Contribution Contributed Talk
Revealing the Ancient Heritage of Solar System Ices
- Dr. L. Ilsedore CLEEVES
- Dr. L. Ilsedore CLEEVES (CfA)
Identifying the formation history of the solar system's water and simple organic content is central to understanding the conditions that fostered life in at least one planetary system, and how common such conditions are elsewhere. A key clue in this pursuit is that both water and organics in primitive solar system bodies are characteristically enhanced in their deuterated isotopologue relative to standard (D/H), where the organics are typically more enriched than water. This isotopologue signature points to formation in very cold ($T<50-100$ K) environments, facilitated by the presence of ionizing agents, i.e., cosmic rays, radionuclide decay, and X-rays. These requirements point to two possibilities: formation within the protoplanetary disk or inheritance from the parent molecular cloud. Using a comprehensive treatment of disk ionization, we find ion-driven D/H fractionation pathways in the disk are inefficient, inhibiting both the formation of deuterated water and organics especially in the midplane. We have also isolated potential chemical explanations for the D/H differences between water and organics. We find that while a significant fraction of water ice was likely inherited from the parent molecular cloud, organics have a much more complex and varied history. Our findings imply that - if the solar system’s formation was typical - interstellar water and organic ices are available to all nascent planetary systems.