Séminaires au LESIA

Dynamical interaction between debris disks and planets can induce several features in the disk, such as brightness asymmetries, warps, gaps, and spirals. Detections of such features in high-contrast imaging observations can therefore be used to infer the existence of yet-undetected companions. The edge-on debris disk detected around the young, nearby A0V star HD 110058 shows warped features resembling those seen in the disk of beta Pictoris, which could indicate the presence of a perturbing planetary-mass companion in the system. We investigated new and archival scattered light images of the disk in order to characterise its morphology and spectrum. Our work uses data from two VLT/SPHERE observations and archival data from HST/STIS. We analysed vertical profiles along the length of the disk to extract the centroid spine position and vertical height, and extracted the surface brightness and reflectance spectrum of the disk. We detect the disk between 20 au (with SPHERE) and 150 au (with STIS), at a position angle of 159.6° ± 0.6°. The disk is marginally vertically resolved in scattered light with SPHERE, with a vertical aspect ratio of 9.3 ± 0.7% at 45 au. Analysis of the spine shows an asymmetry between the two sides of the disk, with a 3.4° ± 0.9° warp between 20 au and 60 au. The outer parts of the disk are also asymmetric with a tilt between the two sides, compatible with a disk made of forward-scattering particles and an inclination of <84°. Dynamical models suggest an undetected inner planetary-mass companion on a mutually inclined orbit with the disk could explain the warp.

With FAST, the largest single-dish telescope ever built , we have designed the Commensal Radio Astronomy FAST Survey (CRAFTS), which realizes, for the first time at any major facility, simultaneous data recording of pulsar search, HI imaging, HI galaxies, and transients (FRB and SETI). CRAFTS has discovered 200 pulsars, 10 FRBs including the only persistently active repeater FRB 20190520B, and 5000 d^2 HI images with 1% calibration consistency, 5-10 times better than what is available from Arecibo. Based on CRAFTS, we derived a FRB event rate 120K per day per 4pi. We find universal frequency-dependent depolarization among repeating FRBs, which can be well fitted by multi-path scattering and a single free parameter sigma_RM that described the complexity of the magnetized environments of FRBs. We have published in 2021 the first complete burst rate energy distribution toward any FRB, which is clearly bimodal. Such bimodality was later borne out in the subsequent monitoring of all the active repeaters. Recently, 10% drop of FRB 121102’s DM on a decade time scale, is being robustly detected. I am proposing an evolutionary picture of FRBs, which aims to unify not only repeating FRBs, but most if not all non-repeaters.

The “Extremely Large Telescope” (ELT), currently built by ESO in Chile, will be decisive for unprecedented observations of asteroids, trans-Neptunian objects, and Centaurs as it will offer very high spatial resolution and sensitivity. The MICADO and HARMONI instruments in particular will allow in-depth studies of rocky and icy dwarf planets. They will also bring constrains on the physical properties (size, shape, rotation, density, mass, internal structure) of hundreds of asteroids and about twenty TNOs by imaging and high precision astrometry. Their composition will be mapped by narrowband imaging and integral field spectroscopy. MICADO will be served by MORFEO, a multi-conjugate adaptive optics with several laser stars and several deformable mirrors. The use of MORFEO will be crucial to observe faint and sometimes fast objects against the sky with the best possible resolution. Members of the MORFEO and HARMONI teams, we aim at carrying out the scientific preparation of the instrument by (i) defining strategies for performing the observations of the minor bodies of the Solar System (ii) simulating images and spectra with a complete set of numerical tools and laboratory reflectance data. We will present this approach and the expected performances after a brief description of the MICADO/MORFEO instruments.

China’s planetary exploration mission will be shortly introduced. Some typically planetary radio science results will be reviewed. Then, this report will introduce the Tianwen-2 mission, China’s follow-up mission to the Tianwen-1 Mars exploration. The Tianwen-2 mission focuses on near-earth asteroid and main-belt comet research. Targeting asteroid 2016HO3 and main-belt comet 311P, the report will delve into their characteristics, scientific goals, and exploration strategies. It aims to analyze orbital dynamics, gravitational fields, and material composition, which can unravel the solar system’s formation and evolution. Additionally, the mission’s outline and payload details will be briefly outlined.

In plasma and radio waves sensing, we are now running Plasma Wave Experiment (PWE) aboard Arase spacecraft which are investigating Geospace. This spacecraft have provided continuous observations of the inner magnetosphere, which extension until FY2032 has been approved. With good particle measurements, we are revealing electron and ion waves which can contribute to the acceleration and loss of energetic particles in Geospace.

Associated with this mission, we are also running two major collaborations with Europe including LESIA colleagues. The first is Plasma Wave Investigation (PWI) aboard the Mio spacecraft of BepiColombo, ESA-JAXA joint mission to Mercury, which will observe Mercury on the orbit from the end of 2025. The second is Radio and Plasma Wave Investigations (RPWI) aboard ESA JUpiter ICy moons Explorer (JUICE) mission to Jupiter, which will observe Jovian system on the orbit from 2031. In both Japan and Europe, main players are overlapped and collaborating strongly in both missions and beyond.

