I was excited to read this today- that NASA’s Kepler has discovered a binary star system orbited by two large planets, one of which lies in the “habitable zone” (the distance from the stars at which water might exist as a liquid). But news articles on this discovery, and several other large planets (which are easier to find then small planets) that have been discovered in their parent star’s habitable zone, are always quick to point out that it’s unlikely that gas giants harbor life. And they rarely mention any possible moons.
Why? Every gas giant in our solar system has multiple moons- and three out of the foor (Jupiter, Saturn, and Neptune) have moons roughly as large or larger than Earth’s moon. Wouldn’t we expect that just about every extrasolar gas giant we see has moons- probably multiple moons- and thus, multiple chances at life, if in the habitable zone? I know we can’t see the moons yet, but why don’t the articles (or the NASA scientists) say that these planets most likely have a whole pile o’ moons?
We just don’t know, as current detection techniques make it impossible to find anything that small. Extrapolating from the solar system is a dangerous business, as it’s a sample size of one, and may not be typical.
(Btw, the article I read about it did mention the possibility of moons.)
Several SF stories are set on worlds that are satellites of the primary star.
In other words, your idea isn’t outrageous.
Really though, we don’t know.
We have a very small baseline from which to extrapolate.
Our wonderful planet’s ecosystem seems to have evolved in concert with the tidal pull of its sister satellite, Luna. We can probably expect the same kind of gravitational interaction between other primaries and satellites in other systems.
One of the big problems is a gas giant’s moons are likely to be tidally locked. Which means their day/night is going to be as long as it takes to orbit the gas giant. Days that last days and nights that last days is going to be a bit more challenging on any possible ecosystem.
Maybe not a show stopper, but at the very least be a bit different from good ole earth. Different doesn’t mean it can’t happen but the further you get from what you know is possible/works the more likely it is that it isn’t possible/doesn’t work.
Certainly an interesting thing to speculate on… for example, Europa’s orbit around Jupiter takes about 3 and a half earth-days. So the “day” and “night” each last a little under 2 earth-days, roughly. I wonder how bright reflected light from Jupiter is, from Europa and the other moons? In fact, I think I’ll start another thread asking this question.
I don’t think that’s really a problem. On Earth, chemoautotrophs almost certainly arose before photoautotrophs, and there are still plenty of ecosystems that don’t rely on sunlight for energy (deep-sea hydrothermal vents and hydrocarbon seeps spring to mind). And there are large areas of tundra/tiaga that get weeks or months of darkness/sunlight depending on the season. Most of the life-harboring volume of Earth (sediments and the deep oceans) is completely dark. Some of their production is subsidized by detritus ultimately derived from phototrophs, but it doesn’t matter to them how long a day is.
I think the radiation would be a bigger problem than being tidally locked. There’s probably moons. Our current models make it highly unlikely for systems to be swept entirely clean, but of course our current models are mostly based on our own system. But the electromagnetic fields of such large planets stir up a hell of a mess all across the spectrum. Even our probes need significant sheilding if they’re not just passing by at a distance. Maybe there’s life, but whatever it uses to store information would need to be a heck of a lot tougher than our genes.
Not to mention when you get a neighborhood that crowded, orbits would tend to be less stable over the long term. And when you’re sitting right next to a giant vaccum cleaner, the stuff it sucks up on a regular basis could mean a longer period of orbital bombardment.
It is theoretically possible to detect them with existing tech, and there’s even two possible candidates Exomoon - Wikipedia. As for why they’re not often mentioned, well weasels hate to speculate without hard data.
Not really on a habitable planet; an atmosphere serves as pretty good radiation shielding. There’s also the likelihood that a habitable planet would have a magnetic field, further shielding it.
Could current earth life survive if we were suddenly orbiting one of the gas giants? In terms of radiation, not sunlight or gravitational forces or stuff like that, how much more, if any, would we receive if we instantly switched places with one of the outer planet moons?
Extrapolating from the solar system would tell us that these giant planets close to their stars don’t exist. Conditions are obviously quite different in these systems than they are in our solar system.