Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars

Creators: Tutolo, Benjamin M.¹; Hausrath, Elisabeth M.²; Kite, Edwin S.³; Rampe, Elizabeth B.⁴; Bristow, Thomas F.⁵; Downs, Robert T.⁶; Treiman, Allan⁷; Peretyazhko, Tanya S.⁴; Thorpe, Michael T.^{8, 9, 10}; Grotzinger, John P.¹¹; Roberts, Amelie L.¹²; Archer, P. Douglas⁴; Des Marais, David J.⁵; Blake, David F.⁵; Vaniman, David T.¹³; Morrison, Shaunna M.^{14, 15}; Chipera, Steve¹³; Hazen, Robert M.¹⁴; Morris, Richard V.⁴; Tu, Valerie M.⁴; Simpson, Sarah L.⁴; Pandey, Aditi⁴; Yen, Albert¹⁶; Larter, Stephen R.¹; Craig, Patricia¹³; Castle, Nicholas¹³; Ming, Douglas W.⁴; Meusburger, Johannes M.⁵; Fraeman, Abigail A.¹⁶; Burtt, David G.⁹; Franz, Heather B.⁹; Sutter, Brad⁴; Clark, Joanna V.⁴; Rapin, William¹⁷; Bridges, John C.¹⁸; Loche, Matteo¹⁷; Gasda, Patrick¹⁹; Frydenvang, Jens²⁰; Vasavada, Ashwin R.¹⁶

1. University of Calgary
2. University of Nevada, Las Vegas
3. University of Chicago
4. Johnson Space Center
5. Ames Research Center
6. University of Arizona
7. Lunar and Planetary Institute
8. University of Maryland, College Park
9. Solar System Exploration Division, NASA Godard Space Flight Center, Greenbelt, MD, USA.
10. Goddard Space Flight Center
11. California Institute of Technology
12. Imperial College London
13. Planetary Science Institute
14. Carnegie Institution for Science
15. Rutgers, The State University of New Jersey
16. Jet Propulsion Lab
17. Research Institute in Astrophysics and Planetology
18. University of Leicester
19. Los Alamos National Laboratory
20. University of Copenhagen

Abstract

Ancient Mars had surface liquid water and a dense carbon dioxide (CO₂)–rich atmosphere. Such an atmosphere would interact with crustal rocks, potentially leaving a mineralogical record of its presence. We analyzed the composition of an 89-meter stratigraphic section of Gale crater, Mars, using data collected by the Curiosity rover. An iron carbonate mineral, siderite, occurs in abundances of 4.8 to 10.5 weight %, colocated with highly water-soluble salts. We infer that the siderite formed in water-limited conditions, driven by water-rock reactions and evaporation. Comparison with orbital data indicates that similar strata (deposited globally) sequestered the equivalent of 2.6 to 36 millibar of atmospheric CO₂. The presence of iron oxyhydroxides in these deposits indicates that a partially closed carbon cycle on ancient Mars returned some previously sequestered CO₂ to the atmosphere.

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Acknowledgement

Mastcam mosaics were processed by the Mastcam team at Malin Space Science Systems. We thank J. Sneed and D. P. Mayer for help in calculating global stratum volumes. We acknowledge the support of the Jet Propulsion Laboratory engineering and management teams and Mars Science Laboratory science team members who participated in tactical and strategic operations, without whom the data presented here could not have been collected.

Funding

B.M.T. acknowledges funding from the Canadian Space Agency, grant 22EXPMSLCA. E.M.H., E.S.K., and M.T.T. acknowledge funding from NASA grants 80NSSC22K0656 (E.M.H.), 80NSSC22K0731 (E.S.K.), and 80GSFC21M0002 (M.T.T.). T.F.B. acknowledges support for CheMin operations provided by NASA’s Mars Exploration Program. A.L.R. acknowledges funding from the Science and Technology Funding Council of the United Kingdom, grant ST/W507520/1. J.C.B. acknowledges funding from the UK Space Agency. P.G. acknowledges support for ChemCam activities from the NASA Mars Exploration Program, grant R-00727-24-0.2. A portion of this research was carried out by A.Y., A.A.F., and A.R.V. at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA (80NM0018D0004).

Data Availability

The Curiosity data are archived in NASA’s Planetary Data System (PDS). The MastCam images used to produce the drill site mosaics are available from PDS at https://planetarydata.jpl.nasa.gov/img/data/msl/msl_mmm/data_MSLMST. Text lists (.lst) of the constituent images that compose the mosaics are provided at the Astrobiology Habitable Environment Database (AHED) repository (50). The ChemCam spectra are available from PDS at https://pds-geosciences.wustl.edu/msl/msl-m-chemcam-libs-4_5-rdr-v1/mslccm_1xxx/data. Information for extracting the specific spectra used (target name, sol, spacecraft clock identifications), details about analysis locations, and the calculated Euclidian distances are included in the AHED repository (51). The CheMin diffraction data were level 4 data products archived in PDS at https://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr4. We used the .lbl and .csv files containing (in their file names) the following values of the spacecraft clock: Tapo Caparo 730910626, Ubajara 737119969, and Sequoia 751061408. The derived mineral abundances are level 5 data products archived in PDS at https://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr5, with the corresponding spacecraft clock identifications. These data are also archived in the Gale crater Mineralogy and Geochemistry database at https://odr.io/CheMin#/search/display/84/eyJkdF9pZCI6IjQzIn0/1. The SAM EGA data are available in PDS at https://pds-geosciences.wustl.edu/msl/msl-m-sam-2-rdr-l0-v1/mslsam_1xxx/data. We used the level 1b data for samples eid25719 (Tapo Caparo 1), eid25723 (Tapo Caparo 2), eid25729 (Ubajara), eid25743 (Sequoia 1), and eid25746 (Sequoia 2). The modified FULLPAT software used in our CheMin data analysis, the code we used to calculate siderite chemical formulas, and the code we used to calculate sulfate strata volume are archived in the AHED repository (50).

Supplemental Material

Materials and Methods; Supplementary Text; Figs. S1 to 12; Table S1; References (51–122) (PDF).

Data S1 and S2 (ZIP).

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