bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamical influence of a wide binary companion on giant planet migration
Authors: Roisin Arnaud , Libert Anne-Sophie
Published: October 2020

About half of the Sun-like stars are part of multiple-star systems. To date more than 100 planets are known moving around one stellar component of a binary star (S-type planets), with diverse eccentricities. These discoveries raise the question of their formation and long-term evolution, since the stellar companion can strongly affect the planet formation process. Here we study the dynamical influence of a wide binary companion on the (Type-II) migration of a single giant planet in the protoplanetary disk. Using a modified version of an N-body integrator adapted for binary star systems and adopting eccentricity and inclination damping formulae (derived from hydrodynamical simulations) to properly model the influence of the disk, we carried out more than 3500 numerical simulations with different initial configurations and study the dynamics of the systems up to 100 Myr. Particular attention is paid to the Lidov-Kozai resonance whose role is determinant for the evolution of the giant planet, although initially embedded in the disk, when the stellar companion is highly inclined. We highlight the high probability for the planet of experiencing, during the disk phase, a scattering event or an ejection due to the presence of the binary companion. We also show that a capture of the migrating planet in the Lidov-Kozai resonance is far from being automatic even when the binary companion is highly inclined, since only 10% of the systems actually end up in the resonance. Nevertheless, using a simplified quadrupolar hamiltonian approach, we point out that, for highly inclined binary companions, the dynamical evolutions are strongly affected by the Lidov-Kozai resonance islands, which create the pile-ups observed around – but not centred on – the pericenter values of 90° and 270° in the final distribution of the giant planets. The influence of the self-gravity of the disk on the previous results is finally discussed.
Identifying and Characterizing Local Gaps in Saturn’s Rings from Skewness of Cassini UVIS Stellar Occultation Data
Authors: Green Melody , Colwell Joshua , Lewis Mark , Parker Cassandra
Published: October 2020

The Ultraviolet Imaging Spectrograph (UVIS) high-speed photometer (HSP) aboard the Cassini spacecraft collected stellar occultation data for stars of various brightness and viewing geometries as they were occulted by Saturn’s rings. We calculate the variance and skewness of the occultation light curves, and we analyze these statistical moments as functions of both optical depth and ring plane radius. Typical radial resolution of the occultations is 10-20 meters allowing for statistical moments to be calculated from 1000 points at 10 km radial sampling in the rings. We derived an analytic expression for skewness (S) as a function of optical depth assuming a ring composed of identical spherical particles, analogous to the normalized excess variance (E) relationship to optical depth used by Showalter and Nicholson (1990) and Colwell et al. (2018) to determine an effective particle size across the rings. We compared the results for effective particle size derived from S and E. Some regions, such as the inner B ring, return similar R-effective values, while others, such as the C ring plateaus, show distinctly different values. Skewness is a measure of the asymmetry of the distribution of photon counts in a measurement sample, while the variance is related to the spread of the distribution. Thus, agreement in the derived values of R-effective from S and E indicates an absence of clumps or local holes (nicknamed “ghosts”) in the rings that would lead to unusually small or large values of S, respectively. Regions of the rings where the values of R-effective from skewness (R_S) disagree with those derived from E (R_E) thus indicate the presence of ghosts or clumps that skew the distribution of photon counts in those regions. We use Monte-Carlo simulations of a simplified ring system composed of identical spherical particles interspersed with clumps and ghosts to determine the effects of these phenomena on S and compare to data. We also use simulated occultations through N-body simulations of the rings to calculate E and S where ghosts due to small moonlets or boulders are prevalent. We find variations in the suggested number of ghosts, presumed to be openings due to the same phenomena that create propeller structures in the A ring, across the rings, including in regions where there are no obvious optical depth signatures. 
Thermal conductivity of salt-bearing ice analogs in Jovian moons to support future JUICE mission.
Authors: González Díaz Cristóbal , M. Muñoz Caro Guillermo , Carrascosa de Lucas Héctor , Aparicio Secanellas Sofía , González Hernández Margarita , Anaya Velayos José J. , Anaya Catalán Guillermo , Prieto-Ballesteros Olga , Muñoz-Iglesias Victoria , Ercilla Herrero Oscar , Sánchez-Benítez Javier , Rivera-Calzada Alberto , Lorente Rosario , Altobelli Nicolas , Solomonidou Anezina , Vallat Claire , Witasse Olivier
Published: October 2020

Thermal properties of frozen salt solutions are crucial to interpret the JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper (NASA) missions, which will be launched in the upcoming years to make detailed observations of the giant gaseous planet Jupiter and three of its largest moons (Ganymede, Callisto, and Europa) due to the scarcity of experimental measurements.Therefore, we have conducted a set of experiments to measure and study the thermal conductivity and calorimetry of macroscopic frozen salt solutions of particular interest in these regions, including Na-chloride (NaCl), Mg-sulphate (MgSO4), sodium sulphate (Na2SO4), and Magnesium chloride (MgCl2). A climatic chamber has been used to mimic the cryogenic conditions in the Jovian Icy Moons. Measurements were performed at atmospheric pressure and temperatures from 0 to -70ºC. Temperature and thermal conductivity were measured during the course of the experiments. A side effect of these measurements is that they served to spot phase changes in the ice mixtures. A small sample of the liquid salt-water solution was set aside for the calorimetry measurements.These experiments and the measurements of thermal conductivity and calorimetry will be valuable to constrain the chemical composition, physical state, and temperature of the upper layers of the icy crusts of Ganymede, Callisto, and Europa (please see abstracts EPSC Muñoz Iglesias et al. 2020 and EPSC Solomonidou et al. 2020).
Upstream Ultra-Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock
Authors: Romanelli Norberto , DiBraccio Gina , Gershman Daniel , Le Guan , Mazelle Christian , Meziane Karim , Boardsen Scott , Slavin James , Raines Jim , Glass Austin , Espley Jared
Published: October 2020

