are longitudinally inhomogeneous between the sub- and anti-Jovian hemispheres, but the averaged number flux (4·103 cm-2 s-1) is comparable to the flux deposited by each of the dominant energetic ion species near Ganymede. When outside of the Jovian current sheet, electrons below 100 keV enter Ganymede's mini-magnetosphere via the downstream reconnection region and bombard the leading apex, while electrons of all energies are shielded from the trailing apex. Averaged over a synodic rotation, electron flux patterns agree with brightness features observed across Ganymede's polar and equatorial surface.
The power of PolyFiX at NOEMA: new insights into sulfur chemistry in DM Tau
Authors: Semenov Dmitry , Favre Cecile , Fedele Davide , Teague Richard , Dutrey Anne , Guilloteau Stephane , Henning Thomas , Smirnov-Pinchukov Grigorii
Published: October 2020

We performed a deep search for CCS, SO, SO2, OCS, H2S, H2CS and other molecules in the DM Tauprotoplanetary disk at 2mm with PolyFiX@NOEMA. With a beam of ~2''x1'' and a spectral resolution of 0.3 km/s,a high sensitivity of ~3.8 mJy/beam was achieved. We detected o-H2S, o-H2CS, and DNC (first time in DM Tau)as well as H13CO+, N2D+, and,  tentatively, HC3N. We have not detected SO2, our main target molecule. We used thenon-LTE radiative transfer code RADEX to derive disk-averaged column densities and their upper limits. These values,together with our previous ALMA CS data were used for disk chemical modeling. The presence of CS and the lack ofSO2 in the DM Tau disk molecular layer can only be reliably explained by the disk model with a non-solar gas-phase C/O ratioof ~1, supporting previous findings.
 
The AAVSO’s program: creating inclusive citizen science communities
Authors: Kafka Stella
Published: October 2020

The American Association of Variable Star Observers was formed in 1911 as a group of US-based amateur observers obtaining data in support of professional astronomy projects. Now, it has evolved into an International Association with members and observers from both the professional and non-professional astronomical community, actively supporting ground and space-based variable star projects. As such, the AAVSO’s main claim to fame is that it successfully engages backyard Astronomers, educators, students and professional astronomers in astronomical research, building inclusive international communities around its portfolio. I will present the main aspects of the association and how it has evolved with time to become a premium resource for variable star researchers. I will also discuss the various means that the AAVSO is using to support cutting-edge research, and give updates on the tools and resources that are now available to researchers worldwide.
Monitoring the Reactivity of Formamide on Amorphous SiO2 by In-Situ UV-Raman Spectroscopy and DFT Modeling
Authors: Pantaleone Stefano , Signorile Matteo , Balucani Nadia , Bonino Francesca , Martra Gianmario , Ugliengo Piero
Published: October 2020

Formamide has been recognized in the literature as a key species in the formation of the complex molecules of life, such as nucleobases. Furthermore, several studies reported the impact of mineral phases as catalysts for its decomposition/polymerization processes, increasing the conversion and also favoring the formation of specific products. Despite the progresses in the field, in situ studies on these mineral-catalyzed processes are missing. In situ UV-Raman characterization of the chemical evolution of formamide over amorphous SiO2 samples, selected as a prototype of silicate minerals, was performed. The experiments were carried out after reaction of formamide at 160 °C on amorphous SiO2 (Aerosil OX50) either pristine or pre-calcined at 450 °C, to remove a large fraction of surface silanol groups. Our measurements, interpreted on the basis of density functional B3LYP-D3 calculations (Figure 1), allow to assign the spectra bands in terms of specific complex organic molecules, namely, diaminomaleonitrile (DAMN), 5-aminoimidazole (AI), and purine, showing the role of the mineral surface on the formation of relevant prebiotic molecules.
Helios spacecraft data revisited: Detection of cometary meteoroid trails by in-situ dust impacts
Authors: Krüger Harald , Strub Peter , Sommer Max , Altobelli Nicolas , Kimura Hiroshi , Lohse Ann-Kathrin , Grün Eberhard , Srama Ralf
Published: October 2020

