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

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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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Page 1: Geochemistry of Carbon Cycles on Rocky ExoplanetsGeochemistry of Carbon Cycles on Rocky Exoplanets Kaustubh Hakim1, Dan J. Bower1,Meng Tian1, Russell Deitrick1, Pierre Auclair-Desrotour1,

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)

© Authors. All rights reserved