In this work we perform the first statistical analysis of the main properties of waves observed in the 0.05–0.41 Hz frequency range in the Hermean foreshock by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Magnetometer. Although we find similar polarization properties to the '30 s' waves observed at the Earth's foreshock, the normalized wave amplitude (∼0.2) and occurrence rate (∼0.5%) are much smaller. This suggests significant lower backstreaming proton fluxes, due to the relatively low solar wind Alfvenic Mach number around Mercury. These differences could also be related to the relatively smaller foreshock size and/or more variable solar wind conditions. Furthermore, we estimate that the speed of resonant backstreaming protons in the solar wind reference frame (likely source for these waves) ranges between 0.95 and 2.6 times the solar wind speed. The closeness between this range and what is observed at other planetary foreshocks suggests that similar acceleration processes are responsible for this energetic population and might be present in the shocks of exoplanets.
The Colour Distribution Of The Low Inclination Trans-Neptunian Objects
Authors: Fraser Wesley , Kavelaars Jj , Bannister Michele , Marsset Michael , Schwamb Megan , Buchanan Laura , Smith Richard , Pike Rosemary , Benecchi Susan , Lehner Matthew , Wang Shiangyu , Peixinho Nuno
Published: October 2020

The low-inclination component of the classical Kuiper Belt is thought to be the only population of trans-Neptunian bodies that formed in-situ (Parker et al., 2010). This population, often referred to as the cold classical objects, exhibits a  ~30% observed binary fraction, much higher than for other trans-Neptunian objects (TNOs; Noll et al., 2008). The majority of cold classicals belong to the Very Red (VR) class of the bimodal TNO compositional taxonomy (Fraser and Brown, 2012). Though recently, a population of Less Red (LR) members has been identified, exhibiting a 100% binary fraction (Fraser et al., 2017). These so-called blue binaries are thought to be survivors of a push-out process that occurred during a smooth phase of Neptune’s outward migration. Here we report 20 new (g-r) and (r-J) colours of cold classical objects gathered as part of the Colours of the Outer Solar System Origins Survey (Col-OSSOS; Schwamb et al., 2019), bringing the total sample of cold classicals with measured colours to 21 with simultaneous optical and NIR colours, and 103 cold classical TNOs with optical colours alone. In this sample, 29 objects have been identified as binary (Parker, A., personal communication).Cold classical colours span the full range of optical-NIR colours exhibited by the dynamically excited TNO populations, though they strongly favour red objects;  the VR:LR ratio is ~12 compared to ~3 for the excited TNOs. Moreover, the VR cold classicals have a redder colour distribution than the VR excited TNOs, with the former exhibiting a mean (g-r)~0.95 and the latter, a mean (g-r)~0.8.The optical colour distribution of binary cold classicals is significantly different than that of the single (or unresolved) cold classical systems (see Figure 1), with the binary sample exhibiting a tail of lower spectral slopes than is found in the sample of singles. The Kolmogorov-Smirnov test comparing the optical colour distributions of the single and binary samples says that there is a only a 0.3% chance the two samples share the same colour distribution. The Col-OSSOS sample on its own shows a similar result, with a 2% probability of the null hypothesis. This argues for a different origin of some or all of the binary cold classicals over the unresolved or single objects population, and is compatible with the hypothesis that the blue binaries are contaminants having been pushed out from regions closer to the Sun. Figure 1: cumulative optical colour distributions of the single (or unresolved; solid) and binary (dashed) cold classical TNOs. The vertical line demarks the division between less red and very red compositional classes. Spectral slope is reported in percent reddening per 100 nm normalized in the V-band.
Remote 3D geological analysis of possible sedimentary layer geometries in upper Aeolis Mons, Gale Crater, Mars
Authors: Persaud Divya M , Barnes Robert , Tao Yu , Muller Jan-Peter
Published: October 2020

3D terrain models from high-resolution orbital imagery, such as that from HiRISE and CTX, provide an opportunity to probe the geologic history of Gale Crater, Mars, and contextualise observations from the Mars Science Laboratory. 3D HiRISE datasets of a channel in Gale Crater are visualised in the Planetary Robotics 3D Viewer (PRo3D) [1]. Digitised measurements of layers exposed in the channel are extracted using this software and analysed to investigate the depositional history of the central mound.

A 1-m HiRISE digital terrain model (DTM) was retrieved from University of Arizona Chicago [2] and co-registered to an 18-m CTX DTM, itself processed with CASP-GO [3] in [4], using the NASA Ames Stereo Pipeline [5]. This 3D dataset, in addition to a 25-cm HiRISE orthorectified image (ORI), was converted to the Ordered Point Cloud (OPC) format for visualisation in PRo3D.

