From planet formation to thermodynamic constraints on the first genetic code

Ralph Pudritz

March 15, 2010

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Abstract: Protoplanetary disks provide the initial conditions for planet formation as well as for their prebiotic states. In this talk I will examine both how planets form and how terrestrial planets come to be ‘equipped’ with water and biomolecules. Standard models for planet formation in dusty, gaseous disks reveal that planets rapidly migrate during their formation. This process is so efficient that planets risk plunging into their central stars within a million years. I shall review observations and ideas of what controls the process of exoplanet formation and migration. I will then present our own recent simulations of migrating and accreting planets in radiatively heated protostellar disks containing dead zones – regions where turbulence is strongly suppressed. We have discovered that both the density and thermal structure of disks with dead zones act as effective brakes that prevent the rapid loss of planets to their central stars. The radiatively heated natal disks that produce planets may also be significant factories for the synthesis of biomolecules such as amino acids, which may be delivered to planets by cometary or meteoritic bombardment. We have recently discovered some general thermodynamic constraints on the synthesis of amino acids in a variety of prebiotic environments. This provides insight into the environments which produced biomolecules for early life and possible constraints on the nature of the first genetic code.