Sulfate Brine Stability Under a Simulated Martian Atmosphere

1
Sulfate Brine Stability Under a Simulated Martian
Atmosphere
Jackie D Denson, Vincent Chevrier, and
Derek Sears
W.M. Keck Laboratory for
Space Simulation
University of Arkansas Center for Space and
Planetary Sciences, Fayetteville Arkansas

Initial Results
Background Evidence for the presence of sulfate
containing sediments on Mars dates as far back as
the Viking era. (1) Recently the Omega
hyperspectral imager on Mars Express has mapped
extensive sulfate bearing minerals to km and
sub-km resolution (Fig. 1 and 2). These
observations have shown that MgSO4-minerals are a
major component of the Martian regolith (Table
1). (2)These minerals have the ability to exist
in a variety of configurations with different
states of hydration,and could therefore play a
significant role in our understanding of the
state of water on Mars (Fig. 3).
When compared to the evaporation rates predicted
for pure water under the same conditions sulfate
brines evaporate more slowly (Fig. 4-6). Based
on our initial results this appears to be a
multifactored process as subtle differences in
temperature and humidity can lead to dramatic
differences in evaporation rate (Fig. 4 vs Fig.
5).Experimental refinements are currently
underway to develop better techniques of
controlling the humidity of our simulated
atmosphere. Crystal formation has also been
observed in highly concentrated brines. This
process of crystallization and hence the
hydration state of the MgSO4 under various
conditions will be examined by X Ray
Diffraction.
Table 1. Gendrin et al. (2005)
Fig. 4 20 Wt MgSO4 with flowing CO2
Objectives In order to better understand the
stability of sulfate brines on Mars a series of
experiments were performed to quantify the rate
of evaporation of various brine concentrations
under a simulated Martian atmosphere utilizing
the Andromeda chamber. It was hypothesized that
highly concentrated sulfate brines have the
potential to retain a significant amount of H20
in the polyhydrated state.
Fig. 5 20 Wt MgSO4
Fig. 1 Gendrin et al. (2005)
Fig. 6 25 Wt MgSO4
Fig 3. Dalton et al.
Methods Experiments were performed in the
Andromeda chamber, in a simulated Martian CO2
atmosphere with a constant pressure between 5 and
6 Torr, and temperature of 0C. Brines were
place in petri dishes along with a thermocouple
and placed onto an analytical balance located
within the chamber, Mass loss was measured for
2 hrs for each experiment.
Acknowledgements I would like to thank Julie
Chittenden, Kathryn Bryson, and Walter Graupner
for their immense help in learning to operate the
Andromeda chamber, and Dr. Sears and Dr. Chevrier
for their help and guidance.

• References
• Vaniman D, Bish D, et al. Nature (431)2004..
• 2. Gendrin A, Mangold, N, et al. Science,(307)
  2005.
• 3. Dalton J, et al. Icarus (177) 2005.

Fig. 2 Gendrin et al. (2005)