Cometary meteoroid trails exist in the vicinity of comets, forming fine structure of the interplanetary dust cloud. The trails consist predominantly of the largest cometary particles (with sizes of approximately 0.1 mm to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. In the 1970s two Helios spacecraft were launched towards the inner solar system. The spacecraft were equipped with in-situ dust sensors which measured the distribution of interplanetary dust in the inner solar system for the first time. When re-analysing the Helios data, Altobelli et al. (Astron. Astrophys., 448, 243-252, 2006) recognized a clustering of seven impacts, detected by Helios in a very narrow region of space at a true anomaly angle of 135 +/- 1 degrees, which the authors considered as potential cometary meteoroid trail particles. At the time, however, this hypothesis could not be studied further.We re-analyse these candidate cometary trail particles in the Helios dust data to investigate the possibility that some or all of them indeed  originate from cometary trails and we constrain their source comets.The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model is a new universal model for cometary meteoroid streams in the inner solar system, developed by Soja et al. (Astron. Astrophys., 583, A18, 2015). We use IMEX to study cometary trail traverses by  Helios. During ten revolutions around the Sun, the Helios spacecraft intersected 13 cometary meteoroid trails. For the majority of these traverses the predicted dust fluxes are very low. In the narrow region of space where Helios detected the candidate dust particles, however, the spacecraft repeatedly traversed the trails of comets 45P/Honda-Mrkos-Pajdusakova and 72P/Denning-Fujikawa with relatively high predicted dust fluxes. The analysis of the detection times and particle impact directions shows that four detected particles are compatible with an origin from these two comets. By combining measurements and simulations we find a dust spatial density in these trails of approximately 10^-8 to 10^-7 m^-3.The identification of potential cometary meteoroid trail particles in the Helios data greatly benefitted from the clustering of trail traverses in a rather narrow region of space. The in-situ detection and analysis of meteoroid trail particles which can be traced back to their source bodies by spacecraft-based dust analysers opens a new window to remote compositional analysis of comets and asteroids without the necessity to fly a spacecraft to or even land on those celestial bodies. This provides new science opportunities for future space missions like Destiny+, Europa Clipper and IMAP.
Io sodium jets observed by the TRAPPIST telescopes
Authors: Bonfond Bertrand , Jehin Emmunuel , Despiegeleire Amandine
Published: October 2020

Io is one of the most active bodies of the solar system, with an intense volcanism powered by tidal forces. Directly or indirectly, the outgassing from the volcanoes is the source of particles populating both the tenuous and patchy atmosphere of Io and the magnetosphere of Jupiter. We report here on the observations of Io with a narrow-band NaI filter on the TRAPPIST-south telescope (ESO La Silla, Chile) during 15 nights between December 4, 2014 and March 31, 2015. The images are strongly contaminated by Jupiter in the field of view. However, we developed and tested several image processing techniques to remove the background and reveil spectacular sodium jets. We detected these jets on 6 nights out of 15. We will discuss the main properties of these jets, such as their length, which can be up to 7 Jovian radii long.
Jovian auroral conductance from Juno-UVS: hemispheric asymmetry?
Authors: Gérard Jean-Claude , Gkouvelis Leonardos , Bonfond Bertrand , Gladstone Randy , Blanc Michel , Grodent Denis , Hue Vincent , Greathouse Thomas , Kammer Joshua , Verteeg Maarten
Published: October 2020

