Life on Moons

[Bleuhelmet]

Disclaimer: This thread is just a brainstorm, I know its just a game.

So in the stream we have seen various inhabited or habitable worlds situated on moons orbiting larger planets. The most glorious example being Blorg itself of course. When seeing this I thought of the question weather life is possible on a moon. There are probably several reason to imagine why not, can an atmosphere maintain itself on a smaller body for instance. My biggest ?? was the amount of sunlight. Depending on the orbit of the moon it can be "behind" its parent body for quite some time. This interuption in sunlight might be to long for life to survive the complete darkness and extreme cold?

Gentlemen and Ladies, discus.....

 

[TheBeautifulVoid2]

I wrote about this one, I believe. Could someone please hunt the thread down?

Short answer: Yes, moons can be habitable. If they orbit a long way out then they will be eclipsed by their parent only briefly.

A thick atmosphere will allow the moon to retain enough heat to not freeze during its eclipse.

 

[QueenoftheIsles]

Blorg is also a moon which is the size of Earth... so it isn't quite what I would call "small."

 

[The_Meme_Man]

Heat is more important than sunlight. Tidal effects from a slightly off orbit can generate heat, and if it is just right the wobble of the axis can be consistent and minimal. Unfortunately they have to be near gas giants, and stable gas giants are almost always far from the sun since they form there, resulting in the planet still being cold without help from huge oceans or greenhouse or geothermal activity (preferably the latter, since that helps create water and release nitrogen).

 

[TheBeautifulVoid2]

Unfortunately they have to be near gas giants, and stable gas giants are almost always far from the sun since they form there,

I've got some awesome news for you: we think there's lots of them. I did a quick database search and found 704 confirmed planets which have a semimajor axis of no more than 1 AU (that is, orbit closer than Earth) and which have a mass at least as large as Jupiter. There could be many more.

 

[Yenzen]

I wrote about this one, I believe. Could someone please hunt the thread down?

Short answer: Yes, moons can be habitable. If they orbit a long way out then they will be eclipsed by their parent only briefly.

A thick atmosphere will allow the moon to retain enough heat to not freeze during its eclipse.

You should write one of your diaries about habitability of red dwarf systems and the possibility of eyeballs earths and habitable moons maybe being able to support life even with the low star output. I don't know much about astronomy, but what little I've read was really interesting since they make up such a large portion of the stars in the universe.

I'm kind of interested in how realistic they really are and how we might be able to cope with them.

 

[TheBeautifulVoid2]

You should write one of your diaries about habitability of red dwarf systems, the possibility of eyeballs earths and habitable moons maybe being able to support life even with the low star output.

I live to serve:

Red dwarf systems
"Eyeball planets"
Habitable moons

 

[EuropaCam]

Except worlds close enough to a red dwarf in order to be in it's Goldilocks Zone are probably going to be tidally-locked, with one side always facing the star, which presents serious challenges for life arising there.

Also, I'd imagine that an orbit that close would increase your risk of extinction events from solar flares.

 

[Yenzen]

I live to serve:

Red dwarf systems
"Eyeball planets"
Habitable moons

Ah, I never saw D-34.

 

[The_Meme_Man]

I've got some awesome news for you: we think there's lots of them. I did a quick database search and found 704 confirmed planets which have a semimajor axis of no more than 1 AU (that is, orbit closer than Earth) and which have a mass at least as large as Jupiter. There could be many more.

I said formed. Gas giants can move, and can fly close to the sun after being formed to be locked in a stable orbit. But they don't form near the sun, and no moon will survive the gas giant shifting orbits. Too close to a star, the gas is too hot to be collected into a gas planet, it has to be rock. Out in the outer rings, gas can freeze to be able to collect and form planets which warm up as they gain mass.

 

[TheBeautifulVoid2]

Too close to a star, the gas is too hot to be collected into a gas planet, it has to be rock. Out in the outer rings, gas can freeze to be able to collect and form planets which warm up as they gain mass.

This is entirely true and I agree with you.

