Centre de Conférences Jules Janssen

AsteRisk

2026-04-16T00:00:00Z

Organisateur : Daniel Hestroffer (IMCCE)

De par leur proximité, les astéroïdes géocroiseurs sont parmi les petits corps du système solaire des cibles de choix aussi bien pour les observations télescopiques sol que pour les rendez-vous spatiaux (Itokawa, Eros,…) ou encore les missions de retour d'échantillons (Hayabusa, Marco-Polo, Osiris-Rex, …). Comme la durée de vie dynamique de ces objets est assez courte, ils proviennent pour la plupart de réservoirs situés dans la bande principale (d'autres sont des comètes éteintes, etc.). Certains de ces objets géocroiseurs peuvent avoir au cours du siècle à venir des rapprochements serrés avec des planètes, la Lune ou bien la Terre et montrer des risques de collisions. D'une manière générale, la distribution en taille de ces corps est telle que plus ils sont petits, plus ils sont nombreux et plus le risque de ‘collision' est fort. Pour les plus petits de ces corps (diamètre < 10m environ) les conséquences sont bénignes, pour les plus gros de ces corps (diamètre > 1km environ) les conséquences sont catastrophiques au niveau planétaire, mais fort heureusement ces évènements restent extrêmement rares sur des échelles géologiques, enfin pour des tailles intermédiaires (20-200m) on peut s'attendre à des conséquences plus sérieuses au niveau géographique local.

Nous proposons de réunir sur un atelier de prospective et d'échanges inter-disciplinaire différents acteurs de la recherche française qui pourraient apporter des indications sur les recherches à développer dans ce domaine. Avec comme objectif particulier de définir des pistes pour établir un modèle de référence pour l'aide à la décision. La chaîne des objets d'études qui seront abordés au cours de cet atelier englobera les problèmes d'aléas de vulnérabilité et de risques liés aux géocroiseurs. Ceci comprendra la caractérisation orbitale, les incertitudes et propagations d'erreurs, la caractérisation physique, la modélisation des impacts, la prédiction des conséquences pour les personnes et les biens à partir de systèmes d'information géographiques, les moyens d'observations sols et spatiaux, les problèmes de sécurité, les paramètres sociaux et sociétaux, les systèmes d'information et de communication pour les différents interlocuteurs (grand public, médias, tutelles, décideurs).

Ecole doctorale : Simulation Numérique

2026-04-16T00:00:00Z

Organisateur : F. Pantellini, R. Grappin

La simulation numérique est un outil très utilisé en physique des plasmas. Il est en effet compliqué de monter des expériences de laboratoires. L'obtention de l'état plasma nécessite un vide très poussé et les expériences sont lourdes. De plus les phénomènes observés dans l'espace et les conditions rencontrées sont très difficiles à reproduire en laboratoire. Une simulation est une sorte d'expérience numérique : grâce à un code numérique, on résoud les équations qui décrivent la physique du système (équations de Maxwell et équations de la dynamique), on discrétise ces équations (on résoud le problème sur une grille et à des temps discrets), on fixe des conditions aux limites. Sur les résultats de la simulation on réalise un certain nombre de diagnostics qui permettent d'analyser les phénomènes physiques.

La formation est destinée a priori aux doctorants (de toute école doctorale) mais toutes les personnes intéressées sont bienvenues.

Remote Sensing of the Earth from Space

2026-04-16T00:00:00Z

Organisateurs : Filipe Aires, Catherine Prigent (LERMA, tel : 01 40 51 20 18)

The purpose of this course is to provide the basic scientific background to students interested in Earth remote sensing from space and its applications. The students are part of a FP7 network “Greencycle II” dedicated to improve the current understanding of the impacts of climate-biogeochemistry feedbacks on the evolution of the Earth system over the next two centuries. Most students have a solid background in climate modeling but limited experience with satellite data. The objective of this course will be to provide them with the key information to use satellite observations in climate modeling, as inputs, as well as for model evaluations.
The lectures start with the fundamental elements of the basic physics involved in remote sensing. A wide range of applications will be covered, from atmospheric sounding to land and ocean studies. An introduction to the satellite orbitography will be given. Another lecture will present innovative statistical techniques to retrieve geophysical parameters from satellite observations. Numerical works are planed for three days : half a day will focus on the classification and interpretation of real satellite observations at different wavelengths, another one will be dedicated to analysis of satellite data, and the remaining time will concentrate on radiative transfer simulations and inversion of satellite observations.

