Publication Type:
Poster
Source:
(2007)
Abstract:
The length of time that Martian rocks were exposed to liquid water is of
great interest because it influences the interpretation of the climate history and
potential for life on that planet. The presence or absence of primary minerals
may provide constraints for the presence and duration of liquid water on Mars. If
pH values of terrestrial and Martian weathering solutions are similar, then mineral
persistence times on Mars can be assumed to be greater than or equal to those
on Earth: olivine (~10 ka), glass (~250 ka), pyroxene (~1Ma), plagioclase (~5Ma).
However, Mars weathering solutions may have been more acidic than on Earth.
Relative mineral weathering rates observed for basalt in Svalbard (Norway) and
Costa Rica are consistent with observed pH. This suggests that the pHdependence
of laboratory dissolution rates can be used to extrapolate relative
mineral persistences to lower pH values possible on Mars. If the pH of
weathering solutions on Mars is greater than ~2, we would expect glass to
dissolve less quickly than olivine. Observations of the presence or absence of
weathered olivine and glass may therefore be useful to interpret Martian solution
pH. Weathering profiles can be interpreted using reactive transport modeling to
calculate duration of weathering: the minimum duration of exposure to weathering
fluid is calculated to equal 22ka for a putative weathering rind on Mars rock
Humphrey analyzed by the Mars Exploration Rover within Gusev Crater. The
reactive transport modeling of weathering profiles on Mars is a novel approach to
study that planet’s aqueous history, and highlights the imperative for future depth
profiles on Mars.
