000006842 001__ 6842
000006842 005__ 20240220094459.0
000006842 037__ $$aPOSTER-2024-0033
000006842 100__ $$aHakim, Kaustubh
000006842 245__ $$aCarbonate Compensation Depth in Exoplanet Oceans and Ocean pH
000006842 260__ $$c2023
000006842 269__ $$c2023-04-23
000006842 520__ $$aThe carbonate-silicate cycle is thought to play a key role in maintaining temperate climates on Earth via continental silicate weathering and seafloor carbonate precipitation. Present-day carbonate precipitation on Earth’s seafloor is mainly attributed to calcium carbonates. However, observations of refractory element ratios in stellar photospheres and planet formation models suggest a large diversity in exoplanet bulk composition and thereby the 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 in exoplanets. 
000006842 594__ $$aNO
000006842 700__ $$aTian, Meng
000006842 700__ $$aBower, Dan J.
000006842 700__ $$aHeng, Kevin
000006842 773__ $$tEuropean Geosciences Union General Assembly, Vienna, Austria
000006842 8560_ $$fkaustubh.hakim@ksb-orb.be
000006842 980__ $$aCPOSTER