Characteristics of Mg2 /Fe2 Sulfate Brines Under Martian Conditions

1
Characteristics of Mg2/Fe2 Sulfate Brines Under
Martian Conditions

• C. Nicholson, V. Chevrier, T. Altheide
• cnichols_at_uark.edu, vchevrie_at_uark.edu
• W.M. Keck Laboratory for Space Simulation,
  Arkansas Center for Space and Planetary Sciences,
  University of Arkansas, Fayetteville, Arkansas
  72701

• Introduction
• MgSO4
• Specific Locals Meridiani Planum, Valles
  Marineris, Margaritifer Sinus, and Terra
  Meridiani1
• Involved in Martian History
• Currently found on Mars in large deposits (5
  of Martian soils)1
• Suggests liquid source of water
• FeSO4
• Specific Locals Meridiani Planum, Gusev Crater3
• Involved in Martian History
• - Also currently found on Mars
• Good comparison to Magnesium because it is also a
  2 ion and makes 7 hydrate
• Evaporation rates are used to determine water
  stability duration

Data
A
B
Figure 7A FeSO4 brine at pressure and
temperature near the beginning of chamber
run Figure 7B FeSO4 brine after completion of
chamber run, also at pressure and temperature
Figure 3 Relative Mass Loss versus Time of
various brine samples

• Results
• Sulfate samples experiences mass loss when
  exposed to 7 mbar of CO2
• Determined evaporation rates of MgSO4 (Fig. 4)
  FeSO4 (Fig. 5) brine solutions at the
  corresponding surface sample temperature
• Both demonstrate an effect of sample
  concentration on the resulting evaporation rates
• Formation of an ice cap slows sublimation process

Figure 4 Evaporation Rate versus Temperature of
MgSO4 brine samples includes calculated
evaporation lines of Water Ice, Liquid Water and
25 wt MgSO4

• Conclusions
• Evaporation rates are much lower than expected gt
  Increased liquid brine stability at lower
  temperatures
• Due to crystallization of hydrates i.e.
  MgSO47H2O,
• Longer residence time of liquid water on Mars

Figure 1 Brine deposit at West Candor Chasma
lighter colored sediment is kieserite
(MgSO41H2O), darker sediment is iron oxides.

• Experimental Methods
• Solutions were prepared of 10, 15, 20, 25 wt
  MgSO4 and 10.9, 13.7, 17.8, and 18.0 wt FeSO4
• Experimental conditions inside Andromeda Chamber
  (Figure 2)
• Atmosphere temperature ranging from -5C to 0C
• 7 mbar CO2 atmosphere
• Relative Humidity (less
• than) 2
• Evaporation rates determined
• (in mm hr-1) from mass loss
• slopes

Figure 5 Evaporation Rate versus Temperature of
FeSO4 brine samples
Figure 8 Burns Cliff in Meridiani Planum large
magnesium sulfate deposit in the sediment layering
References 1 Gendrin, Aline, et al. (2005)
Science 307, p. 1587-1591. 2 Bibring, J.P., et
al. (2007) Science 317, p. 1206-1210. 3 Lane,
Melissa D., et al. (2004) Geophysical Research
Letters 31.
Figure 6 Theoretical Evaporation Rates of
Crystallizing MgSO4 FeSO4 hydrated phases
includes theoretical saturated FeSO4 (18 wt)
MgSO4 (26 wt)
Acknowledgements Thank you Katie Bryson for her
continuous input and contagious enthusiasm, and
Walter Graupner for his technical support.
Figure 2 Andromeda Chamber