The 3D scene was then analysed in the PRo3D suite. This investigation includes identifying sets or “packages” of beds, their relationships (e.g. unconformities, repeated sequences, erosion), quantifying their geometries (package thickness, dip/strike), observation of how these relationships change vertically within a package and along the channel, and the generation of summary logs of these sequences. These data are compared (a) across the channel, (b) with a CRISM covering part of the channel, and (c) with depositional models of the central mound of Aeolis Mons, and implications are discussed.

[1] Barnes, R., et al., ESS 5, 2018. [2] http://hirise.lpl.arizona.edu/ [3] Tao et al., PSS 154, 2018 [4] Persaud, D.M., et al., EPSC, abs. #1540, 2019. [5] Beyer, R., et al., ESS 5, 2018
Implantation of ions escaping the atmosphere of Mars within the regolith of Phobos, and Phobos’ surface ion weathering
Authors: Nénon Quentin , Poppe Andrew R , Rahmati Ali , McFadden James P
Published: October 2020

Mars has lost and is losing its atmosphere into space. Strong evidences of this come from the observation of planetary singly charged heavy ions (atomic oxygen, molecular oxygen, carbon dioxide ions) by Mars Express and MAVEN. Phobos, the closest moon of Mars, orbits only 6,000 kilometers above the red planet’s surface and is therefore a unique vantage point of the planetary atmospheric escape, with the escaping ions being implanted within the regolith of Phobos and altering the properties of the moon’s surface.In this presentation, we aggregate all ion observations gathered in-situ close to the orbit of Phobos by three ion instruments onboard MAVEN, from 2015 to 2019, to constrain the long-term averaged ion environment seen by the Martian moon at all longitudes along its orbit. In particular, the SupraThermal and Thermal Ion Composition (STATIC) instrument onboard MAVEN distinguishes between solar wind and planetary ions. The newly constrained long-term ion environment seen by Phobos is combined with numerical simulations of ion transport and effects in matter.This way, we find that planetary ions are implanted on the near side of Phobos (pointing towards Mars) inside the uppermost tens of nanometers of regolith grains. The composition of near-side grains that may be sampled by future Phobos sample return missions is therefore not only contaminated by planetary ions, as seen in lunar samples with the terrestrial atmosphere, but may show a unique record of the past atmosphere of Mars.The long-term fluxes of planetary ions precipitating onto Phobos are so intense that these ions weather the moon’s surface as much as or more than solar wind ions. In particular, Martian ions accelerate the long-term sputtering and amorphization of the near side regolith by a factor of 2. Another implication is that ion weathering is highly asymmetric between the near side and far side of Phobos.
Rotational properites of transneptunian objects from the K2 mission
Authors: Kiss Csaba , Kecskeméthy Viktória , Szakáts Róbert , Pál András , Molnár László , Sárneczky Krisztián , Vinkó József , Szabó Róbert , Szabó Gyula M. , Marton Gábor , Kiss László L.
Published: October 2020

Due to their faintness light curves of transneptunian objects (TNOs) in most cases are difficult to obtain, and therefore the number of TNOs with known rotational properties (at least rotation period) are rather limited. As it was shown for other small body populations, long-term, 1-3-month monitoring of small bodies revealed many targets with long rotation periods. These measurements significantly increased the number of slow rotators (P > 24h) for Jovian Trojans (Szabó et al., 2017), Hildas (Szabó et al., 2020) and Centaurs (Marton et al., 2020) using Kepler/K2 measurements, and also for main belt asteroids (Pál et al., 2020) using the TESS space telescope. Here we report on Kepler/K2 measurements of 70 TNOs, collected over the whole length of the K2 mission, in Campaigns 3-19. Our data notably increases the number of TNOs with known rotational properties. We compare these characteristics with those of other small body populations in the Solar system.Figure 1: Light curve of (50000) Quaoar obtained from the K2 measurements, folded with the canonical P = 8.84 h period (Ortiz et al., 2003, left), and with the newly determined P = 8.88h rotation period (right). References: - Marton, G., et al., 2020, Icarus, 345, 113721 - Ortiz, J.L., et al., 2003, A&A, 409, L13- Pál, A., et al., 2020, ApJS, 247, 26 - Szabó, Gy. et al., 2017, A&A, 599, A44 - Szabó, Gy. et al., 2020, ApJS, 247, 34
Search for Martian Schumann Resonances
Authors: Yu Yanan , Russell Christopher , Chi Peter , Haider Syed , Pabari Jayesh , Luhmann Janet
Published: October 2020

