Formation and deposition of volcanic sulfate aerosols on Mars

Abstract

Sulfurous gases released at the surface of Mars during episodes of volcanic activity would be naturally transported into the upper levels of the Martian atmosphere (20‐ to 30‐km altitude) owing to the synoptic convergence of lower‐level winds in the Tharsis region of the planet. The circulation of the upper atmosphere would globally disperse such gases over time scales of 25 earth days. The rate limiting step in sulfate aerosol formation on Mars is inferred to be the gas phase oxidation of SO 2 which is accomplished via chemical reactions with O, OH, and HO 2 . Under present‐day atmospheric conditions aerosol formation would occur over periods of several thousand earth days. However atmospheric concentrations of odd hydrogen species (OH, HO 2 ) should increase significantly during periods of persistent surface volcanism. Under these circumstances sulfate aerosol formation could occur on time scales of several hundred earth days. Submicron‐sized aerosol particles would circuit Mars several dozen times before they are removed from the atmosphere by gravitational forces. Such aerosols would be globally dispersed and would be deposited over a wide range of equatorial and mid‐latitudes. Volcanic sulfate aerosols on Mars are inferred to consist of liquid droplets and liquid‐solid slurries containing aqueous solutions of sulfuric acid. These acidic solutions would be chemically reactive and would trigger leaching processes within surface materials upon deposition. Sulfate aerosol de…