CO2 Solubility in Primitive Martian Basalts Similar to Yamato 980459 and the Evolution of the Martian AtmosphereBen D. Stanley1, Douglas R. Schaub2, and Marc M. Hirschmann1

1 Dept. of Earth Sciences, University of Minnesota, 2 Dept. of Geology, Colgate University (stan0525@umn.edu)

P21A-1651

Introduction Experiments FTIR Analysis Conclusions

Previous Work

AGU Fall Meeting 2011

3-11

0 1 2

-10

-9

-8

-7

-6

Pressure (GPa)

golfO

2

Martian Mantle

WI

1+WI

2+WI

3+WI CO Stable2

Graphite Stable

Oxybarometry of SNC meteorites suggests that the oxygen fu-gacity of much of the Martian mantle is reducing (iron-wustite, IW, ±1) and so carbon is likely stored as graphite in a reduced Martian mantle (After [1]).

Data

There is considerable evidence that liquid water was stable on the ancient Martian surface during at least some parts of the late Noachian and early Hesperian epochs. Yet there remains considerable uncertainty as to how this greenhouse was created and maintained and how it evolved to the current thin, modern atmosphere.

Compositions are calculated Cr and FeS-free and normalized.Humphrey - [6]; Y 980459 - [7]; Experimental Humphrey and Y 980459 - electron microprobe analysis of experimental glass

Oxide Humphrey ExperimentalHumphrey Y 980459 Experimental

Y 980459

SiO2 46.96 46.91 49.61 51.59TiO2 0.56 0.53 0.51 0.49Al2O3 10.93 10.52 5.70 6.12FeOT 19.23 19.87 16.75 14.31

MnO 0.42 0.38 0.03 0.45MgO 10.65 10.79 19.08 18.80CaO 8.02 7.99 6.86 7.23Na2O 2.56 2.40 0.65 0.65K2O 0.10 0.11 0.02 0.02P2O5 0.57 0.52 0.30 0.34Total 100.00 100.00 100.00 100.00

melt

2 mm

Pt-Fe doped 400

300

200

100

Abs

orba

nce

(cm

-1)

5000 4000 3000 2000

Wavenumber (cm-1)

CO32-

OH-

CO2 concentration44.01

4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0Time (Ga)

0.001

0.01

0.1

1

10

Cum

ulat

ive

CO

2 Out

gass

ed (b

ar)

IW

IW+1

IW+1

IW

[4]

[4] [5]

Y 980459 source region Gusev basalt source region

Strong Greenhouse

Calculations

C1graphite

+ O2gas

↔ CO2gas

⇒ KI =fCO2fO2

CO2gas

+ O12−

melt↔ CO3

2−

melt⇒ KII =

XCO 3

2−

melt

XO2−

melt fCO2

where XO2−

melt = 1− XCO 3

2−

melt

XCO 3

2−

melt =KIKIIfO2

1+ KIKIIfO2at constant T and P

Holloway et al. [8] showed that the solubility of CO2 in graphite saturated melts is only related to fO2.

XCO3

2 −melt

Experimental CO2 solubilities from [2] were used to fit lnKII allowing calculation of at any P-T-fO2 condi-tions.

The CO2 solubility of synthetic Martian basalts based on the Hum-phrey Adirondack-class basalt showed that degassing of CO2 may not be sufficient to create greenhouse conditions [2]. However, solu-bilities are predicted to be greater for depolymerized melts similar to Y 980459 [3], possibly allowing degassing of increased amounts of dissolved CO2 and a significant contribution of volcanogenic CO2 to an early Martian greenhouse.

In memory of the Spirit Rover01/04/04-03/22/10

Thanks for the rock analyses!

References

AcknowledgementsSupport for Douglas R. Schaub came form the University of Minnesota’s Re-search Experience for Undergraduate program funded by the National Sci-ence Foundation. The NASA Mars Fundamental Research Program funds this experimental program. Electron microprobe analyses were carried out at the Electron Microprobe Laboratory, Dept. of Geology and Geophysics, Uni-versity of Minnesota. Parts of this work were carried out in the Institute of Technology Characterization Facility, UMN, which receives partial support from National Science Foundation through the National Nanotechnology In-frastructure Network program.

