View Full Version : Life on moons?

08-07-2012, 05:57 PM
Is there anyone out there who could tell me if a moon surrounding a gas giant could ever be a habitable environment for humans?
And if yes, would this be possible for more than one moon of the same gas giant?

I found it quite difficult to get information about moons as habitable environments in particular, so if anyone knows a book or webpage where I could find something about this topic I'd also be happy :)

08-07-2012, 06:22 PM
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.

08-07-2012, 06:43 PM
The question was not meant to be restricted to our solar system, but to any place of the universe and any kind of solar system in general.
With "habitable environment for humans", to clearify that, I mean a place where humans (or other mammals, or other animals from a somewhat higher evolutionary stage, meaning: not just bacteria, protozoon, or such) could potentially survive without the use of technology.

I've thought about posting it in the scifi subforum, but then thought as it's a more general kind of question it might be better to ask here. Not sure, though.

08-07-2012, 07:07 PM
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:

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.

08-08-2012, 09:04 AM
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.

08-08-2012, 09:32 AM
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.

08-09-2012, 04:17 PM
I was just wondering if the gas giant the moon (or moons) belongs to wouldn't most likely block it off from the sun for a longer period as the moon is orbiting it? And wouldn't that prevent the evolution of somewhat higher lifeforms?
Alternatively, the moon would have to orbit in a way that the said thing won't happen, but I have no idea about the likelihood of this.

08-09-2012, 05:15 PM
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.

08-10-2012, 12:27 AM
Now, day duration is interesting. Moons always show the same side to the planets they are orbiting around. They don't spin in place.

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

08-10-2012, 01:04 PM
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.

08-10-2012, 02:08 PM
Wait, wait, I've always heard they do rotate or they wouldn't always show the same face always. . . are you sure?

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.

08-13-2012, 03:51 PM
Sciencewarrior, I forgot to say thanks for these links in your first post. Especially the Aurelia and Blue Moon thing was really fascinating, and there's even a documentery about it online.

About the tide patterns - would this be such a significant thing? On earth, for example, you have lots of places you never notice anything about tides, as there's no ocean around.
Would multiple moons have effects that are much more significant than the effects of our moon?
Because if not, I could simply choose to write in a way I don't have to figure them out at all. Let things happen some miles away from the shore.
Then, another thing - if one of these moons consists of nothing but water, what effects would there be?