On Earth, electric discharges in thunderstorms produce ELF waves in the Earth-ionosphere waveguide that circles the globe. These waves give rise to Schumann resonances in the waveguide resonant cavity. These waves are also expected to occur at Venus, produced by strong lightning in the Venus atmosphere and at Mars produced by active dust devils or dust storms, during southern hemisphere summer, when the planet is near periapsis. Within dust storms, dust particles undergo triboelectric charging. The charge transfer leads to charge separation. A lightning discharge is expected to occur when the charge exceeds the breakdown strength of the media present. The transient electric discharge emits electromagnetic waves in the VLF/ELF range of frequency, leading to Schumann Resonance in the surface-ionospheric cavity. In a heterogeneous cavity, Schumann resonance modes are observable using an in-situ instrument. Recently has it been possible to search for these electromagnetic waves from the Mars surface using the UCLA-provided InSight fluxgate magnetometer. The weakness of the vertical component of ULF waves at Mars suggests that the subsurface is electrically conducting, allowing trapping of electromagnetic energy between the sub-surface and the ionosphere. The fundamental mode of Schumann resonance carries higher energy compared to there are more chances of observing the fundamental mode. Various values of the first mode are predicted in the literature for Mars like 13-14 Hz or between 9-14 Hz and 17.5 Hz. Even if the fundamental mode is above 10 Hz, the 20 Hz sampling rate will allow detection of an aliased signal. We examine the data obtained during Martian sandstorms for the possible existence of such waves. A large dust storm was detected on Mars beginning on InSight sols 40 to 50, and ending during sols 50 to 90. Examining the 20 Hz InSight magnetometer data during this period reveals no clearly identifiable Schumann Resonance signals within the bandwidth of the magnetometer.
Gaia DR2: orbit improvement based on new debiasing of asteroid astrometry
Authors: Tanga Paolo , Spoto Federica , Joao Ferreira , Pedro Machado
Published: October 2020

Gaia DR2, validating the debiasing of asteroid astrometry by orbit improvementThe optimal exploitation of asteroid astrometry is seminal at many tasks such as the monitoring of impact risks by potentially hazardous asteroids, and the measurement of subtle dynamical effects. These can include, most notably, the Yarkovsky thermal recoil force or perturbations due to other asteroids.The Gaia mission has published astrometry with very high accuracy for 14.099 asteroids in the Data Release 2 (DR2), and about 10 times more are coming in DR3 (end 2021). The level of accuracy of Gaia is unprecedented, reaching 1 mas or better for each epoch, but it deserves unprecedented care to be exploited. In particular, most archival data (astrometry available at the Minor Planet Center) are the result of a calibration with respect to pre-Gaia catalogues, that are often affected by local systematic errors. Such errors have different possible sources. They can be the result of the tiling of the celestial sphere by a imaging device, whose field of view presents some residual distortion in its astrometric reduction. There can also be effects related to the coupling of two different catalogs, distant in time, used to derive proper motions. Eventually, the adopted reference frame can also introduce other effects.As it has been documented several times in literature such systematic bias, that can vary on spatial scales of a few degrees or less, can also be function of other parameters, such as the magnitude range considered (different bias affect stars of different brightness). To take into account these effects and apply the required corrections, we developed a completely new bias correction computation around on the position of single asteroid observations, instead of the classical approach of computing corrections on fixed grid for each catalogue. Despite being much more time-consuming, our approach allows us to reach a full flexibility on effects related to the field of view size of single surveys, magnitude limit and also epoch-dependent variations. We also implement corrections to the reference frame rotation detected for bright stars (V
A comprehensive catalogue of solar wind properties and events in the inner heliosphere
Authors: Bailey Rachel , Reiss Martin , Möstl Christian , Amerstorfer Ute , Simon Wedlund Cyril , Amerstorfer Tanja , Weiss Andreas , Hinterreiter Jürgen , Guo Jingnan , von Forstner Johan , Barnes David , Davies Jackie , Harrison Richard
Published: October 2020

The evolving ambient solar wind is one of the key links between the Sun and planetary bodies in our solar system. Here we present a comprehensive catalogue of solar wind properties, stream interaction regions, and coronal mass ejections at different locations in the inner heliosphere. Our database incorporates observational data products and also solar wind modelling results. The solar wind modelling is based on two different approaches for modelling the conditions in the ambient solar wind. While the WSA/THUX model combination solves the viscous form of the underlying Burgers equation to compute the two-dimensional solar wind conditions in our solar system, the second approach is a computationally fast machine learning method for predicting the ambient solar wind flows at Earth. Statistics of the ambient solar wind model results for more than 15 years in combination with a catalogue of coronal mass ejections observed at the Earth, Mars and STEREO satellites along with stream interaction regions provide a comprehensive overview of the past and present solar wind behaviour for shaping planetary space weather.
ICAPS Sounding Rocket - Particle Growth
Authors: Schubert Ben , Blum Jürgen , Molinski Noah , Vedernikov Andrei , Balapanov Daniyar , von Borstel Ingo , Rüffert Luca , Aktas Coskun , Schräpler Rainer , Westermeier Moritz
Published: October 2020

The study of dust agglomeration has been a prevalent subject in laboratory astrophysics since its inception. It aims to bridge the gaps in our understanding of early planet formation and helps us interpret the data we receive from telescopes like ALMA, which observe protoplanetary disks.As a contribution to this field, the ICAPS experiment (Interactions in Cosmic and Atmospheric Particle Systems) studies the agglomeration of micrometer-sized, monomeric silica grains under microgravitational conditions. To achieve stable microgravity, the experiment flew onboard the Texus 56 sounding rocket, continuously monitoring and controlling the movement of the dust cloud inside the vacuum chamber. For this, ICAPS employed and tested a novel approach, the thermal trap. It consists of four rings that are fitted with heating elements to keep the cloud centered using thermophoresis. The data from two overview cameras with perpendicular fields of view is used as a reference for the thermal trap. An exemplary image of the cloud can be found on the left hand side of the below figure. The right hand side shows an agglomerate as seen by the on-board long distance microscope and captured by a high speed camera.However, the main focus of this session lies on the scientific results. Within the first two minutes, the silica grains grew to agglomerates of around 103-104 constituent particles via hit-and-stick collisions. The analysis revealed insight into their collision speed, rate of growth and fractal dimension. Also, the influence of their charge could be studied because at several stages of the experiment an electric field was applied. In particular, it was possible to reconstruct some particles in three dimensions by linear displacement through the focal plane of the long distance microscope using the thermal trap. With these findings, it will be possible to classify the growth processes at play. 
Temperature dependent mid-infrared (5-25 μm) reflectance spectroscopy of carbonaceous meteorites and minerals: implication for remote sensing in Solar System exploration.
Authors: Poggiali Giovanni , Brucato John Robert , Dotto Elisabetta , Ieva Simone , Barucci Maria Antonietta , Pajola Maurizio , Fornaro Teresa , Corazzi Maria Angela , Meneghin Andrea , Paglialunga Daniele
Published: October 2020