[1] Hirschmann M.M. and Withers A.C. (2008) Earth Planet. Sc. Lett., 270, 147-155. [2] Stanley B.D. et al. (2011) Geochim. Cosmochim. Acta, 75, 5987-6003. [3] Brooker R.A. et al. (2001) Chem. Geol., 174, 225-239. [4] Pepin R.O. (1994) Icarus, 111, 289-304. [5] Manning C.V. et al. (2006) Icarus, 180, 38-59. [6] Gellert R. et al. (2006) J. Geophys. Res.-Planet., 111, E02S05. [7] Musselwhite D.S. et al. (2006) Meteorit. Planet. Sci., 41, 1271-1290. [8] Holloway J.R. et al. (1992) Eur. J. Mineral., 4, 105-114. [9] Pan V. et al. (1991) Geochim. Cosmochim. Acta, 55, 1587-1595.

lnKII = lnKII0 −

ΔV0

RT

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟ (P − P0 ) −

ΔH0

R

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

1

T−

1

T0

⎛

⎝ ⎜

⎞

⎠ ⎟

2.0

1.5

1.0

0.5

0

CO

2 S

olub

ility

(wt.%

)160015001400

Temperature (°C)

Y 980459 Humphrey [2]

2.0 GPaa)

2.5

2.0

1.5

1.0

0.5

0

CO

2 S

olub

ility

(wt.%

)

3210Pressure (GPa)

b) Humphrey [2] - 1500 ºC Y 980459 - 1600 ºC Y 980459 - 1625 ºC

Experiments were performed using a 0.5” piston-cylinder apparatus.

The 2 mm Pt capsules were iron-presaturated to prevent Fe-loss.

Conditions: 1600-1650 °C, 1.0-2.0 GPa, and a duration of 30 min.

1.0

0.8

0.6

0.4

0.2

0.0

Cum

ulat

ive

CO

2 O

utga

ssed

(bar

)

4035302520MgO+FeO (wt.%)

Hawaiian tholeiite IW+1 [9] Hawaiian tholeiite IW [9] Humphrey IW+1 [2] Humphrey IW [2] Y 980459 IW+1 (this study) Y 980459 IW (this study) Y 980459 IW+1 (calc) [2] Y 980459 IW (calc) [2]

t = 3.5 Ga

• Experimentally-determined solubility of syn-thetic shergottite basalts confirm that the Martian mantle is incapable of degassing sufficient CO2 to sustain a thick greenhouse atmosphere in the Late Noachian.

• Models of Martian atmospheric evolution using only CO2 should be reexamined and additional volatiles such as SO2 and CH4 should be consid-ered.

• There is little effect of composition on CO2 solubility in Martian basalts.

• NBO/T is an imperfect predictor of CO2 solu-bility in MgO-rich silicate melts.

20

15

10

5

0

CO

2 so

lubi

lity

(wt.%

)

2.52.01.51.00.50

NBO/T (Fe3+ and Fe

2+ network forming)

MM

(31.

5)

Kim (35.8)

Di (25.9)

W47 (25.8)

OM1 (17.2)

0 = -18.0 ± 10.2 kJ mol-1Δ

-18.6

-18.5

-18.4

-18.3

-18.2

-18.1

-18.0

lnK

II

6005805605405201/Temperature (x10-6

K-1)

lnKII0 = -15.4 ± 0.20 = 20.9 ± 0.9 cm3 mol-1Δ

-19.0

-18.5

-18.0

-17.5

-17.0

-16.5

lnK

II

3.02.52.01.51.00.5Pressure (GPa)

5

00.500.250

HOxHRe

Y(1

9.1)

5

00.500.250

HOxHRe

Y(1

9.1)