In this presentation, we show (1) Recent progress by Arase, (2) recent Mercury flyby studies of BepiColombo/Mio PWI, and (3) recent status of JUICE RPWI, focusing to Lunar-Earth flyby plans in this Aug which is linked to the feasibility studies on Jovian orbit.

The polar atmosphere of Jupiter is a complex region were chemistry, dynamics and magnetospheric-coupling are intertwined. Several decades of ground-based observations and spacecraft measurements (Voyager, Cassini, Juno) are progressively revealing how rich and complex these regions are. Species such as HCN, CO, H2O were brought in large amount during the Shoemaker-Levy 9 impact in 1994 and provide important dynamical tracers, as they have spread across the atmosphere over the last 30 years. Hydrocarbons originate from methane-photolysis and are affected by auroral precipitations, leading to the formation of aerosols across the polar cap. Magnetosphere-ionosphere coupling generates powerful electrojets that drag the neutral stratosphere underneath. I will review our current understanding of these regions, based on observations from Cassini, Juno, ALMA, Gemini, and IRTF.

Volcanism plays a major role in Mercury’s geological processes, and understanding this activity is crucial to delimit the evolution of the planet. The presence of large pyroclastic deposits contrasts with formation models which predict a volatile depleted crust and mantle, especially in the recent past. Constraining the timing of these volcanic eruptions and the extent of the resulting pyroclastic deposits is fundamental to refine our knowledge of Mercury’s internal evolution and improve the formation models. Using a Deep Learning approach with MESSENGER/MASCS spectra we delimit the extent of irregular pyroclastic deposits and update the area of these features. Moreover, we study the evolution of the spectral properties of pyroclastic deposits over time, using the degradation state of the vent as a reference for the deposit age. We observe a trend between the deposit spectra and the vent degradation characterized by a rapid initial darkening and flattening over time followed by stabilization. The oldest deposits reach a steady state with no further spectral changes. To explain these temporal variations in spectral properties, we propose three potential processes : space weathering, mixing with the background and changes in pyroclast size over time. We examine the implications of space weathering on spectral properties and discuss the eruption timeline for each scenario. Finally, we introduce the ongoing lab measurement campaign to study the effect of grain size and composition on the spectral properties of Mercury analogs, with the aim of improving our knowledge of how different processes can affect the spectra of this planet.

Several Solar System bodies target of past, present and future space missions are characterized by dark rocky surfaces and complex mixtures of several component with different grain size regolith material. Space missions with their payloads of scientific instrumentation are our gateway to the knowledge of these surfaces, and in recent years the gap is being further closed with the study of samples returned to Earth. Meanwhile, analyzing analogous materials, like minerals mixtures and meteorites, remains one of the pivotal laboratory investigations to support remote sensing interpretation. It also represents one of the most challenging experiments, in particular when multiple components are used in the mixtures. We will review briefly the state of art of laboratory investigations and present in several results from different works that share the common goal of studying how the complex mixing of different grain size and dark materials can affect the behavior of infrared spectra in the near- to mid-infrared range (1.25-25 μm).

La surface de Mercure est soumise à l’altération spatiale de par l’absence d’atmosphère dense. Le bombardement météoritique, l’irradiation du vent solaire, les températures extrêmes ainsi qu’un volcanisme intense ont fortement modifiés la surface au cours du temps. Les données spectrales obtenues par la mission NASA/MESSENGER ont permis de mieux contrainte l’évolution de la surface de Mercure ; cependant les propriétés spectrales ont grandement été influencées par l’irradiation solaire pouvant induire un biais lors de leur interprétation. Des expériences de laboratoire simulant l’irradiation du vent solaire permettent de contraindre les changements spectraux liés à l’environnement. Une meilleure compréhension du rôle de l’altération spatiale sur les propriétés spectrales est essentielle aux vues de l’arrivée imminente de la sonde ESA/JAXA/BepiColombo.

Mercury’s surface is subject to space weathering due to the absence of a dense atmosphere. Meteorite bombardment, solar wind irradiation, extreme temperatures and intense volcanism have intensely modified the surface over time. The spectral data obtained by the NASA/MESSENGER mission have enabled us to better constrain the evolution of the surface however, the spectral properties have been greatly influenced by solar irradiation, which can lead to a bias in their interpretation. Laboratory experiments simulating solar wind irradiation are used to constrain spectral changes induced by the environment. A better understanding of the role of space weathering on spectral properties is essential in preparation for the imminent arrival of the ESA/JAXA/BepiColombo mission.

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https://us02web.zoom.us/j/89077687967?pwd=RTdEeE9BaUN1ZmRkUUZKUU5HMVdRdz09