For the purpose of my story, I need life to be sustainable for two humans. I am willing to completely fudge science to do this, but I thought some Real Science might be nice.
My heroes are on a moon orbiting a gas giant. It is a moon that naturally evolved life, though nothing sentient. Mammals, yes, intelligent life, no. There are forests and lakes and mountains and deserts and it's basically like an alien mini-Earth. Only, it's tidally locked to the gas giant it is orbiting and due to it's orbit, thus experiences 4 weeks of sunlight and 4 of night (with some sunrise/sunset in there). I know that temperatures fluxuate wildly on our moon between daylight and nighttime, but how do you think this can be adapted for a lifesustaining moon?
Do you think the atmosphere would prevent too much cool-off over the night period? What properties do you think plant life my exhibit? Perhaps some sort of "monthly hibernation"? Perhaps all the plants would be some kind of evergreen/conifer adapation? Would it get so cold water would freeze?
Could heat/light/gas/orbit/other moons/something from the planet itself keep the moon from becoming inhospitable during the night periods?
I'm assuming given an appropriate axis tilt, the moon would experience seasons similar to Earth, but how do you think these might work?
I really don't want, "They'd freeze and everything/one would die" type answers. Consider it a challenge to make it work, 'cause my heroes are already there, you know?
Thanks!
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60,041 / 50,000
Nov 23, 2008 - 05 39
I don't remember exactly how he managed it, but Vernor Vinge's A Deepness in the Sky had a star that turned on and off periodically, and there was still life on the orbiting planet. He explained the mechanism quite thoroughly. Might be worth taking a look.
100,043 / 50,000
Nov 23, 2008 - 07 36
In short.. yes, I think it could work.
With a thicker atmosphere you would find that the loss in temperature on the 'night side' is vastly reduced and the differences in temperature between the two (night/day sides) is also not so wide apart as it would be without a reasonable atmosphere.
If you could make the moon's gravity enough so that CO2 didn't escape too quickly, you'd have a nice (mostly) warm moon where plant life, some animals (and microbial life especially) and that kind of thing could thrive. There have been studies into plant life (fossil tree stumps - look up Glossopteris on google/wikipedia) at high latitudes and they are believed to have suffered long dark winters (much as the north/south poles do now). When it is cold, these plants tended to 'shrivel' back to a minimum rhizome (pre-seed/bulb) to conserve energy and reduce their need for sunlight etc.
I formatted my brain after the last exam i had, but I think that's more or less correct.
These pages might help too:
----------Development of life through Earth eras: http://www.fi.edu/fellows/fellow4/nov98/projects/eras.html
Milankovitch cycles: http://www.bbm.me.uk/portsdown/PH_731_Milank.htm
http://en.wikipedia.org/wiki/Tidal_locking
Nano Winner: 2005-2008
Collective word count: 438k
Worst Typoed Sentence: Cannot it wait?" you are a profet of the people
50,475 / 50,000
Nov 23, 2008 - 11 35
Welp... it must have an atmosphere, and atmosphere's moderate things a lot... as well as hold in heat... i mean, if earth was a barren rock, it would probably be 250+ on the sun side and -150 on the dark... (guesses, but not bad ones.)
Still, 4 weeks does mean a lot of baking and a lot of cooling... and there's also the matter of tidal stress to consider, since its in orbit around such a large planet... you may be well off to put it a bit further out into its given solar system, so that if the moon were a small planet by itself it would be frozen over... but given the tidal stress on its core, it has internal heat coming up... THAT way the atmosphere and water can stay moderate, even if the sun is too far away to OVERHEAT the planet, and the 4 week long nights aren't TOO cold because literally half the heat the planet gets is from below rather than above.