Workshop ROSETTA – OSIRIS at Lutatia

2026-04-16T00:00:00Z

Organisateur : Antonella Barucci (LESIA, tel : 75 39)

From the ground based observations, 21 Lutetia appeared to be a puzzling asteroid different from all the other asteroids. Its nature was uncertain because of contradictory observations, either favoring an M type or a C type asteroid. From polarimetry, Lutetia appeared an atypical object with a surface covered by a fine-grained regolith.
From the amazing images received by OSIRIS imaging system on board of ESA Rosetta spacecraft, Lutetia reveals a complex and morphologically diverse surface, confirming its “weird” character.

Lutetia seems to be a very old object with an irregular shape which is the result of its collisional history. Some smooth younger areas have been also observed. The asteroid lifelong bombardment produced several big craters (tens of kilometers), and many different generation of smaller craters. An apparently tick regolith layer probably covers most of the surface of the asteroid and its presence is revealed by the unique land slide structures along the wall of some craters, most likely generated by impact-induced seismic activity. Sparsely the presence inside some big craters of sparse boulders, apparently dark, indicates a complex impact mechanism.

Moreover images display a great richness of different structures : pits, craters chains, ridges, scarps and wide younger terrains.

The first analysis of the data shows the extreme diversity of Lutetia which does not resemble any other space explored asteroid. The variety of shapes, morphologies, structures, histories provides us with an invaluable patrimony of information.

Goal of the workshop is to discuss the first analyses of the images taken by OSIRIS instruments (taking into account the synergies with the others Rosetta experiments) and summarize the main results concening both the nature of Lutetia and, in général, the knowledge of the asteroid population.

Astrobiology in the Early Solar System

2026-04-16T00:00:00Z

Organisateurs : John Robert Brucato, Elisabetta Dotto (INAF, Italy) et Antonella Barucci (LESIA)

SCIENTIFIC PROGRAM

Monday 18 April
14:30 - 15:00 Welcome and Opening

Laboratory studies of Solar System materials (chairperson : J.R. Brucato)
15:00 - 15:30 P. Ehrenfreund
"Astrobiology field research in the Utah desert"
15:30 - 16:00 R. Saladino, J.R. Brucato, A. De Sio, G. Botta, E. Pace,
INFN-LNF, L. Gambicorti
"Photochemical Synthesis of Citric Acid Cycle Intermediates
Based on Titanium Dioxide"
16:00 - 16:30 G. Libourel, Marco Delbo, Guillaume Thomas
"Regolith formation on asteroids : an experimental study"
16:30 - 17:00 Coffe Break
17:00 - 17:30 G. Strazzulla
"Ion irradiation effects relevant to Astrobiology"
17:30 - 18:00 R. Brunetto
"Laboratory studies at the "IAS - Astrochimie et Origines" team"
18:00 - 18:30 J. M. Trigo-Rodríguez
"Aqueous alteration in carbonaceous chondrites : is the extent of
hydration and the link between clays and soluble organics
talking us about a prebiotic chemistry ?"
18:30 - welcome glass

Tuesday 19 April
Solar System(s) formation and evolution (chairperson P. Michel)
9:30 - 10:00 F. Marzari
"Dynamics of growing planets"
10:00 - 10:30 H. Rauer
"Extrasolar planets : Putting the Solar System into context"
10:30 - 11:00 P. Michel
"The impact history on Earth and potential consequences for the
delivery of water and organics"
11:00 - 11:30 Coffee Break
Observations (chairperson M. Fulchignoni)
11:30 - 12:00 A.C. Levasseur-Regourd
"Commonalities between cometary nuclei and pristine asteroids :
implications for dust particles impacts during the LHB"
12:00 - 12:30 L.M. Lara
"Equilibrium and disequilibrium chemistry of exoplanetary
atmospheres"
12:30 - 13:00 J.P. Emery
"Searches for organics on outer Main Belt asteroids, Trojan
asteroids, and Kuiper Belt objects"

