DPS 35th Meeting, 1-6 September 2003
Session 38. Comets V
Poster, Highlighted on, Friday, September 5, 2003, 3:30-6:00pm, Sierra Ballroom I-II

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[38.16] Passing through a Giant Molecular Cloud Snowball Glaciations produced by interstellar dust.

A.A. Pavlov, O.B. Toon (Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder), A.K. Pavlov (Laboratory of Nuclear Space Physics, Ioffe Physical Technical Institute, Russia), J. Bally (Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder), D. Pollard (Earth System Science Center, Pennsylvania State University)

In its motion through the Milky Way Galaxy, the Solar system encounters an "average"-density (>330 H atoms/cm3) Giant Molecular Cloud (GMCs) approximately every ~108 years and a "dense" (>2x103 H atoms/cm3) GMC every ~109 years and will inevitably encounter them in the future. If the colliding GMC were dense enough (>330 H atoms/cm3), the heliosphere would be suppressed within 1 A.U. (or entirely collapsed) and the Earth atmosphere would be exposed to the flux of small interstellar dust particles. We calculate the magnitude of dust fluxes into the Earth atmosphere during such encounters and evaluate their climatic significance. We found that collisions with "dense" (>2x103 H atoms/cm3) GMCs result in high dust fluxes (>50 times present IDP flux). We then modeled particles' settling and coagulation within the atmosphere and calculated the steady state dust size/number density distribution in the stratosphere. Particles would effectively absorb and scatter the sunlight and therefore dramatically cool the surface. We performed radiative transfer simulations and determined the magnitude of this effect. We found that the stratospheric dust layer from such interstellar particles could provide enough radiative forcing (9-15 W/m2 at the tropopause level) to trigger the runaway ice-albedo feedback that results in global Snowball glaciations (Neoproterozoic glaciations). More frequent collisions with less dense GMCs could still cause "moderate" ice ages.


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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.