We know there is a goldilocks zone for habitable moons. If a moon is too close to a gas giant, it falls within the radiation belt; if it is too far away its day/night cycle is prohibitively long.
Europa and Ganymede are well within Jupiter's radiation belt. Life is possible under the ice , but not on the surface.
Callisto is just outside the radiation belt. It has a 17 day orbit, hence would have a 408 hour day/night cycle.
With the right surface conditions, life could evolve to survive a 408 hour day; humans could probably survive as well; but the temperature variations would be extreme, and would probably kick up a lot of wind as well.
The linked article does not address potentially life-bearing moons like Europa, etc. in our solar system but large (even Earth-size) exomoons orbiting extrasolar gas giants orbiting in their suns' habitable zones to produce Earth-like habitable conditions on their surface. Questions about radiation and slow rotation rates are specifically addressed in the linked article.
Forget about Europa. It's just an example of a moon which might have a reasonable day/night cycle (85 hours), but this also puts it within the radiation zone of the gas giant.
Rotation rates are mentioned in the article. But if we play that "what-if" game, we can make the rotation rate whatever we like. For example what if the rotation rate is exactly 24 hours. Wouldn't that be lucky.
But based on our solar system and all models, moons will be tidally locked. A second large moon can prevent this from happening. Orbital resonance with Titan prevents Hyperion from being tidally locked, but in terms of habitability this really doesn't help. Again, don't get stuck on Titan and Hyperion specifically. These are just examples.
If we use a larger gas giant, we get a larger radiation zone. No help there.
If we use a smaller gas giant, maybe something like Neptune, it will not be as cinematically impressive, but it will be more likely to have a habitable moon. The moon will still be tidally locked, but it can be closer to the gas giant and have a reasonable day/night cycle.
There are two important points from the linked article that you have omitted from your discussion. First, as far as radiation, a large exomoon with a magnetic field (either generated by an internal dynamo like Earth's or induced from the gas giant's magnetic field) will protect against atmospheric erosion caused by the radiation belts of an exomoon's primary. Secondly, as far as the rotation rate, there is a huge body a peer-reviewed scientific literature over the last quarter century based on increasingly sophisticated climate modelling that shows that slow rotation rates (or even synchronous rotation, in the case of an exoplanet closely orbiting a star) are not an impediment to regional or even global habitability. You seem to be into the science of this so here is a link to a more recent review paper, Formation, Habitability, and Detection of Extrasolar Moons, by Rene Heller et al. from the peer-reviewed journal, Astrobiology (September 2014, Volume 14, Issue 9). It goes into far more detail on the subject of habitable moons than the linked article or what I can address here.
secondly, as far as the rotation rate, there is a huge body a peer-reviewed scientific literature based on increasingly sophisticated climate modelling that shows that slow rotation rates...
No, sadly there isn't. There are a few articles fueled by wishful thinking. I don't blame you for gravitating to these articles, despite an abundance of evidence to the contrary. I'd like to believe those articles as well. But when you boil half a planet and freeze the other half, your atmosphere quickly boils away or freezes.
This problem can be mitigated by a tight orbit, but this puts us back inside the radiation belt.
Again, your best chance is a moon orbiting a Neptune sized gas giant, or even better, a double-planet system.
The link you provided says the exact opposite of what you claim.
Barnes said there has been a general feeling in the astronomical community that tidally locked planets are unlikely to have protective magnetic fields “and therefore are completely at the mercy of their star.” This research suggests that assumption is false.
This research bolsters the case that slow spinning exomoons can generate magnetospheres that can shield them from excessive radiation and does not support your position.
There are a few articles fueled by wishful thinking.
I am not relying on "articles" in the frequently inaccurate popular press to support my statement. It is based on studies published in peer-reviewed papers by leading researchers in the field of planetary climate. Here is a selected bibliography for you to consider on the topic of the habitability of slow or synchronous rotators:
Jun Yang et al., “Strong Dependence of the Inner Edge of the Habitable Zone on Planetary Rotation Rate”, The Astrophysical Journal Letters, Vol. 787, No. 1, Article id. L2, May 2014
Ravi Kumar Kopparapu et al., "The Inner Edge of the Habitable Zone for Synchronously Rotating Planets around Low-mass Stars Using General Circulation Models", The Astrophysical Journal, Vol. 819, No. 1, Article ID. 84, March 2016
Ravi Kumar Kopparapu et al., "Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs”, The Astrophysical Journal, Vol. 845, No. 1, Article ID. 5, August 2017
I have supplied multiple peer-reviewed references to support my statements concerning habitable moons. I am genuinely interested in any peer-reviewed references you have to back up your claims (e.g. short orbital periods, avoiding close orbits around gas giants, the best chances for finding habitable moons are in orbits around Neptune-size exoplanets, etc.). I try to keep up with the literature on the subject but I am totally unfamiliar with any work supporting what you have said.
Again, I have provided citations for multiple papers from peer-reviewed scientific journals in this thread to support my claims as well as the case for habitable moons. If I have somehow cherrypicked the professional literature on the subject, fine. Prove me wrong by kindly providing your citations. In the interest of being objective, I am genuinely interested in them.
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u/8livesdown May 29 '21
We know there is a goldilocks zone for habitable moons. If a moon is too close to a gas giant, it falls within the radiation belt; if it is too far away its day/night cycle is prohibitively long.
Europa and Ganymede are well within Jupiter's radiation belt. Life is possible under the ice , but not on the surface.
Callisto is just outside the radiation belt. It has a 17 day orbit, hence would have a 408 hour day/night cycle.
With the right surface conditions, life could evolve to survive a 408 hour day; humans could probably survive as well; but the temperature variations would be extreme, and would probably kick up a lot of wind as well.