13:00 - 15:00 Lunch and tour of Meudon

Search for signs of life (chairperson E. Dotto)
15:00 - 15:30 H. Cottin, M. Delbo, G. Thomas
"Toward high resolution mass spectrometry in space for the
search of complex organic molecules"
15:30 - 16:00 S. Branciamore
"Mineral matrices as a cradle of primordial genetic material"
16:00 - 16:30 Coffee Break
16:30 - 17:00 F. Gomez Gomez
"Remote and "in situ" identification of biosigantures in the
search for Life"
17:00 - 17:30 David Cullen
"The Life Marker Chip experiment on ExoMars"
17:30 - 18:00 John Robert Brucato
"Astrobiology with primitive asteroids"
18:00 - 18:30 Frances Westall
"Life in the early Solar System"
18:30 - Cocktail

Wednesday 20 April
MarcoPolo-R (chairperson M.A. Barucci)
10:00 - 11:00 Working Groups and Open Discussion
11:00-11:30 Coffee Break
11:30 - 12:30 Final Considerations and Actions

Astrobiology seeks answers to three basic questions : How does life begin and evolve ? Does
life exist elsewhere in the universe ? What is the future of life on Earth and beyond ? To
attempt to answer these three profound questions, a detailed study of origin and evolution of
our Solar System as well as of the other planetary systems is requested. Precious information
is obtained studying the nature of small bodies population in our Solar System, such as
comets, asteroids and satellites as well as of disks and planets around other stars.
Small bodies of the Solar System, as primitive leftover building blocks of the planetary
formation process, offer clues to the chemical mixture from which the planets formed some
4.6 billion years ago. Abundant within the inner solar system and the main impactors on
terrestrial planets, small bodies may have been the principal contributors of the water and
organic material on Earth. In fact, current exobiological scenarios for the origin of life invoke
an exogenous delivery of organic matter to the early Earth. It has been proposed that primitive
bodies could have brought these complex organic molecules capable of triggering the prebiotic
synthesis of biochemical compounds on the early Earth. Small bodies can therefore be
considered to be equivalent to DNA for unravelling our solar system's history, offering us a
unique window to investigate both the formation of planets and the origin of life. Morevoer,
the study of debris disks around stars, as well as the analysis of extra-solar planets can give us
important hints to understand how our own Solar System is peculiar and how the mechanisms
so far invoked for its formation can be extended to the whole sample of known planetary
system. Thus, it is necessary to investigate how solid planets formed, how they acquired
liquid water, other volatile species and organic compounds, and how processes in planetary
systems and galaxies affected their environments and their habitability. The use of theoretical
and observational studies of the formation and evolution of planetary systems and their
habitable zones is essential to predict where water-dependent life is likely to be found in such
systems.
One of the major achievements in meteoritics over the past 20 years has been in the isolation
and detailed analyses of a wide range of different pre-solar grains found in primitive
meteorites. They have offered insight, which was previously undreamed of, into specific
nucleosynthetic processes and the thermo-physical conditions of the accompanying
circumstellar shells associated with a wide variety of such processes. The latest and
potentially the most important group of grains identified in meteoritic material is the one
composed of interstellar silicates. Next future will offer the opportunity to investigate the
abundance of pre-solar grains accreted in the parent body and to search for new, less robust
grains that have not survived the meteorite formation processes.
The aim of the proposed atelier is therefore to have a heterogeneous scientific community
composed by scientists working on planetary science, chemistry, biology, and astrobiology to
have the status of the art of the present knowledge in the early Solar System and other
planetary systems and to discuss the road map for the next future.
Participants will confront the various issues related to how organic molecules are formed and
evolve in space, how much and what kind of processing occurs as material enters the
primordial solar system, the extent to which small objects preserves the original organic
makeup of interstellar grains, in what way such material has been further processed, whether
comets and asteroids are a good candidate for delivering bulk of Earth's pre-biotic organic
inventory, and what is the extent and complexity of organic chemical evolution in interstellar
versus solar system material.
The tentative list of topical areas in which these issues will be addressed include :
· Astronomical, theoretical, and laboratory investigations to support planning for and
interpretation of data from missions designed to detect and characterize Solar System
objects and extrasolar planets.
· Characterize the exogenous and endogenous sources of matter (organic and inorganic)
in our Solar System and in other planetary and protoplanetary Systems.
· Determine how to recognize signatures of life on other worlds.
· Identify biosignatures that can reveal and characterize past or present life and remotely
measured planetary atmospheres and surfaces.
· Observations of interstellar molecules,
· Analysis of extraterrestrial samples,
· Modeling of chemical/physical processes in cloud/disk/small objects environment.

