| 19110 |
abstract |
The early history of the terrestrial planets was punctuated by a period of heavy bombardment.
Frequent large impacts condensed in a short, 0.02–0.5-Ga-long time period resulted
in heavily cratered planetary surfaces. In volatile-bearing planetary crusts, each
of these large impacts created a volume of hot rock and melt that drove vast subsurface
hydrothermal systems. In Mars' basaltic crust, these systems produced a variety of
alteration phases, the nature of which we explored with thermochemical modeling. Using
the computer code CHILLER, we found a variety of oxides, hydroxides, and hydrous and
water-free silicates resulting from the hydrothermal alteration. The main hydrous
silicates are serpentine, chlorite, nontronite, and other clay minerals. Some of the
resulting assemblages contain up to 15 wt% bound water. Our results constrain the
temperature and water rock ratio at the time of alteration and compare well to the
mineral assemblages found on Mars by OMEGA (Observatoire pour la Minéralogie, l'Eau,
les Glaces, et l'Activité) and CRISM (Compact Reconnaissance Imaging Spectrometer
for Mars) and, therefore, provide an interpretative framework for analyzing Martian
mineralogy from orbital data. Our results also provide a geological template needed
to select landing locations for future missions that search for water and energy sources
associated with potential habitats on early Mars. |