The Climates of Other Worlds: Searching for the Next Habitable Planet
Aomawa Shields Clare Boothe Luce Assistant Professor Shields Center for Exoplanet Climate and Interdisciplinary Education (SCECIE) University of California, Irvine
KITP Friends May 15, 2019
Credit: NASA Radial Velocity (m/s) Velocity Radial
Mayor & Queloz 1995 Phase We are in the Earth-sized regime
Credit: NASA Credits: NASA Ames / W. Stenzel; Princeton University / T. Morton NASA’s Kepler Mission Transit Technique
Credit: NASA Spitzer TESS Transiting Exoplanet Survey Satellite Credit: George Ricker TESS will identify the best and smallest exoplanet targets for characterization of atmospheres James Webb Space Telescope
Starlight filters through the planet’s absorption line spectrum atmosphere
Credit: Northrop Grumman • Habitable planet
• hosting life? Proxima Centauri b
Credit: ESO/M. Kornmesser Credit: NASA-JPL/Caltech LHS 1140b
Credit: ESO Which ones do we follow up on?
16 Contact (1997) New era, new approach • Observational data AND computer models
NASA +
Koshland Science Museum Life’s Requirements
A Liquid (H2O) Bioessential Elements (SPONCH) Energy (Stellar or chemical)
Photo: Frans La
Aomawa Shields The Climates of Other Worlds The Habitable Zone
) Runaway greenhouse
Maximum CO2 greenhouse Stellar Mass (M
Distance from Star (AU) Snowball Earth Many factors can affect planetary habitability Aomawa Shields The Climates of Other Worlds Galactic Location Composition & Structure
Stellar Effects
Spectral Liquid water Energy Distribution Planetary Properties Dynamics
Surface
Atmosphere Interior
Aomawa Shields The Climates of Other Worlds Galactic Location Orbital Composition Evolution & Structure
Stellar Planetary Effects System Sibling Planets Spectral Liquid water Energy Distribution Planetary Properties Dynamics
Surface
Atmosphere Credit: Victoria Interior Meadows
Aomawa Shields The Climates of Other Worlds Isotopic Birth Tides Orbit Abundance Environ. Elem. Galactic Abundance Location Impact Flux Orbital Composition Evolution & Structure Luminosity Magnetic Dust Eccen. Metallicity Field Minor Oscillations Planets Stellar Rotation Planetary Activity Effects System Orbits
Companions Sibling Satellites Planets Spectral Liquid water Energy Masses Distribution Obliquity Radius Planetary Orbit Properties Dynamics Albedo Surface Temps Rotation Clouds Oblatenes rate Outgassing Surface Composition Liquids Magnetic Atmosphere Field Surface Credit: Victoria UV Pressure Interior Meadows Shielding Atm. Structure Density Aomawa Shields Structure The Climates of Other Worlds . 1-D line-by-line radiative transfer models Models . 1-D in height . Atmospheric gas absorption
. Radiative convective climate models
. Energy Balance Models (EBMs) . 0-D or 1-D (in latitude) usually
. 3-D General Circulation Models (GCMs) . Sophisticated treatment of atmospheric circulation, ocean- atmosphere processes Aomawa Shields The Climates of Other Worlds PREDICTING FUTURE CLIMATE ON EARTH IPCC, 2018: Summary for Policymakers Snowball Earth Artist concept
Exploring thaw criteria for Snowball Earth
Abbot and Pierrehumbert 2010
Aomawa Shields The Climates of Other Worlds Abbot et al. 2011
Aomawa Shields The Climates of Other Worlds
Warming Early Mars
Credit: ESA
Aomawa Shields The Climates of Other Worlds Forget and Pierrehumbert 1997 Credit: Spitzer Space Telescope
Aomawa Shields The Climates of Other Worlds Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team
Aomawa Shields The Climates of Other Worlds
Aomawa Shields The Climates of Other Worlds M-dwarf planets
Image credit: ESO/L. Calçada Aomawa Shields The Climates of Other Worlds Red dwarf Sun The Sun
Stellar
Brightness 100% Small planets are easier to detect around small stars small around detect to easier are planets Small G Dwarf M Dwarf Credit: Victoria Meadows Credit: Victoria The Habitable Zone ) Stellar Mass (M
Distance from Star (AU) Snowball Earth
Aomawa Shields The Climates of Other Worlds Synchronous rotation and surface pressure (Joshi, Haberle, and Reynolds 1997)
Host star
Aomawa Shields The Climates of Other Worlds Synchronous rotation can be a benefit for climate and habitability (Yang et al. 2013)
Night side Night side Day side
Credit: Jun Yang Aomawa Shields The Climates of Other Worlds Aomawa Shields The Climates of Other Worlds M-dwarf planets could lose oceans during PMS phase
(Luger and Barnes 2015)
Aomawa Shields The Climates of Other Worlds
Starlight BINGO Aomawa Shields The Climates of Other Worlds Ice-albedo Feedback Courtesy of NASA Shutterstock Photo: Stephen Warren Ice Ice
Photo courtesy of Stephen Warren
Shields et al. (2013) Ice absorbs where M-dwarfs emit strongly Warren et al. (2002) Grenfell et al. (1994) No ice! PAL (“present
atm level”) CO2
Snowball!
