Abstracts

There is a total of 20 abstracts.

1) The rarity of very red TNOs in the scattered disk and high order resonances

Mohamad Ali-Dib - NYU (Postdoc)

Talk

We investigate the origins of the photometrically Very Red and Less Red Trans-Neptunian Objects. We first reanalyse the dataset of Marsset et al. (2019) and find that, in addition to the known color- inclination correlation in hot TNOs, a similar trend exists for color-eccentricity.We show that VR TNOs are dynamically sharply constrained to eccentricities < 0.42 and inclinations < 21 deg, leading to a paucity of VR scattered disk and distant MMR objects.We then interpret …

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2) Coupling the Atmospheric and Dynamical Evolution of Close-in Exoplanets

Omar Attia - University of Geneva (PhD student)

Talk

The vast majority of the detected exoplanets orbit in less than a month around their star, in extreme conditions unmet in the Solar System. The demographics of these close-in planets exhibit a striking feature: the lack of Neptune-size worlds on very short orbits, also dubbed the ‘Neptunian desert’, which challenges our understanding of planetary formation and evolution. Two classes of mechanisms thought to play a predominant role in shaping the desert are orbital migration, which brings …

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3) Simuler l'intéraction entre un vent solaire turbulent et différents corps du système solaire

Etienne Behar - Laboratoire Lagrange, Observatoire de la Cote d'Azur (Postdoc)

Talk

La simulation auto-cohérente de l'interaction entre un vent solaire turbulent et différents corps du système solaire est rendue possible grace à un nouveau solveur hybrid-PIC multi-GPU et une approche spécifique en deux étapes. Ce nouveau type de simulation et ses premiers résultats sont ici présentés, en utilisant l'exemple d'une comète de moyenne activité. Cette première application démontre le potentiel de cette approche pour aller au-delà de l'hypothèse classique d'un vent laminaire en amont de l'obstacle. …

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4) New observations and modeling studies of Pluto’s atmosphere and ices.

Tanguy Bertrand - LESIA (Senior scientist)

Talk

The flyby of Pluto in 2015 by New Horizons revealed that Pluto is one of the most active solid bodies in the Solar System, with a wide array of processes on display, including ongoing tectonism, cryovolcanism, solid-state convection, glacial flow, atmospheric circulation, surface-atmosphere volatile exchange, aeolian processes, atmospheric photochemistry, microphysics, and haze and cloud formation.
Six years after New Horizons flyby, we will quickly review what remain the main enigmas regarding its climatic activity. …

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5) Preuve morphométrique de dépressions festonnées sur la comète 67P.

Axel BOUQUETY - LAM/CNRS (Postdoc)

Talk

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Au cours d'une précédente étude, nous avons étudié deux dépressions situés dans la région de Ash, à la surface de la comète 67P. L'approche morphométrique comparative a permis de mettre en évidence que les deux dépressions ont grandi de plusieurs mètres avec le dernier passage au périhélie. Nous avons observé que cette croissance n'est pas forcement lié à une érosion de falaise, ainsi il est possible de suggérer que la sublimation de la glace joue …

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6) Premières mesures directes des vents stratosphériques de Jupiter et de Saturne avec ALMA

Thibault Cavalie - Laboratoire d'Astrophysique de Bordeaux (Chargé de Recherche)

Talk

Les vents zonaux dans la haute troposphère de Jupiter et de Saturne ont été mesurés depuis des décennies grâce à la technique du cloud-tracking. Ces vents alternent entre des vents progrades et rétrogrades et peuvent atteindre des vitesses de ~150 m/s sur Jupiter et ~400 m/s sur Saturne, à l'équateur. Juno et Cassini ont montré que ces vents s'étendent aux couches profondes troposphériques. Dans les zones aurorales de Jupiter, des vents ionosphériques ont également été …

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7) Que pourra-t-on observer avec les sondes électriques de la future mission Dragonfly vers Titan ?

Audrey Chatain - Sorbonne Université / LMD (Postdoc)

Talk

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Titan, la plus grande lune de Saturne, est l'endroit du Système Solaire possédant les paysages les plus ressemblants à la Terre. Son épaisse atmosphère et les températures glaciales qui y règnent permettent au méthane d'avoir un cycle hydrologique semblable à l'eau sur Terre. Titan a aussi comme particularité de posséder une brume orange épaisse couvrant toute la lune, ainsi qu'un océan d'eau liquide sous-terrain.

