geochemistry of carbon cycles on rocky exoplanetsgeochemistry of carbon cycles on rocky exoplanets...

Geochemistry of Carbon Cycles on Rocky Exoplanets Kaustubh Hakim 1 , Dan J. Bower 1 , Meng Tian 1 , Russell Deitrick 1 , Pierre Auclair-Desrotour 1 , Daniel Kitzmann 1 , Caroline Dorn 2 , Klaus Mezger 3 , Kevin Heng 1 A Lithology-based Silicate Weathering Framework 1 University of Bern, Center for Space and Habitability, Gesellschaftsstrasse 6, 3012 Bern, Switzerland 2 University of Zürich, Institute for Computational Science, Winterthurerstrasse 190, 8057 Zürich, Switzerland 3 University of Bern, Institute of Geology, Baltzerstrasse 1+3, 3012 Bern, Switzerland WHY? • The long-term carbon cycle (carbonate-silicate cycle) provides the essential negative feedback in maintaining temperate climates on Earth [1]* • Silicate rocks on exoplanets are likely to be diverse than present-day continents • Previous studies model the sensitivity of weathering rates on the partial pressure of carbon dioxide ! "# $ using reaction rate coefficients based on chemical kinetics Weathering rate ∝ ! "# $ % [1] • Example weathering reaction: • Equilibrium chemistry also allows determining & [2] @exokaustubh [email protected] http://www.exokaustubh.com WHAT? KEY FEATURES • Estimates of weathering from first principles of chemistry • Applicable to both seafloor and continental silicate weathering HOW? • We track the total dissolved inorganic carbon at chemical equilibrium (DIC *+ ) DIC *+ = CO . /+ + [CO 2 .3 ] + [HCO 2 3 ] HIGHLIGHTS • The sensitivity (& ) of the weathering feedback to ! "# $ is not constant as assumed by previous studies • It is a strong function of lithology and ! "# $ • Our framework is based on geochemical reactions and extendable to non- silicate weathering and atmospheres denser or more dilute than that of Earth References [1] Walker, Hays & Kasting (1981), J. Geophys. Res., 86, 9776 [2] Winnick & Maher (2018) EPSL 485, 111-120 *Other references are omitted for clarity of this presentation Illustration credit: Jenny Leibundgut CaSiO 3(s) + 2 CO 2(aq) +H 2 O ↔ Ca 2+ + 2 HCO 3 – + SiO 2(aq) © Authors. All rights reserved

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GeochemistryofCarbonCyclesonRockyExoplanets

KaustubhHakim1,DanJ.Bower1, MengTian1,RussellDeitrick1,PierreAuclair-Desrotour1,DanielKitzmann1, CarolineDorn2, KlausMezger3, KevinHeng1

ALithology-basedSilicateWeatheringFramework

1 UniversityofBern,CenterforSpaceandHabitability,Gesellschaftsstrasse 6,3012Bern,Switzerland2 UniversityofZurich,InstituteforComputationalScience,Winterthurerstrasse 190,8057Zurich,Switzerland

3 UniversityofBern,InstituteofGeology,Baltzerstrasse 1+3,3012Bern,Switzerland

WHY?• Thelong-termcarboncycle(carbonate-silicatecycle)providestheessentialnegativefeedbackinmaintainingtemperateclimatesonEarth[1]*

• Silicaterocksonexoplanetsarelikelytobediversethanpresent-daycontinents

• Previousstudiesmodelthesensitivityofweatheringratesonthepartialpressureofcarbondioxide!"#$ usingreactionratecoefficientsbasedonchemicalkinetics

Weatheringrate∝ !"#$% [1]

• Exampleweatheringreaction:

• Equilibriumchemistryalsoallowsdetermining& [2]

@exokaustubh

[email protected]

http://www.exokaustubh.com

WHAT?

KEYFEATURES• Estimatesofweatheringfromfirstprinciplesofchemistry

• Applicabletobothseafloorandcontinentalsilicateweathering

HOW?• Wetrackthetotaldissolvedinorganiccarbonatchemicalequilibrium(DIC*+)DIC*+ = CO. /+ + [CO2.3] + [HCO23]

HIGHLIGHTS• Thesensitivity(&)oftheweatheringfeedbackto!"#$ isnotconstantasassumedbypreviousstudies

• Itisastrongfunctionoflithologyand!"#$

• Ourframeworkisbasedongeochemicalreactionsandextendabletonon-silicateweatheringandatmospheresdenserormoredilutethanthatofEarth

References[1]Walker,Hays&Kasting (1981),J.Geophys.Res.,86,9776[2]Winnick&Maher(2018)EPSL485,111-120*OtherreferencesareomittedforclarityofthispresentationIllustrationcredit:JennyLeibundgut

CaSiO3(s) +2CO2(aq) +H2O↔Ca2+ +2HCO3– +SiO2(aq)

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