Water in Asteroids and Meteorites

2026-04-16T00:00:00Z

Organisateurs : Humberto Campins (University of Central Florida, US), Antonella Barucci (LESIA)

The presence and distribution of water in asteroids is relevant to the origin and evolution of these objects, of our Solar System, and even of Earth's own water. Water in asteroids has been detected in the form of hydrated minerals and recently as surface ice. The study of water and hydrated minerals in meteorites is equally exciting and relevant to this topic. A focused workshop that would bring together the astronomical and meteoritic communities would be a rare forum likely to advance significantly this field.
There have been important recent developments in this field. The tantalizing indication of water ice surviving in the Themis asteroid family, as suggested by the cometary activity observed in two asteroids belonging to this family, has been confirmed by the detection of surface ice on asteroid 24 Themis by two independent groups (Campins et al. 2010, Rivkin and Emery 2010). The presence of any ice on asteroid 24 Themis, particularly over a significant fraction of its surface, is puzzling because of the instability for exposed water ice at Themis's heliocentric distance ( 3.2 AU). Nevertheless, there are several possible sources for this unstable ice and identifying them is likely to be diagnostic of important processes on primitive asteroids. The identification of the source of surface ice on this and other asteroids will be one of the main goals of this workshop. In addition, understanding the abundance of water in this region of the asteroid belt can constrain models of Solar System formation, and may also be related to the origin of Earth's water and organic molecules. In fact, it has been suggested that the bulk of the water presently on Earth was carried by a few planetary embryos formed in the outer asteroid belt (Morbidelli et al. 2000).

Exploration Radio et Plasma de la Magnétosphère de Jupiter et de Ganymède

2026-04-16T00:00:00Z

Organisateur : Baptiste Cecconi (LESIA, tel : 77 59)

Dans le contexte de la préparation à la mission EJSM (Europa Jupiter System Mission), les
laboratoires français impliqués dans l'étude des plasmas planétaires participent activement aux
études préparatoires à cette mission. Cet atelier arrive à la fin de cette phase d'étude, quelques mois
avant l'ouverture de l'Appel d'Offre instrumental de l'ESA pour cette mission.
Grâce à l'expertise (à la fois scientifique et technique) présente dans les laboratoires, la communauté
française a été très largement impliquée dans l'étude de la magnétosphère de Jupiter et de celle de
Ganymède. Nous proposons de passer en revue les connaissances actuelles sur ce sujet et les
théories développées pour interpréter les observations. Seront mentionnés les résultats obtenus grâce
aux précédentes missions spatiales (notamment Voyager, Galileo, Ulysses ou Cassini) et aussi grâce
aux instruments sols (comme le réseau décamétrique de Nançay). De multiples thèmes seront
abordés : émissions radio, phénomènes de transport de plasma, interaction satellite-Jupiter, contrôle
du Vent Solaire, dynamique magnétosphérique, magnetosphère de Ganymède, physique aurorale,
observation aurorales (IR, UV, X...), mesures locales du plasma (bruit thermique, sonde de Langmuir,
détecteur de particules, champ magnétique, champ électrique continu, ondes de plasma, courants...).
Dans un second temps, nous présenterons les objectifs scientifiques plasma de la mission EJSM, en
mettant l'accent sur les résultats des études instrumentales menés dans les laboratoires français
(IPAG, IRAP, LATMOS, LESIA, LPC2E, LPP...) et liées au thème de l'atelier. La mission JUNO
(lancement prévu en Août 2011) sera aussi évoquée.
Le but de l'atelier est ainsi de faire un bilan scientifique avant l'Appel d'Offre de l'ESA pour EJSM, et
de renforcer les synergies scientifiques entre les équipes françaises intéressées. Nous avons aussi
invité les ingénieurs qui seront appelés à concevoir les instruments que nous enverrons vers Jupiter,
afin de les associer très tôt dans la définition de l'instrumentation, de les familiariser aux objets que
nous allons observer et aux contraintes observationnelles et instrumentales que nous rencontrerons.

