000006844 001__ 6844
000006844 005__ 20240220094519.0
000006844 037__ $$aPOSTER-2024-0035
000006844 100__ $$aHakim, Kaustubh
000006844 245__ $$aExoplanet Ocean Chemistry in the Presence of Diverse Carbonates
000006844 260__ $$c2023
000006844 269__ $$c2023-07-09
000006844 520__ $$aThe carbonate-silicate cycle is thought to play a key role in planetary habitability. On Earth, continental silicate weathering and carbonate precipitation on the seafloor enable the storage of atmospheric CO2 in carbonates. Present-day carbonate precipitation on Earth’s seafloor is mainly attributed to calcium carbonates. Geological evidence from the late Archean suggests that iron carbonates could have played a role. Observations of refractory element ratios in stellar photospheres and planet formation models suggest a larger diversity in exoplanet bulk composition than in the solar system and thereby their near-surface composition. In this work, we compute exoplanet ocean pH and carbonate compensation depth (CCD). We find that ocean pH exhibits a limited range of values as a function of ocean temperature and partial pressure of CO2, where the limits are given by the absence and presence of carbonates. The CCD increases with ocean temperature and partial pressure of CO2. If the CCD is above the seafloor, the carbonate-silicate cycle ceases to operate and therefore high ocean temperature and partial pressure of CO2 favor the carbonate-silicate cycle. With the help of pure carbonate systems of key divalent elements, we show that magnesium, calcium and iron carbonates produce an increasingly wider parameter space of deep CCDs, suggesting that chemical diversity promotes the carbonate-silicate cycle. This work motivates the inclusion of more chemically diverse targets than Earth twins in the search for life on exoplanets. 
000006844 536__ $$aFED-tWIN STELLA/$$cFED-tWIN STELLA/$$fFED-tWIN STELLA
000006844 594__ $$aNO
000006844 700__ $$aTian, Meng
000006844 700__ $$aBower, Dan J.
000006844 700__ $$aHeng, Kevin
000006844 773__ $$tGoldschmidt Conference, Lyon, France
000006844 8560_ $$fkaustubh.hakim@ksb-orb.be
000006844 980__ $$aCPOSTER