Interpretation of spectroscopic data from remote sensing strongly depends on the spectroscopic properties, particle size and temperature of materials on the observed surface. Spectral indices of silicates, carbonates, sulfates, oxides and chemicals available on public database are commonly obtained at room temperature and pressure. Whether temperature can affect spectral properties of minerals such as the peak position, band area and shape, was advanced decades ago (Singer & Roush, 1985), but a systematic laboratory study on such effects is still missing. Hitherto, few studies were performed analyzing the effects of space environment, such as low pressure and temperature, on spectroscopic features of minerals, mostly focusing on near infrared spectral region (Moroz, et al. 2000; Hinrichs & Lucey 2002; De Angelis, et al. 2019). This is especially lacking in the mid-infrared region, where laboratory data are almost completely absent. Thus, it is pivotal to acquire spectra in vacuum at various temperatures and varying the particle sizes, for better simulating space environmental conditions.Our apparatus at INAF-Astrophysical Observatory of Arcetri allows reflectance measurements in an extended spectral range from VIS to far IR and at temperatures ranging from 64 K to 500 K. We present here a detailed analysis on temperature-dependent variation on mineral and carbonaceous chondrite samples in the spectral range 1500-400 cm-1 (6.6-25 µm in wavelength). Mineral phases and meteorites analyzed are: pyroxene, olivine, serpentine, Tagish Lake (CI2-ungruped), Aguas Zarcas (CM2) and Orgueil (CI1). Samples are prepared with particle sizes
The Role of Lithology in Silicate Weathering and CO2 Regulation on Rocky Exoplanets
Authors: Hakim Kaustubh , Bower Dan J. , Tian Meng , Deitrick Russell , Auclair-Desrotour Pierre , Kitzmann Daniel , Dorn Caroline , Mezger Klaus , Heng Kevin
Published: October 2020

In the decade of JWST, ELT, TMT, PLATO, ARIEL and other specialized telescopes, observations of carbon dioxide in terrestrial exoplanet atmospheres are possible. The amount of carbon dioxide in the atmosphere of a tectonically active planet such as Earth is regulated by the carbonate-silicate cycle (long-term carbon cycle). Silicate weathering provides essential negative feedback to maintain temperate climates on Earth over billions of years. In this study, we model the chemistry of rock-water interaction for different silicate rocks and minerals applicable to both continental and seafloor weathering. We find that weathering rates depend mainly on the partial pressure of carbon dioxide, surface temperature and lithology, and other factors are secondary. This approach allows possessing a theoretical method to determine both continental and seafloor weathering rates on temperate exoplanets that depend little on present-day Earth calibrations. Our study gives a strong control over the connection between atmospheric observables and the carbon cycle. The ultimate goal is to provide an abiotic library of geological false positives of biosignatures.
Ice lines and the formation of Uranus and Neptune
Authors: Mousis Olivier , Aguichine Artyom , Helled Ravit , Irwin Patrick , Lunine Jonathan I.
Published: October 2020

We aim at investigating whether the chemical composition of the outer region of the protosolar nebula can be consistent with current estimates of the elemental abundances in the ice giants. To do so, we use a self-consistent evolutionary disc and transport model to investigate the time and radial distributions of H2O, CO, N2, and H2S, i.e., the main O-, C-, N, and S-bearing volatiles in the outer disc. We show that it is impossible to accrete a mixture composed of gas and solids from the disc with a C/H ratio presenting enrichments comparable to the measurements (70 times protosolar). We also find that the C/N and C/S ratios measured in Uranus and Neptune are compatible with those acquired by building blocks agglomerated from grains and pebbles condensed in the vicinities of N2 and CO ice lines in the nebula. In contrast, the presence of protosolar C/N and C/S ratios in Uranus and Neptune would imply that their building blocks agglomerated from particles condensed at higher heliocentric distances. Our study demonstrates the importance of measuring the elemental abundances in the ice giant atmospheres, as they can be used to trace the planetary formation location and/or the chemical and physical conditions of the protosolar nebula. 
Classification of fine structures of Saturn kilometric radiation
Authors: Fischer Georg , Taubenschuss Ulrich , Pisa David
Published: October 2020

