Zusammenfassung
Asteroids and comets that are vaporized during hypervelocity impact
events can inject large masses of S into the stratosphere where it
can potentially affect the radiation budget of the Earth, alter the
chemistry of the ozone layer, and eventually be converted to sulfuric
acid rain. Relatively small carbonaceous asteroids, 0.3 km in diameter,
contain 5 times more S than the entire modern stratosphere and these
objects hit the Earth at an average rate of 1 per 10,000 years. Larger
impact events, capable of injecting 10(15) g of S into the stratosphere,
occur at an average rate of 1 per 1 million years. Calculations indicate
there is sufficient O and H in the vapor plumes of most impact events
to convert the S to sulfuric acid aerosols. If this conversion occurs,
then the larger impact events could depress mean surface temperatures
by more than 2 degrees C for 3 years or longer.
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