Seminars

List of seminars in Ile-de-France: February-March 2023

Please consult the online calendar, as cancelations can occur during this season of strikes!

1 February 2023, 14:30

InSight et SEIS : Premier bilan après 4 années de surveillance sismique de Mars
Philippe Lognonné (Univ. Paris Cité, IPGP, CNRS)
Ecole Normale Supérieure, Salle Jaurès, 29 rue d’Ulm, 75005 Paris

Summary
Pendant près de 4 ans, la mission NASA InSight, portée par le Jet Propulsion Laboratory, a exploré la structure interne de Mars avec son instrument principal, le sismomètre SEIS sous responsabilité scientifique de l’IPGP et maitrise d’œuvre CNES. Avec plus de 1300 événements sismiques, dont plus de 30 de magnitude supérieure à 3, le plus fort de magnitude 4,7, il a permis d’identifier une forte activité sismique dans Cerberus Fossae et d’inverser les mécanismes au foyer pour une demi-douzaine de séismes. Ces analyses sismiques, ainsi que les modélisations récentes du champ de gravité, suggèrent que cette région de Mars pourrait être le siège d’un panache mantellique encore actif. SEIS a également détecté de nombreux impacts de météorites, confirmés par l’imagerie orbitale, y compris pour quelques impacts dont les cratères dépassent 100m de diamètre. Pour la première, ces données ont permis d’élaborer des modèles sismiques de la croûte, du manteau et du noyau, et ce pour une autre planète tellurique que la Terre, nous permettant de mieux comparer la structure interne de Mars à celle la Terre et de la Lune, tant pour la taille de leurs noyaux que celle de leur lithosphère thermique, permettant ainsi de poser de nouvelles bases en planétologie et sismologie comparée. Nous concluons en présentant les futures missions de sismologie planétaire, tant sur la Lune, avec la mission FarSide Seismic Suite et les perspectives d’Artemis, que sur les satellites des planètes géantes, Titan pour Saturne ou Europe pour Jupiter, ainsi que les perspectives sur la Lune de détection d’ondes gravitationnelles avec des capteurs sismiques.

[CANCELLED] 7 February 2023, 15:00

Turbulence in the atmosphere of Mars and Titan
Aymeric Spiga (Laboratoire de Météorologie Dynamique, Sorbonne Université)
IPGP Planetary and Space Sciences, Bâtiment Lamarck B, 35 rue Hélène Brion, Paris

Summary
Mars and Titan have both vastly distinct environments from the Earth’s, yet they exhibit atmospheric turbulent phenomena akin to the ones we experience at the surface of our planet. What is particularly interesting on Mars and Titan is that turbulence is somewhat a distant exotic cousin of Earth’s atmospheric turbulence, with many different aspects that allows for a rich comparative study. This study can be placed in a context of planetary exploration and multi-disciplinary planetary science.

Connection details
Zoom link
Meeting ID: 876 7331 0489
Passcode: 856642

In-person directions
The IPGP Planetary and Space Sciences seminar series is held in the building Lamarck B that is part of the Université Paris Cité - Campus des Grands Moulins near the BnF (Bibliothèque Nationale de France). We are not at the main IPGP campus near the Jardin des Plantes and the Jussieu metro station. You do not need a badge to enter this building. You only need to go to 35 rue Hélène Brion, and once in the lobby of the main entrance, take the elevators on the right to the 5th floor. Exit the elevator and take the corridor to the right. The seminar room is number 522.

13 February 2023, 15:00

Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars
Adrien Broquet (Univ. of Arizona)
IPGP Origins seminar (online only)

Summary
Although the majority of volcanic and tectonic activity on Mars occurred during the first 1.5 billion years of its geologic history, recent volcanism, tectonism and active seismicity in Elysium Planitia reveal ongoing activity. However, this recent pulse in volcanism and tectonics is unexpected on a cooling Mars. In this talk, I will present observational evidence and geophysical models demonstrating that Elysium Planitia is underlain by an ~4,000-km-diameter active mantle plume head driving the regional volcanic and seismic activity. The inferred plume head characteristics are comparable to terrestrial plumes that are linked to the formation of large igneous provinces. These results demonstrate that the interior of Mars is geodynamically active today. Studies using data collected by InSight have to consider the presence of the plume.

Connection details
Zoom link
Meeting ID: 946 7946 3245
Passcode: C0sGse

14 February 2023, 15:00

The thermodynamic state of the protolunar disk after the giant impact
Razvan Caracas (Insitut de Physique du Globe de Paris)
IPGP Planetary and Space Sciences, Bâtiment Lamarck B, 35 rue Hélène Brion, Paris

Summary
We study the behavior of a multi-component silicate fluid with bulk silicate Earth composition at conditions typical for the giant impact that generated the protolunar disk. We find that the Earth’s protolunar disk reached the supercritical state of the silicate mantle. As such, the Earth, and most rocky planets, will traverse a temporary state that lacks a surface defined by a magma ocean-atmosphere boundary. The atomic structure of the silicate fluid varies with the radius within the disk due to strong pressure and temperature gradients. Fluffy short-lived chemical species dominate the outer parts of the disk, and long-lasting dense polymers abound in the deeper parts. During cooling, when the temperature and density profile of the disk intersect the liquid-vapor dome, liquid and vapor start to separate, the disk evolves as a two-phase system, and the central body starts to condense. The composition of the post-impact atmosphere is dominated by species along the mantle vapor curve.

Connection details
Zoom link
Meeting ID: 876 7331 0489
Passcode: 856642

21 February 2023, 15:00

Nudging virtual planets
Nicolas Coltice (Ecole Normale Supérieure, Paris)
IPGP Planetary and Space Sciences, Bâtiment Lamarck B, 35 rue Hélène Brion, Paris

Summary
Tectonics, climate, and landscapes are symptoms of underlying intrinsic properties of planets. Looking at the Earth in recent times, I will propose ways to nudge virtual planets towards real ones.

Connection details
Zoom link
Meeting ID: 876 7331 0489
Passcode: 856642

23 February 2023, 15:00

Where was the Moon? A fresh look at the tidal evolution of the early Earth-Moon system
Jun Korenaga (Yale University)
IMCCE, AstroGeo seminar (online only)

Summary
The early evolution of the Earth-Moon system prescribes the tidal environment of the Hadean Earth and holds the key to the formation mechanism of the Moon. Estimating its early state by backtracking from the present, however, suffers from considerable uncertainties associated with ocean tides. Tidal evolution during the solidification of Earth’s magma ocean, on the other hand, has the potential to provide robust constraints on the Earth-Moon system before the appearance of a water ocean. I will show how energy dissipation in a solidifying magma ocean results in limited lunar recession and suggest that the Moon was probably still at the distance of approximately 7-9 Earth radii at the beginning of subsolidus mantle convection. With a plausible range of ocean tides, the Moon must have gained nearly half of the present-day orbital distance during the Hadean, suggesting a rapidly changing tidal environment in the early Earth. Limited lunar recession during Earth’s magma ocean will also help to evaluate various hypotheses proposed for the origin of lunar inclination.

Connection details
Zoom link
Meeting ID: 88928171993