I was wondering about a setting where a moon orbiting a gas giant can sustain human life on its surface, i.e. with nearly identical conditions compared to Earth (e.g. size, gravity, mean temperature, oceans covering at least 70% of the planetary surface, same atmosphere composition, etc.).
The gas giant orbits a star in the habitable zone, so the moon is in the habitable zone too. Also, the moon would be most likely tidally locked to the gas giant, with an orbiting period of nearly 24h in order to have an Earth-like day/night cycle.
Due to this small orbiting period, I guess the moon would be very close to the gas giant, most likely the innermost natural satellite in this system. Additionally, I'm assuming a (nearly) 0° orbital inclination. Because of this, some conditions would be like those of Jupiter's moon Io:
- Stronger tidal forces resulting in intense volcanic activity;
- Stronger magnetic effects, maybe resulting in intense auroras around all the globe;
Additionally, the moon's side facing the gas giant would receive far less light from the sun because of a daily eclipse that would last at least several hours each time. How can this affect life forms development? Could the reflected light from the gas giant replace to some extent the direct sunlight, in order for photosynthesis to work?
Are there any other effects I should account for? If these effects can prevent an Earth-like environment capable of sustaining (human) life, what additional conditions must be met in order to counter them?
Should the gas giant itself have some particular features? I guess that it must be at least comparable to Jupiter in terms of both size and mass, in order to guarantee a stable orbit to its moons.