Saturn kilometric radiation (SKR) is thought to be created by the cyclotron maser instability along auroral magnetic field lines, where radio emissions are generated near the electron cyclotron frequency at the source. Using the Wideband Receiver (WBR) of the Cassini Radio and Plasma Wave Science (RPWS) instrument it was possible to create dynamic spectra of high temporal and spectral resolution. They display the radio wave intensity as a function of time and frequency with a temporal resolution of a fraction of a second and a spectral resolution of ~0.1 kHz. In these dynamic spectra one can find a plethora of various fine structures which we classify in the following way: We first simply distinguish between 0-dimensional structures (dots), 1-dimensional structures (lines), and 2-dimensional structures (areas). For areas we require a minimum extension of 5 seconds in time and 5 kHz in frequency. Our main focus is on the lines, where we again distinguish between the four classes of horizontal lines, vertical lines, and lines with a positive or a negative slope (going to higher or lower frequencies). For the latter two it is thought that they are related to downward or upward moving radiation sources, i.e. bunches of energetic electrons moving down or up along the magnetic field lines. Using these simple 6 classes (DOTS, HORZ, VERT, POSS, NEGS, AREA) it is already possible to classify about 80% of all spectra showing SKR. Unclassified spectra contain no clear linear elements and mostly consist of patchy structures with holes that do not fulfill the minimum size requirement (5 s, 5 kHz) to be classified as areas. Linear elements appear in about one third of the spectra in the frequency range from 100 kHz to 1 MHz. Some spectra can of course be mixed and show dots, lines and areas, but in our classification we prioritize lines over areas and dots. 
Surface energy of the Titan aerosol analog "tholin": implications on cloud formation and aerosol-lake interactions
Authors: Yu Xinting , Hörst Sarah , He Chao , McGuiggan Patricia , Kristiansen Kai , Zhang Xi , Yu Yue , Li Jialin , Garver Julia
Published: October 2020

The photochemical haze produced in the atmosphere of Titan plays a key role in various processes happening on Titan (Hörst, 2017). One of the physical properties of the haze, the surface energy, is crucial for understanding the growth of the solid haze particles and can be used to predict their interactions with solid and liquid species in Titan’s atmosphere and lakes. However, the surface energy of Titan’s haze is not well understood. We produced Titan analog haze materials, so-called "tholin", with different energy sources and measured their surface energies through contact angle and direct force measurements (Yu X. et al., 2020, in revision). From the contact angle measurement, we found that the tholins produced by cold plasma and UV irradiation have similar total surface energy. The commonly used two-liquid component method yields a total surface energy of tholin of ∼65–70 mJ/m. The direct force measurement yields a total surface energy of ∼66 mJ/m2 for plasma tholin. The surface energy of tholin is relatively high compared to common polymers, indicating its high cohesiveness. Thus the Titan haze particles are likely to coagulate easily to form bigger particles, while the surface sand could be hard to be mobilized by the wind because of the high interparticle cohesion. The high surface energy of tholins also makes them good cloud condensation nuclei (CCN) for most hydrocarbon and nitriles condensates in Titan’s atmosphere (Yu Y. et al., in prep), which agrees well with Cassini observations of ice clouds (Anderson et al., 2018). Meanwhile, because of the low contact angle predicted between tholins and Titan’s lake end member species, it is unlikely to form a layer of floating aerosols on the surface of Titan’s lakes.
Consistently Simulating a Wide Range of Atmospheric Scenarios for K2-18b with a Flexible Radiative Transfer Module
Authors: Scheucher Markus , Wunderlich Fabian , Grenfell John Lee , Rauer Heike
Published: October 2020

The atmospheres of small, potentially rocky exoplanets are expected to cover a diverse range in composition and mass. Studying such objects therefore requires flexible and wide-ranging modeling capabilities. We present here our newly developed, flexible radiative transfer module, REDFOX, validated for the Solar system planets Earth, Venus and Mars, as well as steam atmospheres. REDFOX is a k-distribution model using the correlated-k approach with random overlap method for the calculation of opacities used in the δ-two-stream approximation for radiative transfer. Opacity contributions from Rayleigh scattering, UV / visible cross sections and continua can be added selectively.With the improved capabilities of our new model, we calculate various atmospheric scenarios for K2-18b, a super-Earth / sub-Neptune with ∼8 M⊕ orbiting in the temperate zone around an M-star, with recently observed H2O spectral features in the infrared. We model Earth-like, Venus-like, as well as H2-He primary atmospheres of different Solar metallicity and show resulting climates and spectral characteristics, compared to observed data. Our results suggest that K2-18b has an H2-He atmosphere with limited amounts of H2O and CH4. Results do not support the possibility of K2-18b having a water reservoir directly exposed to the atmosphere, which would reduce atmospheric scale heights, hence too the amplitudes of spectral features inconsistent with the observations. We also performed tests for H2-He atmospheres up to 50 times Solar metallicity, all compatible with the observations.
Twinkle: a low-Earth orbit, visible and infrared observatory for exoplanet and solar system spectroscopy
Authors: Edwards Billy , Tessenyi Marcell , Tinetti Giovanna , Savini Giorgio , Stotesbury Ian , Archer Richard , Wilcock Ben , Joshua Max , Windred Philip , Tennyson Jonathan
Published: October 2020