Of course, this may make for somewhat 'dim' (say, sunsetlike) days... and since this thing is orbiting a gas giant, even DURING mid-day, the sun will be blotted out for possible a couple days
wholly possible... and, frankly, the moon need be beefy enough and have ozone enough to fend off the GAS GIANT's radiation... but that's also supported by it having a metallic core that is constantly being heated up by said tidal stress.
on top of the aforementioned consequences/possibilities, keep these in mind
- all that tidal stress means more quakes... buildings here will have to be able to handle it
- the terminators (day/night boundaries), given that they are somewhat slow moving, and either side has more time to heat/cool (not to mention the mid-day blackout) this will probably mean heavy storms right along the day-night boundary
these features can add a lot of depth, frankly
50,475 / 50,000
Nov 23, 2008 - 11 41
as far as seasons... hmm
things are a bit complicated... this moons year is effectively 8 week long... so any season it might have would have very little time to have any effect on the environment before they are wiped away by the next season... more or less, your seasons are going to be:
- day (kinda hot, stagnant maybe)
- nightfall (heavy storms, wind, tornados, lightning, etc (which can be present during day, but not even 1/100th as bad)
- night (cool, warm ground, but chill winds, but possibly BRIGHTER than the day (because you are only going to see the sun when you are wrapping around either side of the gas giant and just before you pass behind it for a couple days, at night you are going to be looking right at the full face of the sun-lit gas giant... the light isn't as bright, but it's coming at you from a much larger light source (the distant sun is a pinpoint, while the parent planet is huge in the sky)
- sunrise (more heavy storms)
50,475 / 50,000
Nov 23, 2008 - 11 48
things are a bit complicated... this moons year is effectively 8 week long... so any season it might have would have very little time to have any effect on the environment before they are wiped away by the next season... more or less, your seasons are going to be:
- day (kinda hot, stagnant maybe)
- nightfall (heavy storms, wind, tornados, lightning, etc (which can be present during day, but not even 1/100th as bad)
- night (cool, warm ground, but chill winds, but possibly BRIGHTER than the day (because you are only going to see the sun when you are wrapping around either side of the gas giant and just before you pass behind it for a couple days, at night you are going to be looking right at the full face of the sun-lit gas giant... the light isn't as bright, but it's coming at you from a much larger light source (the distant sun is a pinpoint, while the parent planet is huge in the sky)
- sunrise (more heavy storms)
actually, this depends... what i said
if you are on the gas-giant facing side, the above is true... if you are on the side facing away... than your day will be sun-dominated, and your night pitch black... whereas on the facing side, day is cut in half by a couple days of darkness (usually... if the orbit itself is tilted, then you might skip the short-dark in the middle of the day every other time or so), but the night will be brilliant with the view of the gas giant....
but it's still true... lunar tilt WILL matter, but not nearly as much as it would for earth (the other factors are more aggressive in this moon's case) ...
the things that matter are the orbital tilt (like i said, if its even with planetary orbit around sun, then EVERY day on the planet-side is cut down the middle by a blackout... but if not, then only most will be (this is the reason why OUR moon isn't eclipsed every time it orbits (plus its far away and both it and us are kinda small, so its easier for our shadow to miss it.)) ... but moon tilt... let me think
yes it'll matter.. but really above it's polar circles where day and night can last for several day-years in a row... but given all the internal heat from tidal stress, even these plays may never fully ice over...
(sorry for all the replies, its just i keep realizing new things, and have to come back)
50,105 / 50,000
Nov 23, 2008 - 20 06
No apologies for the replies, they're all excellent and very useful, thank you! Thick atmosphere and the internal issues with the core are perfect and make a lot of sense. My heroes are on the planet-facing side. (I actually did a painting of what I thought it'd look like: http://www.crackerboxpalace.com/art/telsa-5.jpg ) I think there are several moons between this one and the actual gas giant, so it isn't quite as massive/stressed as it would be if it were the same distance from Earth/Luna, etc. I know that the gas giant would always hang in the same place, but it would wax and wane, correct? So presumably sometimes during the nighttime the planet would be "new" and sometimes at nighttime the plante would be "full" and thus give very different light sources on the moon.
I love the ideas of storms on the border for day/night, but why is that? We don't experience storms at sunrise/sunset, so it's hard for me to fathom this.
The moon itself is a fancy-smansy rich tourist resort, but I have it only operating during certain times of the 8-week cycle due to various conditions. The storms and things are a great reason to have it "Closed" for some periods, and it will be good for my heroes, who get trapped there during the cold period when they should have departed.
Given some axis tilt, it makes sense that in a higher altitude or less near the equator they'd experience colder night-weeks.
