Solar system linked to a gigantic interstellar cloud during the past 500 m.y.: Implications for a galactic theory of terrestrial catastrophism
Abstract
Modern investigations have revealed that the galactic environment of the Sun may have played a role in climatic and geological changes on the Earth through time. Here I present the results of a model of the local system of gas and stars, in which the Sun is gravitationally linked to a gigantic interstellar cloud during the past 500 m.y. The Sun would have been captured by the supercloud during the cloud's process of formation ca. 500 Ma, remaining linked to it. The original supercloud, with a mass of 2 x 107 solar masses, has been forming stars and evolving in the solar neighborhood under the influence of the pressure of external gas and shear due to the galactic differential rotation. In our model, Gould's belt, the local arm, and the Sirius supercluster, the main subsystems of the local system, would have been formed within the postulated supercloud. We propose a variation of the Rampino and Stother mechanism to explain the 26 m.y. quasiperiodicity of mass extinctions and the abrupt increase in the production rate of lunar craters over the past 400 m.y. We suggest that perturbations on the Oort comet cloud caused by encounters with intermediate-sized clouds of the supercloud about the extremes of the Sun motion perpendicular to the galactic plane could generate periodic comets showers on the Earth, in agreement with the apparent cyclicity in the mass extinctions and geological records.
- Publication:
-
Geological Society of America Special Papers
- Pub Date:
- 2002
- Bibcode:
- 2002GSASP.356..679O
- Keywords:
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- comets;
- mass extinctions;
- terrestrial catastrophism;
- solar neighbourhood;
- interstellar clouds;
- Gould's belt