Title:

Condensation of volatiles in the presolar nebula: forms, and implications for the delivery of volatiles to the giant planets and their satellites.

Authors:

Mathieu Choukroun

Abstract:

The diversity in chemical composition of Solar System objects, and particularly in volatiles in the outer regions, is difficult to explain by a simple condensation process within the presolar nebula. Indeed, enrichments and deficiencies in volatile elements relative to the solar abundances have been observed: 1) in comets, where N2 and Ar are poorly concentrated compared to CO, unlike what condensation of pure ices upon cooling would predict; 2) in giant planets atmospheres, as observed by the Galileo spacecraft at Jupiter – which shows a bulk enrichment by a factor of 2-5 from the solar abundances in C, N, O, S, and noble gases –, or by the Cassini spacecraft at Saturn – with selective enrichments and depletions in the same compounds; 3) in icy satellites, although chemical reactions during the accretion and the evolution may have altered the initial abundances and isotopic compositions. This review presentation will focus on the forms of ices that may have formed within the presolar nebula (i.e. pure ices, gas-laden amorphous ice, clathrate hydrates) and, in the framework of recent solar nebula condensation models, how these forms may have affected the delivery of volatiles (timing, relative abundances) to giant planets circumplanetary disks and their satellites. A specific emphasis will be made on the limitations that our current knowledge of these volatile condensates impose on formation models.

The author acknowledges support from a NASA Postdoctoral Program Fellowship, administered by Oak Ridge Associated Universities. This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged.