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Recipe for a Habitable Planet Recipe for a Habitable Planet Aomawa Shields Clare Boothe Luce Associate Professor Shields Center for Exoplanet Climate and Interdisciplinary Education (SCECIE) University of California, Irvine ASU School of Earth and Space Exploration (SESE) December 2, 2020 A moment to pause… Leading effectively during COVID-19 • Employees Need Trust and Compassion: Be Present, Even When You're Distant • Employees Need Stability: Prioritize Wellbeing Amid Disruption • Employees Need Hope: Anchor to Your "True North" From “3 strategies for leading effectively during COVID-19” (https://www.gallup.com/workplace/306503/strategies-leading-effectively-amid-covid.aspx) Hobbies: reading movies, shows knitting mixed media/collage violin tea yoga good restaurants spa days the beach hiking smelling flowers hanging with family BINGO Ill. Niklas Elmehed. Ill. Niklas Elmehed. © Nobel Media. © Nobel Media. RadialVelocity (m/s) Nobel Prize in Physics 2019 Mayor & Queloz 1995 https://exoplanets.nasa.gov/ As of December 2, 2020 Aomawa Shields Recipe for a Habitable World Credit: NASA NNASA’sASA’s KKeplerepler MMissionission TESS Transiting Exoplanet Survey Satellite Credit: NASA-JPL/Caltech Proxima Centauri b Credit: ESO/M. Kornmesser LHS 1140b Credit: ESO TOI 700d Credit: NASA TESS planets in the Earth-sized regime Credit: NASA’s Goddard Space Flight Center Which ones do we follow up on? 20 The Habitable Zone (Kasting et al. 1993, Kopparapu et al. 2013) ) Runaway greenhouse Maximum CO2 greenhouse Stellar Mass (M Mass Stellar Distance from Star (AU) Snowball Earth Many factors can affect planetary habitability Aomawa Shields Recipe for a Habitable World Liquid water Aomawa Shields Recipe for a Habitable World Isotopic Birth Tides Orbit Abundance Environ. Elem. Galactic Abundance Location Impact Flux Orbital SCECIE Composition Evolution & Structure Luminosity Magnetic Dust Eccen. Metallicity Field Minor Oscillations Planets Stellar Rotation Planetary Activity Effects System Orbits Companions Sibling SCECIE Satellites Planets SCECIE Spectral Liquid water Energy Masses Distribution SCECIE Obliquity Radius Planetary Orbit Properties SCECIE Dynamics SCECIE Albedo Surface Temps Rotation Clouds Oblatenes rate SCECIE Outgassing Surface Composition SCECIE Liquids Magnetic Atmosphere Field Surface Credit: After Meadows and Barnes UV Pressure Interior 2018 Shielding Atm. Structure Density Structure Credit: AniaBuckle 1-D Energy Balance Model Global Climate Model (EBM) (GCM) Broadband albedos Two-band albedos (for example – Vis/IR) Weight by host star spectrum EBM needs a separate R-T model to incorporate atmosphere into broadband planetary albedo calculation Based on McGuffie and Henderson-Sellers (2005) Koshland Science Museum Global Climate Model (GCM) (Ex. CCSM4 (Gent et al. 2011), LMD Generic GCM (Hourdin et a. 2006)) Koshland Science Museum Conservation of momentum Mass continuity Conservation of energy (1st law of thermo) Equation of state for the atmosphere PREDICTING FUTURE CLIMATE ON EARTH (Smagorinsky et al. 1965, Manabe et al. 1965, Holloway & Manabe 1971, Manabe & Wetherald 1975) IPCC, 2018: Summary for Policymakers Waterbelt Snowball Earth as refuge for photosynthetic life Abbot et al. 2011 Aomawa Shields Recipe for a Habitable World Warming Early Mars Forget and Pierrehumbert 1997, Colaprete & Toon 2003, Forget et al. 2013, Kitzmann 2016, Wordsworth et al. 2017 Credit: ESA Aomawa Shields Recipe for a Habitable World Forget and Pierrehumbert 1997 Aomawa Shields Recipe for a Habitable World “Eyeball Earth” scenario for Gliese 581 g Pierrehumbert 2011 Habitable climates on Proxima Centauri b Turbet et al. 2016 Starlight Ice-albedo Feedback Courtesy of NASA Aomawa Shields Recipe for a Habitable World M-dwarf planets Image credit: ESO/L. Calçada Aomawa Shields Recipe for a Habitable World Snowball! Noice! M Aomawa Shields Aomawa - dwarf planets exhibit more stable climates in simulations in climates stable more exhibit planets dwarf Warm start Warm Cold Cold start M dwarf planet G dwarf planet F dwarf planet 100 100 100 Warm Start Warm Start Warm Start ) ) Cold Start Cold Start ) Cold Start o o o ( ( 80 80 ( 80 e e e d d d u u u t t t i i i t t t a a 60 60 a 60 L L L e e e n n n i i i L L L 40 40 40 e e e c c c I I I n n n Recipe for a Habitable Habitable World a for Recipe a a 20 20 a 20 e e e M M M 0 0 0 60 70 80 90 100 110 70 80 90 100 110 120 80 90 100 110 120 130 Percent Modern Solar Constant Percent Modern Solar Constant Percent Modern Solar Constant Shields (2014) Shields al.et (2013) Shields al.et ) ) ) K K K ( ( ( e e 300 300 e 300 r r r u u u t t t a a a r r r e e e p p 280 280 p 280 m m m e e e T T T e e 260 260 e 260 c c c a a a f f f r r r u u u S S 240 240 S 240 n n n a a a e