Ionospheric conductance is important in controlling the electrical coupling between the Jovian planetary magnetosphere and its ionosphere. To some extent, it regulates the characteristics of the ionospheric current from above and the closure of the magnetosphere-ionosphere circuit in the ionosphere (Cowley&Bunce, 2001). Multi-spectral images collected with the UltraViolet Spectrograph (UVS) (Gladstone et al., 2017) on board Juno (Bagenal et al.,2017) have been analyzed to derive the spatial distribution of the auroral precipitation reaching the atmosphere (Bonfond et al., 2017). Electron energy flux and their characteristic energy have been used as inputs to an ionospheric model providing the production and loss rates of the main ion species, H3+, hydrocarbon ions and electrons (Gérard et al., 2020). Their steady state densities are calculated and used to determine the local distribution of the Pedersen electrical conductivity and its altitude integrated value for each UVS pixel. These values are displayed as H3+ density and Pedersen conductivity maps. We find that the main contribution to the Pedersen conductance corresponds to collisions of H3+ and hydrocarbon ions with H2.Analysis of the Birkeland current intensities based on the Juno magnetometers measurements (Kotsiaros et al. 2019) indicated that the observed current intensities are statistically larger in the south. They suggested that these differences are possibly due to a higher Pedersen conductance in this hemisphere. In order to verify this hypothesis, we calculate the conductance and H3+ density maps for perijoves 1 to 15 based on Juno-UVS spectral images. We compare the spatially integrated auroral conductance values of the two hemispheres for each orbit.  The objective is to identify possible hemispheric asymmetries.   REFERENCESBagenal, F., et al. (2017). Magnetospheric science objectives of the Juno mission. Space Science Reviews, 213(1-4), 219-287.Bonfond, B., et al. (2017). Morphology of the UV aurorae Jupiter during Juno's first perijove observations. Geophysical Research Letters, 44(10), 4463-4471.Cowley, S.W.H. & Bunce, E.J. (2001). Origin of the main auroral oval in Jupiter’s coupled magnetosphere–ionosphere system. Planet. Space Sci. 49, 1067–1088.Gérard et al., Spatial distribution of the Pedersen conductance in the Jovian aurora from Juno-UVS spectral images, J. Geophys. Res., in press.Gladstone et al. (2017). The ultraviolet spectrograph on NASA’s Juno mission. Space Science Reviews, 213(1-4), 447-473.Kotsiaros, S. et al. (2019). Birkeland currents in Jupiter’s magnetosphere observed by the polar-orbiting Juno spacecraft. Nature Astronomy, 3(10), 904-909.
Juno Diagnosis of Magnetospheric Dynamics at Jupiter with Energetic Neutral Atoms
Authors: Mauk Barry , Clark George , Allegrini Frederic , Bagenal Fran , Bolton Scott , Connerney John , Haggerty Dennis , Kollmann Peter , Mitchell Donald , Paranicas Chris , Rymer Abigail
Published: October 2020

Energetic Neutral Atom (ENA) cameras on orbiting spacecraft at Earth and Saturn have helped greatly to diagnose these complex magnetospheres. Within this decade, the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) mission will arrive at Jupiter and make ENA imaging a major thrust in helping to understand its complex magnetosphere. The present polar-orbiting Juno mission carries no ENA camera, but the energetic particle JEDI instrument is serendipitously sensitive to ENA’s with energies > 50 keV, provided there are no charged particles in the environment to mask their presence. Juno offers great service to the interpretation of both past and future ENA imaging with its orbit allowing unique viewing perspectives. Here we report on several components of ENA emissions that can probe the dynamical state of the regions involved, including the space environment of the orbit of Io, that of Europa, and Jupiter itself. A special focus here will be new observations of ENA emissions from Jupiter’s polar regions, the proper interpretation of which may end up being unique to the Juno mission, even after the JUICE mission.
Testing the Ma_MISS instrument capabilities for organics detection
Authors: Ferrari Marco , De Angelis Simone , De Sanctis Maria Cristina , Altieri Francesca , Ammannito Eleonora , Frigeri Alessandro , Formisano Michelangelo , Mugnuolo Raffaele , Pirrotta Simone
Published: October 2020

AbstractLaboratory measurements were performed on different mixtures made with clays and organic compounds with the aim of characterizing the detection capabilities of biosignatures by the Ma_MISS (Mars Multispectral Imager for Subsurface Studies) instrument.IntroductionThe main scientific objectives of the ESA mission ExoMars2022 are searching for signs of past and/or present life on Mars and characterizing the subsurface geochemical environment as a function of depth. The Rosalind Franklyn rover [1] payload consists of a suite of nine instruments that will provide information about the geological and geochemical environment of the surface and subsurface of the selected landing site (i.e. Oxia Planum) [2]. Remote sensing measurements performed by OMEGA and CRISM suggest that the exposed rocks on the surface of Oxia Planum experienced an intense aqueous alteration [3]. The widespread presence of Fe/Mg-Al-phyllosilicates and, more generally, the presence of silicates containing OH confirm the interaction between water and mother rocks, which is a prerequisite favorable to the development of life. In this framework, we performed several spectroscopic measurements of clay minerals mixed with different organic compounds, to assess Ma_MISS capability of organic’s detection in the Martian subsurface.The Ma_MISS instrumentMa_MISS is the Visible- and Near-Infrared miniaturized spectrometer hosted in the drill system of the ExoMars2022 rover that will characterize the mineralogy and stratigraphy of the excavated borehole wall at different depths (
Statistical analysis of dust grain tracks in Rosetta/OSIRIS images
Authors: Lemos Pablo
Published: October 2020

