nai

Project Progress

The focus of this work is to understand the organic chemical evolution of extraterrestrial organics, beginning in the solar nebula, through to delivery to the Earth.

• I have developed chemical models for protoplanetary disks in order to understand the environment that allowed volatile-rich planetesimals to carry water and organics to habitable planets. Our findings are so far consistent with the chemical and isotopic composition of the most primitive meteorites.
• The dynamical parameters (orbital eccentricity, inclination, semimajor axes, masses) of the giant planets determine where, when, and how terrestrial planets form and accrete the ingredients for life (water and organic carbon). Giant planets control everything: where the sources of the water and organics are (extrasolar asteroid belts, “Kuiper belts” and “Oort clouds”), if and when water and organics are delivered to habitable planets, and whether Earth-like planets form in the habitable zone at all! In our own solar system, even Saturn has a big role in this process. Coupled with evolutionary models for nebula chemistry and physics, we can determine from first principles what the water and organic content of the source regions will be. N-body simulations designed to follow the long-range time evolution of these slowly dynamically unstable regions tell us when, and from where, massive comet and asteroid impacts will occur.
• We studied the chemistry of giant impacts in delivering organic carbon to habitable planets. When large (>1 km) water and carbon-rich objects such as comets or carbonaceous chondrites impact the Earth, the energy of the impact was thought to drive all of the carbon into CO, the most strongly bound molecule, which participates in no further chemistry. However, in our models, we find that CO does indeed react over shorter timescales when exposed to catalytically active dust grains.