CEISAM and LPG are developing an experimental approach to study insoluble organic matter in ice satellites

It is only very recently that evidence has been obtained suggesting that a significant amount of insoluble organic matter is present in solar system objects that are sufficiently distant from the sun for water to be present in the form of ice (comets, ice satellites of giant planets).

Winners of the 80 | PRIME call of the CNRS (MITI), a team of the "Laboratoire Chimie et Interdisciplinarité : Synthèse, Analyse, Modélisation" of CEISAM (Clémence Queffelec and Bruno Bujoli) and the "Laboratoire de Planétologie et Géodynamique" (Christophe Sotin, Gabriel Tobie, Olivier Bollengier and Erwan Le Menn) coordinate the project EMOI (Evolution of Insoluble Organic Matter). This research program, also conducted in partnership with the "Centre de Recherches Pétrographiques et Géochimiques", aims to characterize the transformation of insoluble organic matter "model" in conditions mimicking those present inside the satellites of giant planets (Titan, Ganymede, Callisto).

 

Figure 1
Titan’s interior structure. The rocky core is likely composed of hydrated silicates to account for the high value of the moment of inertia. It is overlaid by a hydrosphere that includes a deep salty ocean. © Titan’s Interior Structure and Dynamics After the Cassini-Huygens Mission, Christophe Sotin, Klára Kalousová and Gabriel Tobie, Annual Review of Earth and Planetary Sciences, 2021.

 

This consists in carrying out reactions between organic matter, water and hydrated silicates, in the presence or not of iron sulfides, in temperature and pressure ranges, from 100 to 600 °C and 0.01 to 5 GPa, respectively.

The EMOI project aims to help understand objects in the outer solar system by answering two key questions :

(1) can the destabilization of insoluble organic matter be at the origin of Titan's atmosphere (N2 and CH4) and can the contribution of CH4 be sufficiently late, knowing that methane has a lifetime of a few tens of millions of years in the atmosphere where it disappears by photochemical degradation ?

(2) could molecules involved in the chemistry of life, and often considered as biosignatures, have been generated from the pyrolysis of insoluble organic matter, under abiotic conditions, calling into question the biosignature nature of these molecules ?

 

> Reference : Titan’s Interior Structure and Dynamics After the Cassini-Huygens Mission, Christophe Sotin, Klára Kalousová and Gabriel Tobie, Annual Review of Earth and Planetary Sciences, 2021.

 

> Read more : Cassini-Huygens mission