La future mission de la NASA, Dragonfly, va partir …

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8) Comment les gaz transparents affectent-ils le déclenchement de l’emballement de l’effet de serre ? Éclairages à partir de différents modèles radiatifs-convectifs 1D.

Guillaume CHaverot - Observatory of Geneva (PhD student)

Talk

Guillaume Chaverot, Emeline Bolmont et Martin Turbet

Il est intéressant d’étudier l’emballement de l’effet de serre de la vapeur d’eau [1-4] afin de mieux déterminer l’insolation seuil de cet effet catastrophique, et par conséquent le bord interne de la Zone Habitable (ZH). Certaines études [5-7] ont montré que le déclenchement de l’emballement de l’effet de serre peut être retardé en raison d'une augmentation de l’émission thermique (OLR = Outgoing Longwave Radiation) par l'ajout de gaz …

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9) Water formation in oxidized atmospheres of terrestrial exoplanets

Thomas Drant - UVSQ / LATMOS (Student)

Talk

The James Webb Space Telescope which will be launched in October 2021 might provide for the first time accurate atmospheric signatures for terrestrial exoplanets. However, the atmospheric chemistry of these exoplanets remains largely unexplored despite its importance for the understanding of future observations. The present study focuses on oxidized CO2-dominated atmospheres with an important mixing ratio of molecular hydrogen. Laboratory experiments with a plasma reactor were conducted to study the photochemistry of this particular system. The …

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10) A new generation of statistical methods for exoplanet detection with radial velocity

Nathan Hara - Université de Genève (CHEOPS Fellow)

Talk

Radial velocities are essential to estimate the mass of exoplanet, and have the potential to detect Earth-like planets around Sun-like stars. However, radial velocity data are corrupted by instrumental systematics and complex stellar noises, which currently inhibit the detection of Earth analogs. In this presentation, we will review some of the latest radial velocity data analysis tools and show that their application has a significant impact on the scientific potential of radial velocities. More precisely, …

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11) A new type of cloud discovered from Earth in the upper Martian atmosphere

Jean Lilensten - CNRS - IPAG (Senior scientist)

Talk

During the 2020 Mars opposition, we observe from Earth the occurrence of a non-typical large-scale high-altitude clouds system, extending over thousands of km from the equator to 50°S. Over 3 hours, they emerge from the night side at an altitude of 90 (-15/+30) km and progressively dissipate in the dayside. They occur at a solar longitude of 316°, west of the magnetic anomaly and concomitantly to a regional dust storm. Despite their high altitude, …

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12) The dissipation of tides in stars hosting planets: towards a complete picture along their evolution

Stephane Mathis - Département d'Astrophysique CEA/IRFU - AIM (CEA Astrophysicist)

Talk

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S. Mathis, J. Ahuir, A. Astoul, L. Amard, E. Bolmont, C. Charbonnel, C. Baruteau, F. Gallet

The on-going space missions TESS and CHEOPS coupled with ground based high precision instruments like SPIRou are opening a new window for our understanding of the evolution of short-period planets orbiting low-mass stars (M- to F-types) along their structural, rotational, and magnetic evolutions. In this context, an important objective is to understand the observed orbital architectures and rotation (including the stellar spin-orbit inclination) of the host …

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13) Dust grains shattering in protoplanetary discs: collisional fragmentation or rotational disruption ?

