Life on moons?

You might get more answers in the Science Fact subforum of the Science Fiction Forum.

The short answer is yes it is possible, just not in our solar system unless by habitable you include pressurized domiciles of some sort. If you want a breathable atmosphere, your gas giant would have to be much closer to the star than Jupiter, or your star would have to be much brighter than Sol. Your moon would probably have rather harsh extremes of summer and winter, unless maybe it had a rapid orbit around the gas giant.

Yes, there could be life in gas giant moons. A possibility proposed by scientists is a gas giant orbiting a red dwarf. I found some links for you:
http://en.wikipedia.org/wiki/Aurelia_and_Blue_Moon
http://news.sciencemag.org/sciencenow/2011/06/does-life-exist-on-distant-moons.html
http://www.space.com/7709-moons-avatar-pandora.html

I don't see why two moons couldn't contain life. A catastrophic event like a giant eruption or a meteor collision could have sent rocks with unicellular life into space. Some of these rocks would be trapped by the still-barren planet's gravity, seeding life there. In this case, lifeforms would share a common biochemical structure, but evolve in wildly different directions.

Absolutely. There is no rule that says moons need to be barren and with no atmosphere. Many of them are geologically active and Titan even has an atmosphere as well as lakes (or carbon) on the surface. A lot of scientists say Titan is a (methane-based) example of Earth a few billion years ago.

So really as long as it's in the habitable zone of the star (and not orbiting a planet with a really strong magnetic field) then absolutely it could develop complex life and be a nice place to live


There's also nothing preventing a second moon from being habitable as well.

The most likely place to find life in our solar system is on Europa, a moon of Jupiter.

It's covered in liquid water beneath an ice crust and many scientists suspect there could be anything from microbial life to actual creatures in its seas.

Our findings of deep, deep sea life in climates that weren't believed to be able to support life changed the ideas about what could exist in dark waters a while ago.

There has been talk off and on about sending a sub but NASA's funding is... not robust. It's really what scientists are excited about in the looking for nearby actual life category though.

As to whether a moon surrounding a gaseous planet in another system (so it'd presumably be warmer) could support human life without tons of technology? Sure, why not? A moon is often a piece of the larger planet that was knocked off. They're not necessarily anything in particular. Can have water, different environments.

Yes, there would be lunar eclipses, but they don't have to be so frequent nor last so long as to be a problem. Space is BIG, and even something as large as a gas giant won't be exactly between its moons and the sun for more than a few Earth hours.

Now, day duration is interesting. Moons always show the same side to the planets they are orbiting around. They don't spin in place. This means their day/night cycle is as long as it takes for them to complete their orbit around the planet. One day in our moon lasts one lunar month, or roughly 28 Earth days, but other moons orbit much faster. A day/night cycle that lasts 2 to 7 Earth days is realistic, and could have interesting effects on fauna and flora.

Since the planet wouldn't seem to move in the sky, it would be an ideal reference for navigation in the hemisphere where it is visible.

sciencewarrior said:

Now, day duration is interesting. Moons always show the same side to the planets they are orbiting around. They don't spin in place.

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Wait, wait, I've always heard they do rotate or they wouldn't always show the same face always. . . are you sure?

Moons can spin relative to their parent planets in just the same way that planets spin relative to their suns. It's just that most of the ones we can see don't. Eventually, the various forces in play slow the rotation and the two become tidally locked (Wikipedia's article on tidal locking explains it fairly well, with handy diagrams). This does technically happen with any pair of orbiting bodies, but with stars and planets the distances are usually huge enough that the gravitational gradient is minimal and therefore the tidal effects are too small to cause tidal locking. Planets and their moons have much greater tidal interactions, and the moons of gas giants are particularly affected because of the gas giant's strong gravity. Theoretically, a young moon (astronomically speaking, so "only" a couple of billion years) may not be tidally locked yet and would therefore rotate relative to its parent planet. Again, the Wikipedia article helps here - the tidal locking timescale formula that I remember from my orbital mechanics lectures is given in the article.

roseangel said:

Wait, wait, I've always heard they do rotate or they wouldn't always show the same face always. . . are you sure?

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You're right. That was what I was trying to say, but it's hard to explain this stuff without pictures. In general, any moon old enough to contain oceans, life, and a breathable atmosphere will be tidally locked; it will rotate as fast as it orbits the planet, and no faster.

Speaking of tides, if you have several moons with a significant mass orbiting the gas giant, you may end up with very complex tide patterns. Figuring them out could be a full-time job.