e e M M M 220 220 220 l l l a a a b b b o o o l l 200 200 l 200 G G G 60 70 80 90 100 60 70 80 90 100 110 60 70 80 90 100 110 120 Percent Modern Solar Constant Percent Modern Solar Constant Percent Modern Solar Constant Effect holds across multiple possible climate regimes Wolf, Shields+ (2017) Aomawa Shields Recipe for a Habitable World M-dwarf planets Sodium chloride dihydrate (“hydrohalite”) Image credit: ESO/L. Calçada NaCl ·2H2O Aomawa Shields Recipe for a Habitable World Hydrohalite precipitation in sea ice T < -23∘ C Carns et al. 2015 Hydrohalite is highly reflective in the IR Shields and Carns 2018 Aomawa Shields Hydrohalite parameterization matters in the HZ, and climate sensitivity increases as instellation is lowered Shields and Carns 2018 Stronger climate sensitivity to hydrohalite parameterization on synchronously-rotating M-dwarf planets Shields and Carns 2018 Aomawa Shields Trenberth diagram Credit: Kevin Trenberth, John Fasullo and Jeff Kiehl M-dwarf planet 108% 88% 100% G-dwarf planet F-dwarf planet InstellationStarlight (%(% ofof what Modern Earth gets Solar from Constant) the Sun) Shields et al. 2019 F-dwarf planet 29% reflected 14% absorbed 16% reflected Shields et al. 2019 G-dwarf planet 27% 19% reflected absorbed 10% reflected Shields et al. 2019 M-dwarf planet 18% 34% reflected absorbed 7% reflected Shields et al. 2019 F-dwarf planet 29% reflected 14% absorbed 16% reflected Shields et al. 2019 M-dwarf planet 18% 34% reflected absorbed 7% reflected Shields et al. 2019 Surface Albedo Ice Fraction Shields et al. 2019 Difference in Specific Surface Temperature Humidity Shields et al. 2019 1-D Energy Balance Model (EBM) Based on McGuffie and Henderson-Sellers (2005) EBM North and Coakley (1979) Heat Ocean and land Dependence of OLR Planetary response transport temperature gradients on Temperature SMART (Spectral Mapping Atmospheric Radiative Transfer model) Meadows & Crisp, 1997; Crisp 1997 SMART (Spectral Mapping Atmospheric Radiative Transfer model) Meadows & Crisp, 1997; Crisp 1997 1.0 HD128167 (F2V) y t i The Sun (G2V) s 0.8 HD22049 (K2V) n e AD Leo (M3V) d r e 0.6 w o p d e 0.4 z i l a m r 0.2 o N 0.0 0.0 0.5 1.0 1.5 2.0 2.5 Land planets orbiting MWavelength-dwarf (µm) stars 1.0 0.8 snow o 0.6 d e 75% bt land b l A 0.4 50% bt 25% bt 0.2 ocean blue marine ice 0.0 0.0 0.5 1.0 1.5 2.0 2.5 Wavelength (µm) After Shields et al. 2013 Andrew Rushby Planets dominated by land reflect more starlight and have lower surface temperatures than ocean- covered worlds. But, land planets orbiting M stars are still warmer than their counterparts orbiting stars with more visible and UV light Based on Rushby, Shields, and Joshi, The Astrophysical Journal, 2019 Temporal habitability and water loss on eccentric planets Recipe for a Habitable World TOO HOT TOO COLD Eccentricity The Earth Instellation Planets orbiting cooler stars are thawed for Palubski, Shields, and Deitrick, The Astrophysical Journal, 2020 larger fractions of the year ` Recipe for a Habitable World Different land surfaces will have different albedos and resulting effects on the climate of TRAPPIST-1 planets Rushby, Shields, Wolf, et al. ApJ, in review Differences of 50 K across lowest (granite) to highest (calcite) albedo land surface Rushby, Shields, Wolf, et al. ApJ, in review Surface Temperature TRAPPIST-1d most capable of supporting life (with low albedo surface (ex. igneous rock) Rushby, Shields, Wolf, et al. ApJ, in press cross-equatorial energy transport increased for lower-albedo planets Rushby, Shields, Wolf, et al. ApJ, in press Aomawa Shields Recipe for a Habitable World Take –away points • Surface composition affects planetary climate and habitability • Important to incorporate spectral dependence of ice, snow, salt, and land albedos into GCMs • Allows for more realistic assessments of possible climates and habitability of exoplanets Acknowledgments • UCI • National Science Foundation • NASA Habitable Worlds Program • Clare Boothe Luce Foundation • UC President’s Postdoctoral Fellowship Program • Virtual Planetary Laboratory • Collaborators –Eric Agol, Sarah Ballard , Rory Barns, Cecilia Bitz, Regina Carns, Benjamin Charnay, Russell Deitrick, John Johnson , Manoj Joshi, Victoria Meadows, Igor Palubski , Ray Pierrehumbert, Tyler Robinson, Andrew Rushby, Vidya Venkatesan, Eric Wolf Thank you! NASA Ames/JPL-Caltech/Tim Pyle Take –away points • Surface composition affects planetary climate and habitability • Important to incorporate spectral dependence of ice, snow, salt, and land albedos into GCMs • Allows for more realistic assessments of possible climates and habitability of exoplanets M-dwarf planet (synchronous) Shields et al. 2019 Synchronous rotation is possible for Kepler-62f e=0.00 e=0.32 Shields et al.
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