15:30 〜 17:00
[PPS05-P16] Carbon dioxide sequestration on Earth and Mars: Potential of carbonates derived from Samail Ophiolite as analogues for Martian atmosphere-hydrosphere interactions
キーワード：ALH84001 Meteorite, Carbonate Minerals, CO2 Sequestration, Mars, Oman Ophiolite, Serpentinization
The difference in climate between Earth and Mars may be due to differences in their atmospheric composition, specifically CO2 levels (Earth = 0.4 mbar; [1], Mars = 1-3 bar; [2]). CO2 sequestration via enhanced weathering of ultramafic rocks is regarded as one of the best strategies to mitigate climate change on Earth [3]. It has been extensively studied that the terrestrial atmospheric CO2 reacts with alkaline H2O to form carbonates for long-term storage [4]. Similar research on Mars relies on rover observations [5] and Martian meteorite analyses [6].
According to a recent estimate, atmospheric CO2 accounts for ~80% of the C-budget in Ca-rich carbonates from Oman [4]. Mars has had a thicker atmosphere since the Noachian era (3.9 Ga), due to Tharsis volcanic activity injecting huge amounts of SO2 [7], with greater CO2 buildup than the modern Martian atmosphere. As a result of cloud formation followed by acidic rain, sulfate-rich (40%) sediments were abundantly formed [8]. The Noachian atmosphere could have been lost to space as a result of a combination of impact erosion and sputtering [9]. The residual CO2 began to form carbonates in dust and soil [10], and trace amounts were also found in Martian meteorites [11]. Discovery of phyllosilicates [12] suggest that the H2O on Mars was not acidic until the Tharsis formation. We attempted to estimate the Martian atmospheric CO2 input in Ca-rich carbonates (age = 3.9 Ga; [13]) in ALH84001 (4.1 Ga; [14]). Distinct carbonate populations have been found in ALH84001 using sequential acid extraction and microprobe analysis [6].
The Martian atmospheric CO2 contribution in Ca-rich carbonates in ALH84001 is calculated using a 2-tracer and 3-component mixing model [15]. The end members, such as Noachian CO2 [16], water [17, 18], Fe-Mg-rich carbonates [6], and weathered carbonates [6], are used in the 3-component mixing model (see Image1). Our calculations show that the Ca-rich carbonates in ALH84001 received half of their C-budget (48 ± 16%) from atmospheric CO2, assuming that they formed after the formation of Fe-Mg-rich carbonates during an aqueous event in early Martian history. Other sources (e.g., DIC) account for the remaining 52 ± 14% of the C-budget in ALH84001 Ca-rich carbonates.
Martian meteorites and terrestrial analogues are useful resources for studying Martian surface and subsurface processes until the samples returned to Earth by a mission linked to the Perseverance rover [19]. The carbonates in ALH84001 [6, 17] and Samail Ophiolite [20, 21] are chemically and isotopically distinct, implying that the latter could be a useful Mars analogue [22]. A detailed examination of these carbonate types (particularly listwaenite) will help us understand the evolution of Martian atmosphere-hydrosphere interactions.
References 1. Clark et al. (2021). Life. 11, 539. 2. Jakosky (2019). Planet. Space. Sci. 175, 52-59. 3. Kelemen et al. (2011). Ann. Rev. Earth Planet. Sci. 39, 545-576. 4. Ali et al. (2021). JGR: Solid Earth. 126, e2020JB0212190. 5. Morris et al. (2010). Science. 329, 421-424. 6. Shaheen et al. (2015). PNAS. 112(2), 336-341. 7. Bullock, Moore. (2007). GRL. 34, 19. 8. Clark et al. (2005). EPSL. 240, 73-94. 9. Brain, Jakosky (1998). JGR: Planets. 103(E10):22689-22694. 10. Ehlmann et al. (2008). Science. 322, 1828-1832. 11. Edwards, Ehlmann (2015). Geology. doi:10.1130/G36983.1. 12. Bibring et al. (2006). Science. 312, 400-404. 13. Borg et al. (1999). Science. 286, 90-94. 14. Lapen et al. (2010). Science. 328(5976), 347–351. 15. Liu et al. (2004). Water Resour. Res. 40, W09401. 16. Mahaffy et al. (2013). Science. 341, 263-265. 17. Eiler et al. (2002). GCA. 66(7), 1285-1303. 18. Leshin et al. (2013). Science. 341(6153), 1238937. 19. Ali et al. (2022). Earth Sci. Res. J. 26(3), 221-230. 20. Nasir et al. (2007). Geochem. 67(3), 213-228. 21. Greenberger et al. (2015). EPSL. 416, 21-34. 22. MacArtney (2018) PhD thesis. 23. Deines et al. (1974). GCA. 38, 1147-1164. 24. Beck et al. (2005). GCA. 69(14), 3493-3503.
