Diverse Carbonates in Exoplanet Oceans Promote the Carbon Cycle

Hakim, Kaustubh; Tian, Meng; Bower, Daniel J.; Heng, Kevin (2023). Diverse Carbonates in Exoplanet Oceans Promote the Carbon Cycle. Astrophysical Journal Letters, 942(1), L20. Institute of Physics Publishing IOP 10.3847/2041-8213/aca90c

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Carbonate precipitation in oceans is essential for the carbonate-silicate cycle (inorganic carbon cycle) to maintain temperate climates. By considering the thermodynamics of carbonate chemistry, we demonstrate that the ocean pH decreases by approximately 0.5 for a factor of 10 increase in the atmospheric carbon dioxide content. The upper and lower limits of ocean pH are within 1–4 of each other, where the upper limit is buffered by carbonate precipitation and defines the ocean pH when the carbon cycle operates. If the carbonate compensation depth (CCD) resides above the ocean floor, then carbonate precipitation and the carbon cycle cease to operate. The CCD is deep (>40 km) for high ocean temperature and high atmospheric carbon dioxide content. Key divalent carbonates of magnesium, calcium and iron produce an increasingly wider parameter space of deep CCDs, suggesting that chemical diversity promotes the carbon cycle. The search for life from exoplanets will benefit by including chemically more diverse targets than Earth twins.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Hakim, Kaustubh, Tian, Meng (B), Bower, Daniel James, Heng, Kevin

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics

ISSN:

2041-8205

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Danielle Zemp

Date Deposited:

27 Feb 2023 13:45

Last Modified:

29 Mar 2023 23:38

Publisher DOI:

10.3847/2041-8213/aca90c

BORIS DOI:

10.48350/179289

URI:

https://boris.unibe.ch/id/eprint/179289

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