U.S. DEPARTMENT OF ENERGY U.S. DEPARTMENT OF U.S. DEPARTMENT OF ENERGYENERGY U.S. DEPARTMENT OF U.S. DEPARTMENT OF ENERGY ENERGY U.S. DEPARTMENT OF U.S. DEPARTMENT OF ENERGYENERGY U.S. DEPARTMENT OF Atmospheric EscapeENERGY From TOI-700 d: Venus versus Earth Analogs Chuanfei Dong1,2, Meng Jin3,4, Manasvi Lingam5,6 1 Department of Astrophysical Sciences, Princeton University; [email protected] 2 Princeton Plasma Physics Laboratory, Princeton University, [email protected] 3 SETI Institute 4 Lockheed Martin Solar and Astrophysics Lab (LMSAL) 5 Department of Aerospace, Physics and Space Sciences, Florida Tech 6 Institute for Theory and Computation, Harvard University 18th Meeting of the Venus Exploration Analysis Group (VEXAG) Habitable Zone of TOI-700 Green Band: Habitable Zone semimajor axis = 0.163±0.015 AU The first Earth-size planet in its star’s habitable zone discovered by TESS. What will happen when considering the stellar wind and magnetic field? Unmagnetized Venus Magnetized Earth 3 How Does the Sun/Star Affect the Planetary System? Solar Wind Earth-like Magnetized Venus/Mars-like Unmagnetized Exosphere Ionospheric Density Profiles of Venus and Earth Venus Earth Density Peak (O2+) at ~135 km Density Peak (O+)at ~300 km 5 Mendillo et al., 2018 Atmospheric O+ Ion Source and Loss Phi -3 -1 Phi -3 -1 + -3 + -3 RO+ in cm s (early) RO+ in cm s (Carrington) 4 4 4 n(O ) in cm (early) n(O ) in cm (Carrington) 3 3 4 3 Photoionization 2 2 4 4 Z 2 1 1 3 0 0 1 2 2 -1 -1 0 -2 -2 Z 2 -2 Imp-1 0-3 -1 1 2 -2Imp -1 -3 0-1 1 2 RO+ in cm s (early) RO+ in cm s (Carrington) 4 X 4 X 4 0 0 Electron 3Impact Ionization 3 3 1 2 2 -2 -2 Z 2 1 1 0 0 0 1 -2 -1 0 1 2 -2 -1 0 1 2 -1 -1 0 -2 -2 X X -2 CX-1 0-3 -1 1 2 -2CX -1 -3 0-1 1 2 RO+ in cm s (early) RO+ in cm s (Carrington) 4 X 4 X 4 Ancient (4.02 Gyr) solar wind An extreme “Carrington-type” 3 Charge Exchange 3 parameters at 1 au (stellar input space weather event (stellar 3 2 2 from Boesswetter et al. 2010). input from Ngwira et al. 2014) Z 2 1 1 0 0 1 -1 -1 Joule heating included: 0 -2 -2 -2 -1 0 1 2 -2 -1 0 1 2 X X Dong et al., 2017, ApJL; Dong et al., 2019, ApJL Stellar Wind Velocity Stellar Wind Pressure Stellar Wind Density 7 Atmospheric Escape From TOI-700 d (at Pmin): Venus versus Earth Analogs Assuming exoplanets with Venus-like and Earth-like atmospheres orbiting M-type stars instead of solar-type stars. Given the close-in habitable zones of M-type stars, those exoplanets experience higher radiation and particle fluxes than our Venus and Earth. Unmagnetized Venus Unmagnetized Earth Magnetized Earth 2.10×1026 S-1 1.18×1028 S-1 1.39×1027 S-1 8 Dong et al., 2020, ApJL Conclusion • We assess the feasibility of TOI-700 d to retain an atmosphere – one of the chief ingredients for surface habitability – over long timescales by employing state-of-the-art magnetohydrodynamic models to simulate the stellar wind and the associated rates of atmospheric escape. • The simulations show that the unmagnetized TOI-700 d with a 1 bar Earth-like atmosphere could be stripped away rather quickly (< 1 gigayear), while the unmagnetized TOI-700 d with a 1 bar CO2-dominated atmosphere could persist for many billions of years; we find that the magnetized Earth-like case falls in between these two scenarios. • Space weather and stellar wind-induced atmospheric loss need to be taken into account for planetary habitability! Thank You for Your Attention! Traditional Habitable Zones Dong et al., 2018, PNAS Green Band: Habitable Zone.