The Twinkle Space Mission is a space-based observatory that has been conceived to measure the atmospheric composition of exoplanets, stars and solar system objects. The satellite is based on a high-heritage platform and will carry a 0.45 m telescope with a visible and infrared spectrograph providing simultaneous wavelength coverage from 0.5 - 4.5 μm. The spacecraft will be launched into a Sun-synchronous low-Earth polar orbit and will operate in this highly stable thermal environment for a baseline lifetime of seven years.Twinkle will have the capability to provide high-quality infrared spectroscopic characterisation of the atmospheres of hundreds of bright exoplanets, covering a wide range of planetary types. It will also be capable of providing phase curves for hot, short-period planets around bright stars targets and of providing ultra-precise photometric light curves to accurately constrain orbital parameters, including ephemerides and TTVs/TDVs present in multi-planet systems.Twinkle is available for researchers around the globe in two ways:1) joining its collaborative multi-year survey programme, which will observe hundreds of exoplanets and solar system objects; and2) accessing dedicated telescope time on the spacecraft, which they can schedule for any combination of science cases.I will present an overview of Twinkle’s capabilities and discuss some example exoplanet surveys to highlight the broad range of targets the mission could observe, demonstrating the huge scientific potential of the spacecraft.
Revisiting migration in a disc cavity to explain the high eccentricities of warm Jupiters
Authors: Debras Florian , Baruteau Clément , Donati Jean-François
Published: October 2020

The distribution of eccentricities of warm giant exoplanets is commonly explained through planet--planet interactions, although no physically sound argument favours the ubiquity of such interactions. No simple, generic explanation has been put forward to explain the high mean eccentricity of these planets.In this talk, I will present a simple, plausible explanation to account for the eccentricities of warm Jupiters: migration inside a cavity in the protoplanetary disc. Such a scenario allows to excite the outer eccentric resonances, a working mechanism for higher mass planets, leading to a growth in the eccentricity while preventing the drag from non-corotating eccentric gas to damp eccentricity. This idea is tested with diverse numerical simulations, which show that the eccentricity of a Jupiter-mass planet around a Sun-like star can increase up and settle to $\sim 0.4$, a value never reached before with solely planet--disc interactions. This high eccentricity is comparable to, if not larger than, the median eccentricity of warm Saturn- to Jupiter-mass exoplanets.I will finally discuss the effects such a scenario would have on observations, notably on the discs lifetime and the physics of inner disc dispersal.
The chemical composition of impact craters on Titan
Authors: Solomonidou Anezina , Neish Catherine , Coustenis Athena , Malaska Michael , Le Gall Alice , Lopes Rosaly , Werynski Alyssa , Lawrence Kenneth , Altobelli Nicolas , Witasse Olivier , Schoenfeld Ashley , Matsoukas Christos , Baziotis Ioannis , Drossart Pierre
Published: October 2020

We investigate the spectral behavior of nine Titan impact craters in order to constrain their surface composition using Visual and Infrared Mapping Spectrometer (VIMS) data and a radiative transfer code (RT) [e.g. 1] in addition to emissivity data. Past studies have looked at the chemical composition of impact craters either by using qualitative comparisons between craters [e.g. 2;3] or by combining all craters into a single unit [4], rather than separating them by geographic location or degradation state. Here, we use a radiative transfer model to first estimate the atmospheric contribution to the data, then extract the surface albedos of the impact crater subunits, and finally constrain their surface composition by using a library of candidate Titan materials. Following the general characterization of the impact craters, we study two impact crater subunits, the ‘crater floor’ and the ‘ejecta blanket’. The results show that Titan’s mid-latitude plain craters: Afekan, Soi, and Forseti, in addition to Sinlap and Menrva are enriched in an OH-bearing constituent (likely water-ice) in an organic based mixture, while the equatorial dune craters: Selk, Ksa, Guabonito, and Santorini, appear to be purely composed of organic material (mainly unknown dune dark material). This follows the pattern seen in [4], where midlatitude alluvial fans, undifferentiated plains, and labyrinths have surface spectra consistent with a mixture of tholin-like spectral features and water ice-like spectral features, while the equatorial undifferentiated plains, hummocky terrains, dunes, and variable plains appear to have spectra similar to a dark material and tholin-like mixture in their very top layers. These observations also agree with the evolution scenario proposed by [3] wherein the impact cratering process produces a mixture of organic material and water-ice, which is later “cleaned” through fluvial erosion in the midlatitude plains. This cleaning process does not appear to operate in the equatorial dunes, which seem to be quickly covered by a thin layer of sand sediment (with the exception of the freshest crater on Titan, Sinlap). Thus, it appears that active processes are working to shape the surface of Titan, and it remains a dynamic world in the present day.[1] Hirtzig, M., et al. (2013). Icarus, 226, 470–486; [2] Neish, C.D., et al. (2015), Geophys. Res. Lett. 42, 3746–3754; [3] Werynski, A., et al. (2019), Icarus, 321, 508-521; [4] Solomonidou, A., et al. (2018), J. Geophys. Res, 123, 2, 489-507
Nadir retrieval of ice clouds, dust and ozone from NOMAD/UVIS on board Exomars TGO
Authors: Willame Yannick , Vandaele Ann C. , Piccialli Arianna , Depiesse Cédric , Daerden Frank , Thomas Ian R. , Ristic Bojan , Wolff Michael J. , Mason Jon , Patel Manish R. , Bellucci Giancarlo , Lopez-Moreno Jose-Juan
Published: October 2020

The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere using a suite of three spectrometers operating in the UV-visible and infrared. NOMAD is a spectrometer operating in ultraviolet (UV), visible and infrared (IR) wavelengths covering large parts of the 0.2-4.3 µm spectral range [1].

