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 habitable exoplanets!

The Habitable Zone is about Surface Energy Flux

~300 W/m2

~30 W/m2

Kepler could find an exomoon.

Kepler could find an exomoon.

See the exomoon?

Exomoon Transits and Timing Variations

Kipping et al. (2012)

Exomoon Transits and Timing Variations

Direct Detection Kipping et al. (2012)

Exomoon Transits and Timing Variations

TTV

Kipping et al. (2012)

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

The Scale of the Galilean Satellites Europa 10 RJup

Io 6 RJup

Callisto 27 RJup

Ganymede 16 RJup

Canup & Ward (`06) transform disks into moons

Total mass of moons ~10-4 of planet Earth = 0.003 Jupiter

Williams, AsBio, submitted

Capture Possibilities

Williams, AsBio, submitted

Capture Possibilities

Williams, AsBio, submitted

Capture Possibilities

Planet has to move to 1 AU!

Williams, AsBio, submitted

Planetary Semi-Major Axis (AU)

Jupiter’s Radius

Time (Years)

Satellite Semi-Major Axis (AU)

Galilean Moons

Namouni (2010)

Jupiter’s Radius

Time (Years)

Satellite Semi-Major Axis (AU)

Planetary Semi-Major Axis (AU)

Instabilities due to planet’s shrinking gravitational influence

Namouni (2010)

Jupiter’s Radius

Time (Years)

Satellite Semi-Major Axis (AU)

Planetary Semi-Major Axis (AU)

Moons still safe at 1 AU

Namouni (2010)

Exomoon Formation/Composition May form with planet ( sub-planetary point is cold No eclipse -> sub-planetary point is hot Heller & Barnes (2013)

Radiation

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

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

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

Earth orbiting Jupiter orbiting the Sun

Earth orbiting Jupiter orbiting the Sun

Earth orbiting Jupiter orbiting the Sun

There is a “Tidal Heating Edge” to exomoon habitability

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

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

Tidally Heated to Habitable?

Reynolds, McKay & Kasting (1987)

Radiative + Tidal HZs

Reynolds, McKay & Kasting (1987)

Orbits After Capture

Porter & Grundy (2011)

Reflected and Thermal Light (“inplanation”)

Heller & Barnes (2013)

Heller & Barnes (2013)

Heller & Barnes (2013)

Heller & Barnes (2013)

Heller & Barnes (2013)

Heller & Barnes (2013)

Heller & Barnes (2013)