Collaboration on the Evolutionary Chemistry of Protoplanetary Disks

Collaboration on the Evolutionary Chemistry of Protoplanetary Disks S. Davis, D. Richard, T. Lee We plan to investigate chemical networks (up to hundreds of species, thousands of reactions) associated with the broad field of Cosmochemistry as applied to protoplanetary disks. These disks represent planetary incubators and sites of specialized chemical reactions (possibly organic and pre biotic precursors). They are complicated by a wide range of dynamic environments ranging from 20 to 2000 K and number densities from 10^5 to 10^14 1/cc which, in turn, support a very wide variety of chemical reaction time scales. We discuss efforts on determining the key reaction steps governing formation processes of observational species (CO) and astrobiological interesting species (H 2 O and H 2 Oice).

the Protoplanetary Disk About 4, 000, 000 years ago

Contours of Log(T) showing effect of viscous heating z, AU Active Disk: Viscous shear Passive Disk: Central star & IR grain heating r, AU

Contours of Log(n, cm-3) z, AU Active Disk: Viscous shear Passive Disk: Central star & IR grain heating r, AU

Chemical Network (at each point in the Nebula) l CHOS: 65 R x 708 S l UMIST: 396 R X 3740 S (also OSU New. Std. Model)

Typical Early Result Observation Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star Lk. Ca 15 Qi, Chunhua; Kessler, Jacqueline E. ; Koerner, David W. ; Sargent, Anneila I. ; Blake, Geoffrey A. Ap. J, Nov 2003 We present Owens Valley Radio Observatory Millimeter Array lambda=3. 4 -1. 2 mm dust continuum and spectral line observations of the accretion disk encircling the T Tauri star Lk. Ca 15. . Imaging of the fairly intense emission from the lowest rotational transitions of CO, 13 CO, and HCO+ reveals a rotating disk substantially larger than that observed in the dust continuum. Emission extends to ~750 AU Sensitivity Analysis of CO species Flared disk code & chemical network 65 S X 708 R T = 188 K; n = 0. 23 E+14 48. 4% HCO+ + H 2 O -42. 8% H 3+ + CO -4. 7% HCO 2+ + CO -2. 4% OH . . . . + CO -> H 3 O+ CO -> HCO+ H 2 -> HCO+ CO 2 -> CO 2 H

NRA Solicitations of Interest l Cosmochemistry. l Origins. l Exobiology?