AVOCADO : A Virtual Observatory Census to Address Dwarfs

2026-04-16T00:00:00Z

Oragisateur : Marc Huertas (GEPI, tel : 76 04)

Les galaxies naines sont, de loin, les galaxies les plus abondantes dans lʼUnivers
local. Dans la vision actuelle, elles se seraient formées dans des halos de matière
sombre vieux et peu massifs qui étrangement auraient été très peu efficaces dans la
transformation de baryons en étoiles au cours de leur existence. Elles représentent
donc dʼexcellents laboratoires pour lʼétude des processus de formation stellaire et
des effets de “feedback” susceptibles de ralentir ces processus.
Les propriétés de ces objets sont cependant mal connues, tant dʼun point de vue
théorique comme observationnel. En effet, les simulations cosmologiques ne sont
pas capables de reproduire la formation de galaxies naines car la reproduction de la
physique baryonique à des échelles si petites nécessiterait dʼune résolution
inabordable avec les machines actuelles. Dʼun point de vue observationnel, les
études détaillées dʼun échantillon significatif de galaxies naines restent extrêmement
difficiles car leur observation est très coûteuse en temps de télescope à cause de
leur faible luminosité intrinsèque.
Le projet AVOCADO (“A Virtual Observatory Census to Adress Dwarfs Origins”, PI R.
Sánchez-Janssen) utilise la puissance de lʼObservatoire Virtuel pour construire, pour
la première fois, un échantillon homogène, multi-longueur dʼonde et statistiquement
significatif de quelques milliers de galaxies naines proches (-18 < Mi < -14) afin
dʼétablir des conclusions robustes sur la formation et lʼévolution de ces objets. En
utilisant en effet des données publiques de plusieurs sondages et les outils fournis
par lʼObservatoire Virtuel (VOSA) nous avons pu reconstruire les distributions
spectrales dʼénergie (SED) de lʼUV à lʼIR proche (GALEX+SDSS+2MASS) et les
ajuster avec des modèles de populations stellaires, permettant ainsi dʼestimer des
paramètres comme la formation stellaire, lʼage ou la métallicité de ces objets. A cela,
on ajoute des paramètres structuraux extraits des images optiques qui permettent
également une classification morphologique. Cet échantillon unique, combine avec
une étude détaillée de lʼenvironnement de chaque galaxie doit permettre une
meilleure compréhension des origines des galaxies naines et de leur(s) chemins
évolutifs. AVOCADO est destiné à devenir un échantillon de référence pour les
modélisateurs et pour des futures études à plus grand redshfit.