Instellation (% of what Earth receives)
M-dwarf planets less susceptible to snowball Shields et al. (2013) F-dwarf planets more susceptible to snowball Aomawa Shields The Climates of Other Worlds M-dwarf planet is more stable against convection
Shields et al. (2013) Albedo Surface Temperature
G-dwarf planet (100%)
M-dwarf planet (90%)
Shields et al. (2013)
Climate Stability No ice!
Warm start
Cold start
Snowball! Shorter jump in ice line Higher jump in ice line Shields et al. (2014) M-dwarf planets have Better for life? more stable climates
Aomawa Shields The Climates of Other Worlds http://sparce.evac.ou.edu/q_and_a/air_circulation.htm, SPaRCE Transports heat from equator to higher latitudes Aomawa Shields The Climates of Other Worlds Hadley circulation on deglaciating planets Northern hemisphere winter
) 645 × 109 kg/s 623 × 109 kg/s 489 × 109 kg/s mb Pressure ( Pressure
Latitude Shields et al. (2014)
Weaker Hadley circulation helps M-dwarf planet thaw more easily
Aomawa Shields The Climates of Other Worlds Identifying Multiple Possible Climate Regimes
Wolf, Shields+ (2017)
Aomawa Shields The Climates of Other Worlds Sodium chloride dihydrate (“hydrohalite”)
NaCl ·2H2O
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 Targeted planet studies
Aomawa Shields The Climates of Other Worlds “Eyeball Earth” scenario for Gliese 581 g
Pierrehumbert 2011 Multiple-planet systems
First place to look for a habitable, Earth-like planet?
Aomawa Shields The Climates of Other Worlds Image credit: NASA Ames/JPL-Caltech
? Too hot
Aomawa Shields The Climates of Other Worlds Kepler-62f
Needs CO2
Aomawa Shields Image credit: NASA Ames/JPLThe-Caltech Climates of Other Worlds Stable eccentricities
e_fmax = 0.32
stable Stable ecc for Kepler-62f 0.00 ≤ e ≤ 0.32
unstable
Shields et al. (2016a) Aomawa Shields The Climates of Other Worlds Surface Temperature
High
CO2
Earth- Open water like axial tilt Shields et al. Circular 2016a orbit Global mean surface temps similar to Earth! Aomawa Shields The Climates of Other Worlds Insolation
PAL CO2
Shields et al. 2016a
Aomawa Shields The Climates of Other Worlds Surface Temperature freezing freezing point point Obliquity = 60° Obliquity = 23°
Shields et al. (2016a) Southern hemisphere summer
Aomawa Shields The Climates of Other Worlds Shields et al. (2016a) Surface Temperature 3 bar CO2
Shields et al. (2016a) Aomawa Shields The Climates of Other Worlds Credit: NASA/JPL-Caltech Courtesy of ESO/L. Calçada Credit: Ansel Adams Take away point Combining observations AND theory = How we will most accurately assess planetary habitability
Aomawa Shields The Climates of Other Worlds Rising Stargirls More than the eye can see
IRAS
Axel Mellinger www.risingstargirls.org Acknowledgments • UCI • KITP • 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, , John Johnson , Manoj Joshi, Victoria Meadows, Igor Palubski , Ray Pierrehumbert, Tyler Robinson, Andrew Rushby Thank you!
NASA Ames/JPL-Caltech/Tim Pyle Email: [email protected] Aomawa Shields Website: http://faculty.sites.uci.edu/shields/ Minimum land fraction for glaciations increases with redder host star SED
Andrew Rushby
Rushby et al. in prep M-dwarf planets G-dwarf planets
Igor Palubski
Palubski et al. in prep Planets orbiting cooler stars are thawed for larger fractions of the year for lower eccentricities NEW WORK (Here at KITP) “Trenberth diagram”
Synchronous rotation is possible
e=0.00 e=0.32
Shields et al. (2016a)