Stéphane Michoulier - Centre de Recherche Astrophysique de Lyon (PhD student)

Talk

    In the theory of planetary formation, growth of sub-µm to mm dust aggregates in protoplanetary discs into planetesimals is hampered by theoretical problems commonly known as the radial drift barrier and the fragmentation barrier, preventing dust grains to survive and form lately planets within discs.
A solution to overcome these barriers is to consider grains porosity which allows dust to grow faster and longer while being less sensitive to fragmentation than compact grains (Garcia & …

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14) Preparing the interpretation of the WISDOM/ExoMars2022 radar soundings

Nicolas Oudart - LATMOS (PhD student)

Talk

WISDOM (Water Ice and Subsurface Deposits Observation on Mars) is the Ground Penetrating Radar of the ExoMars 2022 rover, Rosalind Franklin. This rover being the very first able to collect samples down to 2 m in the Martian subsurface, information on the subsurface structure and composition is required prior to any drilling operation, to select an interesting underground target and avoid hazards for the drill. To perform this study of the shallow subsurface properties, the …

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15) An atmospheric origin for HCN-derived polymers on Titan

zoe perrin - LATMOS (PhD student)

Talk


Titan’s haze is strongly suspected to be an HCN-derived polymer, but despite the first in-situ measurements by the ESA-Huygens space probe, its chemical composition and formation process remain largely unknown. To investigate this question, we simulated the atmospheric haze formation process experimentally. We synthesized analogues of Titan’s haze, named Titan tholins, in an irradiated N2 - CHgas mixture mimicking Titan’s upper atmosphere chemistry. HCN was monitored in-situ in the gas phase simultaneously …

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16) Stability and spacing of tightly packed systems

Antoine Petit - Lund University (Postdoctorant)

Talk

Exoplanet transit surveys have revealed the existence of numerous multi-planetary systems packed close to their stability limit.  This feature likely emerges from the formation and dynamical history of the system. Understanding it in detail is thus key to constrain our planet formation scenarios. While the stability limit has been known empirically for decades, no theoretical explanation was proposed yet. I present a mechanism driving the instability of tightly packed system. Based on the chaotic diffusion …

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17) The NAROO digitization center

Vincent Robert - IMCCE - Paris Observatory / IPSA (Teacher-Researcher)

Talk

The New Astrometric Reduction of Old Observations NAROO center is built at Paris Observatory, Meudon, and is dedicated to the measurement of astro-photographic plates and the analysis of old observations. The NAROO digitizer consists of a granite based Newport-Microcontrol open frame air-bearing XY positioning table, a scientific sCMOS camera, and a telecentric optical system. The plate holder assembly is suited for mounting glass plates up to 350-mm square. The machine positioning stability is better than …

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18) L'obliquité de Saturne expliquée par l'expansion orbitale de Titan

Melaine Saillenfest - IMCCE, Observatoire de Paris (Chargé de recherche)

Talk

L'inclinaison importante de l'axe de rotation de Saturne (27°) comparée à celle de Jupiter (3°) nécessite une explication dynamique. Pendant des années, les astronomes pensaient que Saturne s'était inclinée pendant la migration planétaire tardive, il y a plus de quatre milliards d'années, par le biais d'une résonance spin-orbit séculaire. Des études récentes montrent que ce scénario traditionnel est en contradiction avec l'expansion orbitale de Titan, la plus grosse lune de Saturne, dont la vitesse a …

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19) Pourquoi et comment les nuages empêchent la formation d'océans d'eau liquide sur les planètes telluriques primitives

Martin Turbet - Observatoire Astronomique de l'Université de Genève (Postdoc)

Talk

Dans cette contribution, je présenterai les résultats de nouvelles simulations numériques 3-D de l'atmosphère de planètes primitives (supposément riches en vapeur d'eau) réalisées avec le Modèle de Climat Global (GCM) "générique" du LMD. Je montrerai d'abord comment et pourquoi les nuages tendent à s'accumuler préférentiellement sur la face nocturne de ces planètes, dès que la vapeur d'eau est un composé majoritaire de l'atmosphère. Puis, je montrerai comment et pourquoi ce résultat a des conséquences majeures …

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20) The role of cohesion in small body evolution: from 'Oumuamua to Bennu

Yun Zhang - Laboratoire Lagrange/CNRS, Université Côte d’Azur, Observatoire de la Côte d’Azur (Postdoc)

Talk

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Cohesion is a fundamental property that is significant for understanding observed behaviors of small bodies and making predictions. In effect, whether cohesion is present or not makes a very big difference in the behavior of a small asteroid under various processes, such as YORP spin-up, surface motions, impact cratering, and tidal disruption. Moreover, with the wide diversity of small bodies’ properties (e.g., bulk density, packing configuration, spin rate, shape), the effect of cohesion is very …

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