Exomoon Habitability Constrained by Illumination and Tidal Heating

Astrobiology Web ^ | Thursday, October 18, 2012 | Source: arXiv.org

[SunkenCiv]

Exomoon Habitability Constrained by Illumination and Tidal Heating -- The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet, and hence experience days much shorter than their orbital period around the star, and have seasons - all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circum-planetary "habitable edge". We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than ten planetary radii, then this could indicate the presence of a habitable moon.

[SunkenCiv]

Extrasolar moons may provide first glimpse of habitable worlds -- Thursday, October 11, 2012 -- [snip] Researchers believe imaging extrasolar moons (exomoons) could offer unprecedented clues to their ability to support life by providing the chemical signatures carried in their light. [/snip]

[SunkenCiv]

• Exomoon habitability constrained by illumination and tidal heating
  Authors: René Heller, Rory Barnes
  (Submitted on 24 Sep 2012)

  Abstract: The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet, and hence experience days much shorter than their orbital period around the star, and have seasons -- all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circum-planetary "habitable edge". We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than ten planetary radii, then this could indicate the presence of a habitable moon.

[cripplecreek]

Considering the number of moons around gas giants in our system, I'd say we've already found the planets where thousands of them orbit.

[SunkenCiv]

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[Ol' Sox]

Whoa. High tide there must be quite something!

[SunkenCiv]

Thanks cripplecreek. Well said. Jupiter and Saturn have, between them, more than 100 moons, most of them just rocks. The exoplanets currently known (more than 2000) are those which have been easiest to spot given the technology available at the time of discovery. Even the new Alpha Centauri B Earth-sized planet was only detected because of its proximity to the star. This suggests that as technology improves, moons in close proximity to known exosolar giants will become easy to spot. So much more will be coming along.

http://tcaa.us/Images/Relative_satellite_sizes.jpg

http://kepler.nasa.gov/images/20120227KeplerBargraph-glry.jpg

http://spaceplace.nasa.gov/review/switch-a-roo/planet_sizes.en.jpg

http://spaceplace.nasa.gov/review/switch-a-roo/sse_planet_sizes.en.jpg

http://rlv.zcache.com/moons_of_our_solar_system_sticker-p217969198979311554envb3_800.jpg

http://astro-observer.com/solarsystem/img/moon_sizes.jpg

http://solarsystem.nasa.gov/images/SS_Moons-browse.jpg

http://astro-observer.com/solarsystem/compare/comparemoons.html

http://science.nasa.gov/astrophysics/focus-areas/exoplanet-exploration/

http://exoplanets.org/

[blueunicorn6]

Exxon moons? Great. Now they own moons. Probably building convenience stores there for the Martians.

[blueunicorn6]

“Free slurpee with any purchase of ten gallons or more of dilithium crystals!”

[blueunicorn6]

“Please turn off all phasers before pumping crystals.”

[blueunicorn6]

“You got any 30weight oil for my warp drive? Better make that winter blend.”

[blueunicorn6]

“Yeah, I know I didn’t buy any fuel, but you got to let me have the key to the bathroom. There’s not another bathroom for 10 light years and the kid will pee his pants.”

[blueunicorn6]

“Listen buddy, every other store in this galaxy has free air. What’re you, a communist or something? The owner’s manual says to keep it inflated at 32 psi.”

[blueunicorn6]

“Whaddya mean you don’t take checks? Every planet in this galaxy takes checks. What do you want me to do now....go out and scoop the dilithium crystals back out of the tank? You do? Do you have a bigger spoon?”

[blueunicorn6]

“I forgot to take the nozzle out of the tank and I drove off. Three Klingon ships went by me pointing at the back of my rig and laughing their behinds off.”

[blueunicorn6]

“Back in the old days, why they’d come out and clean the windshield on your Mercury capsule. That was service, I tell you.”

[douginthearmy]

Good stuff. Although I am excited about discoveries in space I have some trepidation due to the high probability that whatever life we find will either be a virus that kills us all, a parasite that kills us all, or an intelligent species that kills us all.

[mrsmith]

There is no danger to us from advanced alien civilizations:

“Their bureaucracy will destroy them before they can destroy us before our bureaucracy does.”

Have faith in bureaucracies!

[mrsmith]

They mean “surface” habitability apparently.

All moons are habitable if people want to live there.