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Help with small planet?
Topic Started: Jan 31 2010, 11:22 AM (1,014 Views)
KayKay
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Well, I was a bit bored. So I drew a planet on paint:

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The top two images you're looking at either poles, the equator is the circumference of each of the two diagrams. On the smaller four, the equator cuts through the middle of the circles horizontally. The top two (may be incomplete) show a simplified diagram of the tectonic movements on the planet. The middle two show areas of land formation and their direction of formation. The bottom is pretty self-explanatory.

Thing is, I have no idea how plausible it is. If its plausible, I'm not quite sure how it would affect its general orbit and axis, and any oscillations that may occur - I mention that mostly because of the fact that one of the poles has a nearly circular plate that while generally rotating at the same speed as the rest of the planet's crust, it does shake and grind a lot and may jump forward or backwards in the day (by no more than a few minutes bear in mind!) as a result of earthquakes, but still remain a relatively constant speed. This could either be an old temporary feature related to the planet's formation that will not sustain itself for very long, or it could be a constant feature IF possible in a way that can sustain life.

Please point out any areas of error, inconsistency or misunderstanding on my part, it would really help me in the process of revising this idea.

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Empyreon
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Are you plausible?

I like that idea. It can't survive on the limited supply that outgassing would provide, nor should a convenient rain of comets maintain it over billions of years. But some crazy orbit that lets it scoop a supply of air off the parent planet would be really cool, so long as life on the moon can survive the "collision".
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Ànraich
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Well I imagine it would be just a quick pass through the upper atmosphere. I was thinking that maybe it was just close enough to leech off the planet, but I figure that if it was that close it would probably just be sucked in anyways.
We should all aspire to die surrounded by our dearest friends. Just like Julius Caesar.

"The Lord Universe said: 'The same fate I have given to all things from stones to stars, that one day they shall become naught but memories aloft upon the winds of time. From dust all was born, and to dust all shall return.' He then looked upon His greatest creation, life, and pitied them, for unlike stars and stones they would soon learn of this fate and despair in the futility of their own existence. And so the Lord Universe decided to give life two gifts to save them from this despair. The first of these gifts was the soul, that life might more readily accept their fate, and the second was fear, that they might in time learn to avoid it altogether." - Excerpt from a Chanagwan creation myth, Legends and Folklore of the Planet Ghar, collected and published by Yieju Bai'an, explorer from the Celestial Commonwealth of Qonming

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Canis Lupis
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Disclaimer: I'm no planetary physicist, so this may not be the most plausible.


But wouldn't it be better for life on the planet (and for the planet as a whole) if this gas giant had a massive magnetic field that also served as a magnetic field for the planet?
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Parasky
Feb 3 2010, 05:52 PM
Well I imagine it would be just a quick pass through the upper atmosphere. I was thinking that maybe it was just close enough to leech off the planet, but I figure that if it was that close it would probably just be sucked in anyways.
Maybe not, this planet should have more inertia then the gas, so maybe it can pass through at just the right distance where it can grab the gas and run. Though, if it is possible, it would have to thread the needle to just pass through with out hurting it's orbit, let alone just falling in.
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Are you plausible?

Hmm, I wonder if a planet/satellite's Roche limit can be smaller than the planet's radius...

Even if you can figure out an orbit where the moon passes through the planet's atmosphere and not just get sucked in or torn to pieces gravitationally, then there's still the issue of what the experience would be like on the surface. A sudden influx of planetary winds mixing and churning, possibly scouring the surface. Maybe life will have to go underground for the duration of this period?

The outer layer of jovian planets (as far as we've seen) is mostly hydrogen, isn't it? Is that all the moon would be able to scoop up? If so, how can the aliens put a hydrogen atmosphere to use?
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KayKay
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Wait, you're saying a small Earth-like planet can't hold an atmosphere?

As I said, by small I meant Earth-sized, maybe Mars-sized at the absolute smallest.
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Are you plausible?

It's generally accepted that Mars' atmosphere is so thin because a) it has low gravity, and b) it has no magnetosphere, which would protect the planet from the scouring action of solar winds. If your planet is mars-sized let's hope that it either has an atmosphere thick enough to begin with that the scouring isn't a problem, and/or young enough that the solar winds haven't had enough time to really do any damage.

The idea of putting it around a jovian planet might mean that the jovian's own magnetosphere would give it enough protection. I'm not sure. It's probably as likely (if not more so) as setting up a moon with an orbit that can scoop out enough jovian air to maintain an atmosphere.

But it's also important to consider that Venus, being much closer to Earth's size, has no magnetic field either. Maybe magnetosphere generation doesn't have as much to do with planet size as we think...
Edited by Empyreon, Feb 4 2010, 09:21 AM.
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Ànraich
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Venus has a constantly-replenishing atmosphere, so it keeps making atmosphere at a rate equal to or greater than the rate at which it is stripped away.

I forgot you said Earth-sized (when you said small planet I used Earth as the standard for "non-small"). Yea, it could hold an atmosphere, but you either need a magnetosphere or high volcanic activity.
We should all aspire to die surrounded by our dearest friends. Just like Julius Caesar.

"The Lord Universe said: 'The same fate I have given to all things from stones to stars, that one day they shall become naught but memories aloft upon the winds of time. From dust all was born, and to dust all shall return.' He then looked upon His greatest creation, life, and pitied them, for unlike stars and stones they would soon learn of this fate and despair in the futility of their own existence. And so the Lord Universe decided to give life two gifts to save them from this despair. The first of these gifts was the soul, that life might more readily accept their fate, and the second was fear, that they might in time learn to avoid it altogether." - Excerpt from a Chanagwan creation myth, Legends and Folklore of the Planet Ghar, collected and published by Yieju Bai'an, explorer from the Celestial Commonwealth of Qonming

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Are you plausible?

Does Venus replenish from constant outgassing or something?
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T.Neo
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The presence of a planetary magnetic field is determined by the composition of the core and whether it is liquid or not. Venus has no magnetic field due to the fact that it rotates VERY slowly.

Venus's atmosphere seems to be protected somewhat by the ionosphere, so perhaps a magnetic field might not be THAT vital to atmospheric survival. And yes, Venus's atmosphere is replenished by volcanism, as is that of Earth.

You can get bodies much smaller then the Earth that can still hold an atmosphere in the HZ. It might be a bit thinner, but it'll be there.

As for the idea of a moon "scooping up" the atmosphere of a gas giant, it's total nonsense.

For one, the moon would break apart from being within the roche radius (the roche radius will almost always extend past the atmosphere), and even if it could survive that, it would probably disentegrate and deorbit in the atmosphere.

The atmosphere of a gas giant is also mostly hydrogen- stuff I can't see life using. And it's also pretty light, so it would tend to escape faster then oxygen or nitrogen.

A moon being sheltered within the magnetosphere is FAR more plausible. In fact it happens (at least partially) in our own solar system.

A moon having it's own magnetic field is also very possible, if the moon has a warm enough interior and rotates fast enough.

So, yeah. IMO you could get a pretty small habitable moon around as gas giant. But not as small as you have proposed, sorry. :(


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KayKay
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Ok, well I was hoping it wasn't going to be a moon but a planet orbiting a star something like Earth.

Thanks for the extra insight and speculation, and the corrections. I'll be sure to take a note of it when working out specifics. :)
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