A New Mechanism for H2o Precipitation on an Earlier

Introduction: There is considerable evidence derived from both orbital observations of geomorphology and geochemical and mineralogical investigations by the Mars Exploration Rovers (MER) that suggests condensed H 2 O was present at some location on the Martian surface in the past history. Orbital measurements by the Gamma Ray Spectrometer on board the Mars Odyssey spacecraft also indicate that abundant hydrogen, most probably in the form of ground ice is of still present in the shallow subsurface over much of the planet. In the absence of a massive early greenhouse effect, the wide spread precipitation of H 2 O by rain appears improbable based on the one-third lower luminosity of the sun that is thought to have characterized this period. For this reason, it is interesting to consider potential alternative mechanisms for long distance atmospheric transport and precipitation of H 2 O that may have occurred even under much colder early climate conditions. Icy volcanic ash fallout: The eruption of ancient Martian volcanoes likely resulted in the atmospheric introduction of magmatic H 2 O (as water vapor) and ash aerosol substrate for its prompt nucleation and condensation under presumed low temperature early environmental conditions. High altitude winds at altitude could have then transported the icy ash over considerable distances, allowing it to fall out over large regions of the planet. Contemporary Martian dust storms illustrate the potential extent of volcanic ash transport following a volcanic