I'm thinking that the plantlife and animallife will have evolved to adapt to this, either by hibernation or just being able to adust body chemsitry every for weeks--like if a butterfly could go back to being a caterpillar for a while, ahaha. I'll have to think on it.
Thank you for all your help!
53,690 / 50,000
Nov 24, 2008 - 02 57
I love the ideas of storms on the border for day/night, but why is that? We don't experience storms at sunrise/sunset, so it's hard for me to fathom this.
My understanding is that bad weather is caused by cold air masses running into warm air masses. Since your terminator takes four weeks to cross (instead of 24 hours) the sunny side is presumably much warmer than the dark side. So, as the cold (dark) side crosses over the warm (sunny) side, you get turbulence (warm air rises, cold air descends). Mix in some moisture and BOOM, you've got some thunderstorms rolling in.
50,475 / 50,000
Nov 24, 2008 - 08 10
My understanding is that bad weather is caused by cold air masses running into warm air masses. Since your terminator takes four weeks to cross (instead of 24 hours) the sunny side is presumably much warmer than the dark side. So, as the cold (dark) side crosses over the warm (sunny) side, you get turbulence (warm air rises, cold air descends). Mix in some moisture and BOOM, you've got some thunderstorms rolling in.
Exactly!
Still... i did say that this would make more sense if the moon was far enough away from the sun so that it didn't completely bake/chill it (that internal heat was enough to make up for the difference of lack of sun-heat) ... that said it still does move slowly, which makes the temperature on one side different from another... which stirs up weather definitely.
How BAD the weather is certainly debatable... but it would be noticably different from day/night weather
and YUP, the planet would always be in the same place in the sky, but would wane, wax over the course of this moon's day-year.
50,475 / 50,000
Nov 24, 2008 - 08 11
niiice... I wish i'd stuck with art some times... I had potential as a kid, but then discovered 'puters
50,475 / 50,000
Nov 24, 2008 - 08 25
Just be aware that your choice of moon-planet separation is an important part of the equation...
-- get too close, and the moon gets shredded into a ring
-- a bit further out, the thing spills the contents of its mantle up constantly (be it water or sulphur or whatever), like sol jupiter io.
-- a close but stable moon means more the equation can be more about internal heat, and less about sun-heat, which helps calms the weather down, but increases quakes
-- a far but stable moon means more of the equation has to come from heat from the sun, which means less quakes, but more difference between day-night heat, and thus bigger storms at the day/night terminators... warmer days, colder nights
-- too far out and, of course, you get probably a lump of rock and nothing more.
Of course... consider the fact that we're finding super-jupiters out there these days... 5, 10, even 15 times the size... around them, planets the size of earth or larger could very easily be moons... which means not only do they stay hot inside because of tidal stress, but also because, like earth, they are, themselves, heavy... an earth-sized moon around a mega-planet is very plausible and could potentially last much longer than earth can (we only have about a billion years left before we become a big version of mars, for example.) ... but anyways... an earth-sized moon could be quite far from its parent planet and still balance its internal engine for heat with what is provided by tidal stress versus however far away the sun may be.
luck!
50,089 / 50,000
Nov 25, 2008 - 14 11
Give your moon a wet atmosphere with heavy cloud cover. The clouds will reflect heat during the day, keeping the planet from overheating, and water vapor is hundreds of times more powerful a greenhouse gas than carbon dioxide. In addition, water has a very large heat of vaporization, so a lot of your daytime heat goes into making clouds, and during the night, when those clouds rain out, the heat gets released back into the atmosphere to keep things warm.
----------Tanstaafl
23,527 / 50,000
Nov 27, 2008 - 00 38
Whoa, nice.
Remember that the phases of the planet and the moon's day and night are defined by the same sun, and because the moon is tidally locked to the planet and the sun is in the same place for both of them at any given moment, they change in synch. At any given spot on the moon, the planet will always have the same phases at the same time every day. For an observer at the spot on the moon where the planet is directly overhead, the planet will always be full at midnight, and always be new at noon (and probably eclipsing the sun). First quarter at sunset, last quarter at sunrise, always. The exact timing of the phases will vary depending on where on the moon the observer is, but there's nowhere on the planetward side that the planet will ever be new at night, or full during the day.
