Experimental MethodsExperimental 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 -5°C to 0°C

7 mbar CO2 atmosphere

Relative Humidity (less

than) 2%

Evaporation rates determined

(in mm hr-1) from mass loss

slopes

Characteristics of Mg2+/Fe2+ Sulfate Brines Under Martian Conditions

C. Nicholson, V. Chevrier, T. Altheidecnichols@uark.edu, vchevrie@uark.edu

W.M. Keck Laboratory for Space Simulation, Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, Arkansas 72701

IntroductionIntroduction

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

ConclusionsConclusions

Evaporation rates are much lower than expected => Increased liquid brine stability at lower temperatures

Due to crystallization of hydrates: i.e. MgSO4·7H2O, …Longer residence time of liquid water on Mars

DataData

ResultsResults

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 2: Andromeda Chamber

Figure 3: Relative Mass Loss versus Time of

various brine samples

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

Figure 5: Evaporation Rate versus Temperature of FeSO4

brine samples

AcknowledgementsAcknowledgements

Thank you Katie Bryson for her continuous input and contagious enthusiasm, and Walter Graupner for his technical support.

ReferencesReferences[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 8: Burn’s Cliff in Meridiani Planum; large magnesium sulfate deposit in the sediment layering

Figure 1: Brine deposit at West Candor Chasma; lighter colored sediment is kieserite (MgSO4·1H2O), darker sediment is iron oxides.

Figure 6: Theoretical Evaporation Rates of Crystallizing MgSO4 & FeSO4 hydrated phases; includes theoretical saturated FeSO4 (18 wt%) & MgSO4 (26 wt%)

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

A B

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

268.00 269.00 270.00 271.00 272.00 273.00

Temperation (K)

Eva

po

rati

on

Rat

e (m

m h

r-1

)

18.0 wt%

13.7 wt%

10.9 wt%

17.8 wt%

Liquid Water

Water Ice

Vac.Sys

Coolant

Insulation

Hygrometer

Platform

Hoist

Lid

Cooling coils

Sampling ports

Thermocouples

Balance

Dry Ice

Thermocouple 1 m