When
3:30 p.m., Sept. 30, 2008
Where
Kuiper Space Sciences Building 308
Professor Michael J. Drake (LPL) is the scheduled speaker.
Abstract:
The origin of water in the inner solar system is not understood. The accretion disk from which our planetary system formed was composed of solid grains bathed in a gas dominated by hydrogen, helium, and oxygen. Some of that hydrogen and oxygen combined to make water vapor. It is believed that temperatures were too high in the accretion disk in the region of the terrestrial planets for hydrous phases to be thermodynamically stable. Thus water must have been delivered in some other form.
Water could have been delivered from the earliest stages of the solar system when a disk of gas and dust surrounded a nascent Sun, to late in planetary formation by collisions of planets with hydrous asteroids or comets. I will discuss direct implantation of H2 and O2 from the gas, adsorption of water directly from the gas, and late delivery of hydrous asteroids and comets. All are potential sources of water. Isotopic and elemental ratios will be used to test these hypotheses. The idea that water might be adsorbed directly from the gas in the accretion disk is a relatively new idea, and I will examine this possibility quantitatively by exploring the adsorption dynamics of water molecules onto forsterite surfaces via kinetic Monte Carlo simulations. I conclude that many Earth oceans of water could be adsorbed. With current knowledge it is not possible to quantitatively estimate the relative contributions of these four processes to the water budget of the Earth.
Abstract:
The origin of water in the inner solar system is not understood. The accretion disk from which our planetary system formed was composed of solid grains bathed in a gas dominated by hydrogen, helium, and oxygen. Some of that hydrogen and oxygen combined to make water vapor. It is believed that temperatures were too high in the accretion disk in the region of the terrestrial planets for hydrous phases to be thermodynamically stable. Thus water must have been delivered in some other form.
Water could have been delivered from the earliest stages of the solar system when a disk of gas and dust surrounded a nascent Sun, to late in planetary formation by collisions of planets with hydrous asteroids or comets. I will discuss direct implantation of H2 and O2 from the gas, adsorption of water directly from the gas, and late delivery of hydrous asteroids and comets. All are potential sources of water. Isotopic and elemental ratios will be used to test these hypotheses. The idea that water might be adsorbed directly from the gas in the accretion disk is a relatively new idea, and I will examine this possibility quantitatively by exploring the adsorption dynamics of water molecules onto forsterite surfaces via kinetic Monte Carlo simulations. I conclude that many Earth oceans of water could be adsorbed. With current knowledge it is not possible to quantitatively estimate the relative contributions of these four processes to the water budget of the Earth.
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