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Habitable Exomoons

Habitable Exomoons. Rory Barnes with lots of help from René Heller. Habitable Exomoons are Awesome!. Rory Barnes with lots of help from René Heller. What is an exomoon ?. Exomoons !?. You’re gonna talk about habitable exomoons !?. We don’t even understand

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Habitable Exomoons

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  1. Habitable Exomoons Rory Barnes with lots of help from René Heller

  2. Habitable Exomoons are Awesome! Rory Barnes with lots of help from René Heller

  3. What is an exomoon?

  4. Exomoons!? You’re gonna talk about habitable exomoons!? We don’t even understand habitable exoplanets!

  5. The Habitable Zone is about Surface Energy Flux ~300 W/m2 ~30 W/m2

  6. Keplercould find an exomoon.

  7. Keplercould find an exomoon. See the exomoon?

  8. Exomoon Transits and Timing Variations Kipping et al. (2012)

  9. Exomoon Transits and Timing Variations Direct Detection Kipping et al. (2012)

  10. Exomoon Transits and Timing Variations TTV Kipping et al. (2012)

  11. Exomoon Habitability I. Formation A. Inside Circumplanetary Disk B. Capture C. Planet Migration II. Radiation A. Starlight B. Reflected Light C. Planetary Thermal Emission D. Eclipses III. Tidal Heating

  12. The Scale of the Galilean Satellites Callisto 27 RJup Europa 10 RJup Io 6 RJup Ganymede 16 RJup

  13. Canup & Ward (`06) transform disks into moons Total mass of moons ~10-4 of planet Earth = 0.003 Jupiter

  14. Williams, AsBio, submitted

  15. Capture Possibilities Williams, AsBio, submitted

  16. Capture Possibilities Williams, AsBio, submitted

  17. Capture Possibilities Planet has to move to 1 AU! Williams, AsBio, submitted

  18. Planet Satellite Semi-Major Axis (AU) Planetary Semi-Major Axis (AU) Galilean Moons Jupiter’s Radius Time (Years) Namouni (2010)

  19. Instabilities due to planet’s shrinking gravitational influence Satellite Semi-Major Axis (AU) Planetary Semi-Major Axis (AU) Jupiter’s Radius Time (Years) Namouni (2010)

  20. Moons still safe at 1 AU Satellite Semi-Major Axis (AU) Planetary Semi-Major Axis (AU) Jupiter’s Radius Time (Years) Namouni (2010)

  21. Exomoon Formation/Composition May form with planet (<10 Myr) - Icy worlds (volatile rich) - But small May be captured - Requires precise encounters - Captured body must have water - Terrestrial planets need ~100 Myr to form Moon must survive migration to HZ

  22. The Radiation Environment of Exomoons Heller & Barnes (2013)

  23. Starlight Only – The Habitable Zone

  24. Reflected Light – Almost Negligible Multiply your HZ boundary by this factor For F star, outer HZ pushed out by ~0.01 AU at aps < 5 RJup Heller & Barnes (2013)

  25. Reflected Light – Almost Negligible Multiply your HZ boundary by this factor For F star, outer HZ pushed out by ~0.01 AU at aps < 5 RJup There is a “Reflection Correction” for habitable exomoons Heller & Barnes (2013)

  26. Thermal Emission Heat from star (almost negligible) Heat from Contraction (important early) Longitude Heller & Barnes (2013)

  27. Planets Cool with Time* * adopted from Baraffe+ (1997, 2003)

  28. A Moon at Europa’s Orbit Run. Grnhs Limit

  29. Time in a Runaway Greenhouse

  30. Time in a Runaway Greenhouse The moon could lose its water early. There is a “Cooling Edge” for habitable exomoons

  31. Eclipses Longitude Heller & Barnes (2013)

  32. Eclipses No Eclipses Eclipses Stellar radiation dominates With eclipse -> sub-planetary point is cold No eclipse -> sub-planetary point is hot Heller & Barnes (2013)

  33. Radiation The HZ applies Reflection Correction Cooling Edge Eclipses could affect local climate

  34. Tidal Heating Caused by gravitational flexing of the crust Source of tectonics on Io, Europa and Enceladus Could be very large for large moons Could also produce exo-Europas Could sustain plate tectonics indefinitely

  35. Earth orbiting Jupiter orbiting the Sun Tidal Greenhouse Tidal/Radiation Greenhouse Super-Io Tidal Earth No Tidal Heating

  36. Earth orbiting Jupiter orbiting the Sun

  37. Earth orbiting Jupiter orbiting the Sun

  38. Earth orbiting Jupiter orbiting the Sun There is a “Tidal Heating Edge” to exomoon habitability

  39. Conclusions Large exomoons probably rare Kepler can detect, but hard Planets add energy to the classical HZ A reflection correction pushes HZ out (slightly) Thermal radiation causes a cooling edge Eclipses could alter weather A tidal heating edge could sterilize close moons Tidal heating could sustain star-free habitats

  40. For more info: Heller & Barnes, 2013. “Exomoon Habitability constrained by illumination and tidal heating.” AsBio, 13, 18-46.

  41. Tidally Heated to Habitable? Reynolds, McKay & Kasting (1987)

  42. Radiative + Tidal HZs Reynolds, McKay & Kasting (1987)

  43. Orbits After Capture Porter & Grundy (2011)

  44. Reflected and Thermal Light (“inplanation”) Heller & Barnes (2013)

  45. Heller & Barnes (2013)

  46. Heller & Barnes (2013)

  47. Heller & Barnes (2013)

  48. Heller & Barnes (2013)

  49. Heller & Barnes (2013)

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