Séminaire café 2022

6 jan Florence Elias (Professeure à l’Université Paris Diderot)
The physics and physical chemistry of marine foam

Very stable marine foams are regularly observed on some coastlines, as a result of the correlation of high wind events and phytoplankton bloom in the water. The role played by these foams in the ecosystem is still unknown, while a significant drop in phytoplankton biomass and biodiversity is observed in seawater when these marine foams appear. We address these issues from a physical and physico-chemical perspective through two questions. Firstly, as liquid foams are known to concentrate many types of particles due to the particle hydrophobicity or size, is it conceivable that phytoplankton, seen as a community of active particles, is also concentrated and therefore retained in the foam ? This question raises the more general question of the transport of active particles in complex environments (confined and potentially non-Newtonian). Secondly, what are the physico-chemical mechanisms at the origin of the high stability of these foams, even though the presence of a high ionic concentration, as is the case in seawater, is known to inhibit the stabilisation of foams ?
In this talk I will present recent results obtained on model systems, ongoing and planned work on this topic.
13 jan Lucia Mandon (Postdoc at LESIA (Meudon))
One year of Martian exploration : news from the Perseverance rover

On the 18th of February 2021, the Perseverance rover of the Mars 2020 mission (NASA) landed at the "Octavia E. Butler" site, on the floor of the 45 km diameter Jezero crater, an ancient Martian lake that once hosted liquid water. The goals of the mission are to characterize past environments at Jezero and search for biosignatures. These objectives will be achieved through the collection of samples to be returned to Earth by the MSR (Mars Sample Return, NASA/ESA) mission and the investigation of the rocks of the crater and beyond using the rover payload. We will present the results of nearly one year exploring the crater floor of Jezero, in particular through the “eyes” of the rover, the SuperCam instrument, which plays a critical role in the exploration strategy as it combines various remote-sensing techniques to investigate the elemental and mineralogical composition of surfaces.

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Informations Pratiques

Laboratoire : 01 40 79 45 22
Directeur : Damien Vandembroucq
Codirecteur : Philippe Petitjeans
Administratrice : Frédérique Auger (01 40 79 45 22)
Gestionnaire : Claudette Barez (01 40 79 58 53)
Courriel : dir (arobase) pmmh.espci.fr