Prominence Cavities

2026-04-16T00:00:00Z

Organisateurs : Laurel A. Rachmeler (HAO, NCAR), Guillaume Aulanier (LESIA)

The magnetic structure of prominences is greatly debated in the solar community. Generally they are believed to be either twisted flux ropes or sheared arcades with little or no twist (e.g. Gibson and Fan, 2006 ; Aulanier and Demoulin, 1998, Van Ballegooijen, 2004). Because to date coronal magnetic field observations have been unavailable, the answer to this question has relied on extrapolations from photospheric fields and on high energy observations where bright structures are thought to follow lines of magnetic force.
The High Altitude Observatory (HAO) in the National Center for Atmospheric Research (NCAR) in the United States has recently deployed a new instrument, the Coronal Multi-Channel Polarimeter (CoMP), which measures linear and circular polarization in coronal infra-red (IR) lines off the limb of the sun (Tomczyk et al, 2008). These measurements are signatures of the magnetic field, and may be used to differentiate between the flux rope and the sheared arcade prominence models. With the use of a new FORWARD suite of IDL codes, developed at HAO with international collaborators (ISSI workshop), we can now create simulated CoMP, EUV, and other observables that can be directly compared to observational data.
The goal of this workshop is to bring together numerical modelers and observers from several world-leading groups, including HAO and LESIA, to test various theoretical, analytic, and numerical models of the magnetic field surrounding prominences and to analyze the CoMP coronal polarization signatures from each model.
The polarization signatures in the corona are not trivial to invert into magnetic field, thus it is extremely useful to forward model theoretical magnetic field configurations which can be directly compared to observable quantities. These can then also be compared to other observables calculated in the FORWARD code, such as EUV images. Material at prominence temperatures is not within the range of the Fe XII 1074.7 nm coronal line (the line calculated in the CoMP FORWARD model), and so we will mainly focus on the magnetic morphology of the plasma surrounding the prominence itself.
It has been shown that when a prominence on the limb is along the line of sight, a coronal cavity is often observed in EUV pass-bands (Hudson et al, 1999). Coronal cavities in some models, including those models used at LESIA, are fundamental aspects of prominence magnetism. Although relatively low in intensity, they are only depleted in density by about a factor of two compared to surrounding bright structures, and are brighter than coronal holes. Because of this low density, cavities are extremely sensitive to orientation (Gibson et al, 2010), and the same is true of the polarization signature. In order to address the question of sheared vs. twisted fields, we need to observe prominences where the axis is along the line of sight. Thus, the appearance of a cavity in
EUV is a good indication that the prominence is in the correct orientation and would be an ideal candidate for comparison to models.
There are multiple questions that can be addressed during the workshop, and they can be tailored to the specific participants. Among these questions are :
•Do different models of prominences predict different CoMP linear and circular polarization signals ?
•How do CoMP polarization signals correspond to EUV images — e.g. discrete O or C-shaped bright loops inside cavities ? This question is motivated by recent Solar Dynamics Observatory (SDO) observations of such bright and dynamic features.
•Do prominence tops correspond to the center of these concentric circles and/or CoMP linear polarization depletions, and hence the axis of the magnetic field ? This prediction comes from idealized highly twisted and/or nearly axisymmetric flux rope models. Although we cannot directly forward model the prominences in this particular wavelength of polarized light, we can „paint‟ the dips in the field which are expected to correspond with the bright prominence material.
•Can we distinguish not only between twisted and untwisted ropes, but also put limits on the amount of twist in these ropes ?
•What is the relationship between prominences and cavities, are they separate or unified magnetic structures ?
As stated earlier, the data from CoMP are new, but will to greatly enhance the field of prominence and cavity magnetometry. We want to bring this new data directly to the modelers to help solve the outstanding questions about prominence magnetic topology.

Science with a Fast Multi Objects Photometer (F-MOP)

2026-04-16T00:00:00Z

Organisateur : Francoise Roques (LESIA, tel : 71 08)
Il s'agit de préciser les domaines scientifiques interessés par le projet UltraPhot, Fast Multi-Object Photometer soumis à l'ESO dans le cadre d'un upgrade des instruments MOS
des VLT :
Cet instrument permettra de faire de la photométrie rapide en 3 couleurs visibles multi-objets
dans le grand champ de l'instrument FLAMES. Les thématiques concernées sont
nombreuses :
• Exploration of Outer Solar System Objects (Kuiper Belt, Oort (…)

- Science with a Fast Multi Objects Photometer (F-MOP) / descriptif_rubrique