The temperature differential between the warm day side and the colder night side will generate convection cells that cause constant wind from the night side to the day side at the surface, and from the day side to the night side at high altitudes, as the sun warming air on the day side causes it to rise and flow to the night side to replace air that's cooling, falling, and flowing to the day side to replace the air that's being warmed by the sun and rising...
This is one of the effects that moderates the temperature differences.
Earth gets a bit of this, too, but the differential's much less because the day/night cycle's much shorter, so the heat engine that drives the convection cells isn't as powerful. Earth's big convection cells are oriented north-south because the temperature difference between equator and poles is much more than between day and night at the same latitude.
On the other hand, your moon's slow rotation should mean very little Coriolis Effect, so it should be more straight-line winds than Earth-style rotating storms. (Though take this with a grain of salt... I'm not a xenometeorologist.)
50,727 / 50,000
Nov 28, 2008 - 23 12
don't know if anyone's mentioned it or not, but only one side of your moon has the whole day/night pattern. If it is tidally locked, it means that the same side of the moon is facing the gas giant at all times. Now, Gas Giant's produce light and heat, so that should keep that side of the moon in a constant state of light (probably not as bright as say a sun, but at least lit) and the same constant level of heat bombarding it all the time. The other side of your planet will go through periods of being behind the gas giant from the sun, and being between the gas giant and the sun. You could cheat and use other planets in the system as 'sun blockers' to prevent that side of the planet switching from oven to freezer during these times, or just have a murky upper atmosphere layer so that only so much light gets in, and only so much heat can escape.
The other thing to remember is that we are more protected by our magnetic field than by our atmosphere. If your moon doesn't have a rotating molten layer around the solid metal core like earth does, then immense amounts of radiation from both the planet and the sun.
----------NanoWriMo Efforts:
2006: Crossfire - 57,000 - Success!
2007: Untitled - 33452 - Epic Fail!
2008: Untitled - see for yourself
50,105 / 50,000
Nov 29, 2008 - 19 30
Of course. I am a complete idiot. Fortunately in my novel I actually did it this way, probably subconciously knowing it, but I honestly hadn't thought like that. (Obviously.) So thank you for mentioning it. I am so embarrassed! Ahahaha.
Another sort of related question, I'm realizing that the gas giant would undoubtedly give some tidal force BACK to the moon, right? Obviously any oceans would have waves, but would they be ridiculous? Would smaller bodies of water exibit tidal pull too, like large lakes?
23,527 / 50,000
Nov 29, 2008 - 20 50
Technically, yes, but for practical purposes, no. Because the moon's tidally locked to the gas giant, and always maintains the same orientation towards the gas giant, the tides will be a permanent condition, not a changing thing. Some places will always be at high tide, others will always be at low tide, depending on where on the moon they are relative to the gas giant, and the tide will never rise or fall. Tides that never change are pretty much like no tides at all.
There will be changing tides caused by the sun and by any other moons the gas giant might have. The former will probably be pretty minor; the latter could be both significant and complicated.
50,105 / 50,000
Nov 30, 2008 - 05 01
Technically, yes, but for practical purposes, no. Because the moon's tidally locked to the gas giant, and always maintains the same orientation towards the gas giant, the tides will be a permanent condition, not a changing thing. Some places will always be at high tide, others will always be at low tide, depending on where on the moon they are relative to the gas giant, and the tide will never rise or fall. Tides that never change are pretty much like no tides at all.
There will be changing tides caused by the sun and by any other moons the gas giant might have. The former will probably be pretty minor; the latter could be both significant and complicated.
This all makes so much sense when you say it that it baffles me that I don't just . . .figure it out on my own when I ask. Of course the tides wouldn't change on the facing side and would be much more negligent on the opposite side and vary on the edges. I don't know why I don't realize this myself. I like the ideas of other moons affecting the tide too. It's actually a resort moon, so I can imagine that when an inner moon passes between the planet and my resort moon and the tide gets larger they could be like "SURF'S UP SPECIALS" or something ridiculous. I'm sad I don't have a place to put that in my novel. Next time perhaps.
Thanks for all your help!!