In some of the images taken by OSIRIS, pieces of debris can be seen as bright tracks instead of points sources as result of the combination of movements of both particles and spacecraft. The properties of those tracks, such as orientation, length and total brightness, depend on various comets parameters, including the activity on the nucleus surface, capable of lifting and accelerating the particles, and the characteristics of dust grains, as grain sizes, spatial distribution, velocity, density and sensitivity to radiation pressure. Previous works have focused on retrieving some of these grain properties from the mentioned images, but since the images show the 2D projection of the 3D dust motion, they rely on different methods to obtain the distance between the camera and the debris.In this work, a new method to bypass this distance determination requirement is proposed. The main steps involved are (i) analyze a large set of images containing tracks generated by moving dust grains, and obtain distribution for selected track parameters (orientation, length, total brightness, etc.) using an algorithm based on the Hough transform method; (ii) compare these results with the ones obtained from artificial images, generated by modeling the three dimensional motion of the debris in the gas flow field of the comet, under the influence of gravity, radiation pressure and gaseous drag; (iii) iterate this process in order to refine the parameters characterizing the physical properties of the dust emission used by the model.
Comparison of Terrestrial and Martian TEC at Dawn and Dusk during Solstices
Authors: Burrell Angeline , Sánchez-Cano Beatriz , Witasse Olivier , Lester Mark , Cartacci Marco
Published: October 2020

Planetary ionospheres undergo many changes at dawn and dusk due to both photochemical and transport processes.  The relative importance of these different processes vary depending on a variety of factors, including the amount of solar radiation, the composition of the thermosphere, and the characteristics of any local magnetic fields.  This study uses the similarities between the ionospheres on Mars and Earth to examine the behaviour of the ionosphere at dawn and dusk.  It has notable implications for comparative aeronomy, as a solid understanding of ionospheric processes on planets with and without magnetic fields is important for characterising the environments of solar and exoplanets, as well as atmospheric evolution over long time scales.The amount of plasma present in the ionosphere was measuring using the total electron content (TEC), and grouped so that both solstices and different phases of the solar cycle could be examined.  To allow comparisons between the ionospheres of Mars and Earth, which differ greatly in density, the rate of change of TEC as a function of solar zenith angle was used to compare the plasma production and losses in the main layer of each planetary ionosphere.  Examination of the dawn and dusk TEC slopes shows that, to first order, the Martian slopes are symmetric while those at Earth are not.  This symmetry is interpreted as an indicator of photochemical equilibrium, and different reasons for deviations from symmetry were explored.  The presence or absence of a magnetic field played a large role in shaping plasma transport, with photochemical processes in both ionospheres behaving similarly in the absence of a magnetic field.  At Mars, it was found that transport processes were most important at solar maximum, while at Earth transport processes were most important at solar minimum. 
RAS200: bringing astronomy and geophysics to new audiences
Authors: Miller Steve , Kanani Sheila
Published: October 2020

This year sees the Royal Astronomical Society – the oldest learned society covering astronomy and geophysics in the world – celebrate its 200th anniversary. In the run up to 2020, the RAS initiated an outreach and engagement scheme aimed at bringing the society’s sciences to new audiences, those who might not normally attend public lectures, planetarium shows or even star-gazing evenings. Committing £1 million to the project, the RAS deliberately sought out new partners who would take it out of its comfort zone with a bottom-up funding scheme making up to £100k available for five-year projects. Competition for the funding was fierce with just 12 projects funded out of more than 150 applications. Starting in 2015, the Prince’s Trust has used astronomy to inspire young people who have had some of the hardest starts in life. Carers who hardly ever get a break from their duties are funded to spend weekends learning about the stars on the Scottish island of Coll. A new planetarium show using Holst’s classic “Planet Suite” and modern adaptations brings the heavens in Full-dome 360 animation to audiences via mobile planetaria. New courses for adults who missed out on their education first time round have been developed. And Welsh cultural festivals now resonate to poetry, dance and music inspired by astronomy. Starting two years later, geophysics is being used to engage football crowds with science, and prisoners are being helped maintain links with their families through astronomy. In Cornwall, Galway and South Africa, artworks, trails and exhibitions are taking astronomy out to local people. And young girls and women in the Girl Guides have new badges to work for. All of these projects, too, are being adapted to suit people on the autistic spectrum.  All projects are being evaluated and all publicised as widely as possible. 