If Mars originally had a warm, wet climate; then inorganic (or organic {!}) chemical processes would have rapidly consumed Mars' CO2 inventory and reacted with surface rocks to form extensive deposits of Carbonates, amounting to at least 50 metres thickness worldwide.

The Paradox: Despite extensive spectroscopic and chemical tests, only trace amounts have been found.

The conventional solution does not exist. Various authors propose that the deposits are all buried by dust and polar ice, despite many impact crater penetrations planetwide. Others suggest that the carbonate formed early and was pulverised and mixed through the regolith by the closing phase of the grand bombardment (yet this disagrees with the evidence for fluid flow much later in Mars' history - the outburst "floods"). One of the major focus points of the current Mars exploration programme is an emphasis on chemical and spectroscopic searches for buried, hidden, cryptic, and otherwise "missing" carbonate.

The White Mars solution to the paradox: Since Mars was never warm and wet, there was never liquid water (except transiently on early Mars associated with major impacts, and in the subsurface associated with igneous intrusions), and hence no surface carbonate deposits formed. The CO2 remains in the form of CO2 ice in the subsurface, where it is exposed in deflation zones, impact craters and collapse  features. When exposed, it sublimes into the atmosphere and joins the polar CO2 ice cycle.
 

      Created: May 2002
      Last modified: May 2002
      Authorised by:  Head, Earth Sciences

      Maintained by: Nick Hoffman
      Email: nhoffman@unimelb.edu.au