 

[ParagonExile]

I said formed. Gas giants can move, and can fly close to the sun after being formed to be locked in a stable orbit. But they don't form near the sun, and no moon will survive the gas giant shifting orbits. Too close to a star, the gas is too hot to be collected into a gas planet, it has to be rock. Out in the outer rings, gas can freeze to be able to collect and form planets which warm up as they gain mass.

Gas giants can form beyond the frost line, then migrate inwards.

Why wouldn't the moons survive the planet shifting orbits? They are gravitationally anchored to it and follow its trajectory.

 

[22Arkantos]

Why wouldn't the moons survive the planet shifting orbits? They are gravitationally anchored to it and follow its trajectory.

Not sure if they had moons at the time, though it seems likely that they did, but all the gas giants of our Solar System did some shuffling about in their time. IIRC, Neptune was originally closer to the Sun than Uranus, but got kicked out to its current orbit when Jupiter and Saturn got into a 2:1 orbital resonance. We think this may have been the cause of the Late Heavy Bombardment.

 

[mrinku]

It's not just the orbital distance from the primary but the inclination from the ecliptic that determines how often the primary eclipses the satellite. That's why we don't get a Lunar eclipse every month. Uranus is our exemplar here - it's moons are basically orbiting sideways in respect to the ecliptic.

As TBV covered in D-34, the moon being tidally locked could be a more of a concern for habitability, though not an automatic deal breaker.

 

[Oscot]

There are probably several reason to imagine why not, can an atmosphere maintain itself on a smaller body for instance. My biggest ?? was the amount of sunlight. Depending on the orbit of the moon it can be "behind" its parent body for quite some time. This interuption in sunlight might be to long for life to survive the complete darkness and extreme cold?

1) There's a moon in this solar system with a thick atmosphere
2) Interrupting the daylight probably makes it EASIER for life to form, to be honest. It's not so much energy you need as it is energy changes.
3) Even if life is harder to get on moons, from the experience of our own solar system there's 8 planets and 100+ moons. So life could be 10 times harder to form on moons and that's still where you'd expect to find most of it.

 

[Reno Lam]

Disclaimer: This thread is just a brainstorm, I know its just a game.

So in the stream we have seen various inhabited or habitable worlds situated on moons orbiting larger planets. The most glorious example being Blorg itself of course. When seeing this I thought of the question weather life is possible on a moon. There are probably several reason to imagine why not, can an atmosphere maintain itself on a smaller body for instance. My biggest ?? was the amount of sunlight. Depending on the orbit of the moon it can be "behind" its parent body for quite some time. This interuption in sunlight might be to long for life to survive the complete darkness and extreme cold?

Gentlemen and Ladies, discus.....

If the moon possesses a suitably thick atmosphere and the orbital period is not too long, then it is reasonable to assume that the greenhouse effect will be able to keep the moon both reasonably warm during the dark period, as well as to distribute the heat in a more-or-less equal manner across the surface. While things might be tough for producers relying on phtosynthesis on worlds with longer nights (but not necessarily), but odds are producers evolved on such a world would have adopted solutions ranging from simple energy storage or can switch to other forms of subsistance when there are prolonged darkness.

For such a world, though, I think there is one factor that is often not taken into account, especially for larger ones orbiting the star in the habitable zone: reflection. If the gas giant in question is large and reflective enough - the latter indicating it having a lot of water, which is good for its moons as @TheBeautifulVoid noted in the awesome astroknowledge series - then its reflection would contribute a significant portion of energy received by the moon in terms of light. Based on some envelope-back calculation, a roughly Jupiter-sized gas giant orbiting around 0.7AU would provide about as much as half of the star itself for a moon orbiting with a period of about 2 day (based on 55 Cancri f - before I messed up the math)!

While the actual number would probably be smaller due to the smaller size of water gas giants - probably about 10% of the sun for 55 Cancri f - it would nonetheless be a significant part of the moon's climate cycles, not to mention the culture of the people living on it. Indeed, if the gas giant is sufficiently bright, the half of the moon facing the gas giant might never have a true night - the reflection makes the night about as bright as an overcast day. I think it would be a rather interesting scenary, probably a dichromatic surface, with the side facing the planet covered with photosynthetic beings.