According to a recent estimate, atmospheric CO2 accounts for ~80% of the C-budget in Ca-rich carbonates from Oman [4]. Mars has had a thicker atmosphere since the Noachian era (3.9 Ga), due to Tharsis volcanic activity injecting huge amounts of SO2 [7], with greater CO2 buildup than the modern Martian atmosphere. As a result of cloud formation followed by acidic rain, sulfate-rich (40%) sediments were abundantly formed [8]. The Noachian atmosphere could have been lost to space as a result of a combination of impact erosion and sputtering [9]. The residual CO2 began to form carbonates in dust and soil [10], and trace amounts were also found in Martian meteorites [11]. Discovery of phyllosilicates [12] suggest that the H2O on Mars was not acidic until the Tharsis formation. We attempted to estimate the Martian atmospheric CO2 input in Ca-rich carbonates (age = 3.9 Ga; [13]) in ALH84001 (4.1 Ga; [14]). Distinct carbonate populations have been found in ALH84001 using sequential acid extraction and microprobe analysis [6].
The Martian atmospheric CO2 contribution in Ca-rich carbonates in ALH84001 is calculated using a 2-tracer and 3-component mixing model [15]. The end members, such as Noachian CO2 [16], water [17, 18], Fe-Mg-rich carbonates [6], and weathered carbonates [6], are used in the 3-component mixing model (see Image1). Our calculations show that the Ca-rich carbonates in ALH84001 received half of their C-budget (48 ± 16%) from atmospheric CO2, assuming that they formed after the formation of Fe-Mg-rich carbonates during an aqueous event in early Martian history. Other sources (e.g., DIC) account for the remaining 52 ± 14% of the C-budget in ALH84001 Ca-rich carbonates.
Martian meteorites and terrestrial analogues are useful resources for studying Martian surface and subsurface processes until the samples returned to Earth by a mission linked to the Perseverance rover [19]. The carbonates in ALH84001 [6, 17] and Samail Ophiolite [20, 21] are chemically and isotopically distinct, implying that the latter could be a useful Mars analogue [22]. A detailed examination of these carbonate types (particularly listwaenite) will help us understand the evolution of Martian atmosphere-hydrosphere interactions.
References 1. Clark et al. (2021). Life. 11, 539. 2. Jakosky (2019). Planet. Space. Sci. 175, 52-59. 3. Kelemen et al. (2011). Ann. Rev. Earth Planet. Sci. 39, 545-576. 4. Ali et al. (2021). JGR: Solid Earth. 126, e2020JB0212190. 5. Morris et al. (2010). Science. 329, 421-424. 6. Shaheen et al. (2015). PNAS. 112(2), 336-341. 7. Bullock, Moore. (2007). GRL. 34, 19. 8. Clark et al. (2005). EPSL. 240, 73-94. 9. Brain, Jakosky (1998). JGR: Planets. 103(E10):22689-22694. 10. Ehlmann et al. (2008). Science. 322, 1828-1832. 11. Edwards, Ehlmann (2015). Geology. doi:10.1130/G36983.1. 12. Bibring et al. (2006). Science. 312, 400-404. 13. Borg et al. (1999). Science. 286, 90-94. 14. Lapen et al. (2010). Science. 328(5976), 347–351. 15. Liu et al. (2004). Water Resour. Res. 40, W09401. 16. Mahaffy et al. (2013). Science. 341, 263-265. 17. Eiler et al. (2002). GCA. 66(7), 1285-1303. 18. Leshin et al. (2013). Science. 341(6153), 1238937. 19. Ali et al. (2022). Earth Sci. Res. J. 26(3), 221-230. 20. Nasir et al. (2007). Geochem. 67(3), 213-228. 21. Greenberger et al. (2015). EPSL. 416, 21-34. 22. MacArtney (2018) PhD thesis. 23. Deines et al. (1974). GCA. 38, 1147-1164. 24. Beck et al. (2005). GCA. 69(14), 3493-3503.