The UV-visible “UVIS” instrument covers the spectral range from 200 to 650 nm and can perform solar occultation, nadir and limb observations [2]. The main purpose of UVIS is dedicated to the analysis and monitoring of ozone and aerosols such as dust and ice clouds.  In the present work we will present preliminary results of UV retrievals recorded in nadir geometry: spatial and seasonal distribution of ice clouds, dust and ozone.
Pyrite-induced uv-photocatalytic abiotic nitrogen fixation: implications for early atmospheres and Life
Authors: Mateo-Marti Eva , Galvez-Martinez Santos , Gil-Lozano Carolina , Zorzano Maria-Paz
Published: October 2020

Pyrite-induced uv-photocatalytic abiotic nitrogen fixation: implications for early atmospheres and Life  1Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain.2Department of Computer Science, Electrical and Space Engineering, Luleå Universit of Technology, Luleå, Sweden.  Nitrogen is an essential element for life, a prerequisite for the origin and evolution of life on Earth, or in any other potentially habitable planet. The molecular form of nitrogen, N2, is universally available but is biochemically inaccessible for life due to the strength of its triple bond. Prior to the emergence of life, there must have been an abiotic process that could fix nitrogen in a biochemically usable form. The UV photo-catalytic effects of minerals such as pyrite on nitrogen fixation have to date been overlooked. Here we show experimentally, using X-ray photoemission and infrared spectroscopies that, under a standard earth atmosphere containing nitrogen and water vapour at Earth or Martian pressures, nitrogen is fixed to pyrite as ammonium iron sulfate after merely two hours of exposure to 2,3 W/m2 of ultraviolet irradiance in the 200–400 nm range [1]. Our experiments show that this process exists also in the absence of UV, although about 50 times slower. The experiments also show that carbonates species are fixed on pyrite surface [Figure 1]. We conclude that UV photocatalysis on pyrite may have been a natural mechanism of prebiotic fixation of nitrogen into ammonium sulfates which is then easily released upon contact with liquid water. This property of pyrite may have been incorporated naturally in the prebiotic chemistry evolution, leading to the inclusion of pyrite nano-clusters as reaction centres to generate ammonia from nitrogen, and then from ammonia to generate ammonium sulfates salts in the presence of oxygen. This process has furthermore implication for the abiotic nitrogen fixation on other planetary environments, and it has critical implications for the habitability of planet and the origin of life. Fig. 1    Picture of the Planetary Atmosphere and Surfaces Chamber and XPS spectra of the presence of ammonium sulfate on pyrite surface (on the left). Schematic representation of the processes that lead nitrogen fixation on pyrite surface (on the right), (i) by UV photo-catalysis under low pressure conditions (on the top) and, (ii) by the catalytic effect of iron oxide-iron sulfide tandem under visible light conditions and standard earth atmosphere (on the bottom).        [1]   E. Mateo-Marti, S. Galvez-Martinez, C. Gil-Lozano and M-P. Zorzano, Scientific Reports, 9, 15311 (2019)
Source regions for meteorite falls
Authors: Granvik Mikael , Brown Peter
Published: October 2020

Over the past decade there has been a large increase in the number of automated camera networks that monitor the sky for fireballs. One of the goals of these networks is to provide the necessary information for linking meteorites to their pre-impact, heliocentric orbits and ultimately to their source regions in the solar system. We re-computed heliocentric orbits for the 25 meteorite falls published in or before 2016 from original data sources (Granvik and Brown 2018). Using these orbits, we constrained their most likely escape routes from the main asteroid belt and the cometary region by utilizing a state-of-the-art orbit model of the near-Earth-object population (Granvik et al. 2016), which includes a size-dependence in delivery efficiency. While we find that the general results for escape routes are comparable to previous work, the role of trajectory measurement uncertainty in escape-route identification is explored for the first time. Moreover, the improved size-dependent delivery model substantially changes likely escape routes for several meteorite falls, most notably Tagish Lake which seems unlikely to have originated in the outer main belt as previously suggested. In addition, we find that reducing the uncertainty of fireball velocity measurements below about 0.1 km/s does not lead to reduced uncertainties in the identification of their escape routes from the asteroid belt and, further, their ultimate source regions. The analysis suggests that camera networks should be optimized for the largest possible number of meteorite recoveries with measured speed precisions of order 0.1 km/s. We will present updated results based on a new NEO model (Granvik et al. 2018) and complement our data set with the falls that have been reported since 2016.References: Granvik, M. and Brown, P. (2018). "Identification of meteorite source regions in the Solar System", Icarus 311, 271-287. Granvik, M., Morbidelli, A., Jedicke, R., Bolin, B., Bottke, W. F., Beshore, E., Vokrouhlicky, D., Delbo, M., Michel, P. (2016). "Super-catastrophic disruption of asteroids at small perihelion distances", Nature 530, 303-306.Granvik, M., Morbidelli, A., Jedicke, R., Bolin, B., Bottke, W. F., Beshore, E., Vokrouhlicky, D., Nesvorny, D., Michel, P. (2018). "Debiased orbit and absolute-magnitude distributions for near-Earth objects", Icarus 312, 181-207.