80% of N2 per breath : where does it come from ?

Séminaire IPAG de Pierre Hily-Blant (IPAG), jeudi 26 novembre 2020, 11h00, IPAG seminar room

Because protoplanetary disks provide the primitive material of planets and smaller bodies, their chemical composition and the processes shaping it have become key objectives to understand how and when planetary system bodies form. However, the bulk ratio of nitrogen prevailing in the protosolar nebula (PSN) has never been found in comets. Extremely 15N-rich reservoirs of nitrogen such as found in micron-sized inclusions in chondrites can not be explained by current chemical models. Thus, the origin of nitrogen in the solar system remains elusive.

These problems raise general questions, among which :

• how and when the various isotopic reservoirs of nitrogen in the PSN were formed ;
• how comets recorded, or kept, only one, minor, reservoir.

In this talk, I will present the sucess and failures of our current view of the origin of nitrogen in the solar system. We will track the reservoirs of nitrogen from prestellar cores to disks and primitive solar system bodies, while trying to adopt a language common to cosmochemistry and astrophysics. In doing so, I will show the latest results from models and observations, from our team and worldwide groups. Although the big picture could appear self-consistent, I will try to stress the limits and fundamental failures of understanding of nitrogen chemistry and isotopic ratios. Finall, observational, theoretical, and modeling, potential lines of investigations will be shared.