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How would a jungle planet work?

Travis

Misanthrope of the Mountains
Travis
Joined
Mar 31, 2007
Messages
24,133
As you know in science fiction single climate planets are pretty much the norm. Now in that context their existence can be attributed to the general laziness of science fiction writers but it got me wondering how they might actually work.

Now a planet that is just one huge cold wasteland is not hard to imagine because we actually have numerous examples right here in our own solar system. But a jungle planet I'm having a hard time with. On Earth jungle plants only exist in a specific region (the tropics) as they need a specific temperature range and lots of available water. So I'm sort of at a loss to figure out how to construct a scenario where jungle plants can be at the equator of a planet and also at the poles. I'm thinking maybe a system with multiple stars but for all of them to be close enough to matter in a thermal sense would make the system unstable for the planet to even be there.

So maybe some sort of hugely scaled air current system that very efficiently transports heat from the tropics to the poles? But even then there would naturally be regions of less precipitation and that would prevent the jungle from taking root as well.

Anyone else got ideas?
 
Technically "Jungle" does mean tropical, but is that what these (unnamed) writers really mean? There are plenty of forests in temperate climates here on earth, and I don't automatically exclude those when I think of a "jungle planet".
 
How about a very large axial tilt with a fairly rapid precession of the axis or rotation?
 
I can think of a few characteristics that might create a jungle planet.

- Land masses that only exist in equatorial regions.

- No plate tectonics.

- No planetary tilt along the axis.

- Long days with a night that doesn't descend into total darkness. Maybe a binary system where only one star is visible in the sky at a time and where the secondary star is significantly further away from the the planet than the main star.

- High atmospheric CO2, and water vapor.
 
Jungles arise in areas of high rainfall, and temperatures high enough to allow trees (or some other large plant) to grow. Thus, we need to look at two conditions: rainfall, and temperatures.

To get world-wide rainfall you need a relatively flat planet. Many deserts on Earth are caused by the rainshadow effect of mountains; if you remove those mountains, rainfall would be much more consistent. The second thing you need is relatively large air circulation cells. Jungles are associated with latitudes where Earth's air currents cause an updraft, which causes condensation (air closer to the ground is generally more moist than higher up), which causes rain. Deserts form in the opposite areas--where air circulation causes downdrafts, bringing drier air down to the ground. Finaly, you need high evaporation rates, as in order for rain to fall you need moisture in the air.

Temperatures are a bit trickier....You don't necessarily need a HOT planet, but you DO need a HOMOGENOUS planet. What I mean is, the reason we have tropics and poles is that our planet isn't that efficient at transfering heat across the planet (well, outside of icehouse events). I'm not sure what it would take to make the planet more thermally homogenous....Any spherical body is going to have the same problem, and while increased total temperatures can help I'm not sure it's going to be enough. I guess one way would be a planet like Venus, which has such thick clouds that heat really doesn't escape. The problem there, obviously, is the lack of photosynthesis, but chemosynthesis may be prefered in such an environment. The other problem is the whole "hot enough to boil lead" thing, though, which is somewhat tricky to work around...

In reality, I highly doubt we'll find too many planets that are all one thing. It's vastly more likely that we'll find planets much like our own--with wildly divergent biomes, ranging from very hot to very cold and from very wet to very dry. Pretty much only a dead rock is homogenous, and Mars shows that even that isn't entirely true.

Could a planet's axis be such that there aren't poles per se? Like a tumbling body?
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Not without completey messing up biology. It takes some hardy organisms to survive the transition from equatorial to polar conditions and vice versa, and not just in terms of temperature. This is more likely to starilize the planet than make jungles.
 
The same way that a pseudo-medieval or barely industrial planet on Star Trek can have one culture with one ruler.

*Waves hands*
 
The planet is pure gold, covered with a thin layer of topsoil and/or shallow oceans. The higher thermal conductivity of gold vs. rock keeps the poles warmer.
 
Would having no axial tilt keep the poles more "temperate"?

How about large oceans at each pole, eliminating the problem completely?

Edit: That's what I get for not refreshing immediately before responding. Sorry about that, Tony.
 
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I wouldn't be too worried about the sunlight, tilt, and temperature. Give the planet a nice thick greenhouse-y atmosphere, that makes the temperature uniform. Give it zero or low polar tilt, that gives you polar regions without a deadly six-month nighttime.

The thing I'm worried about is the relationship between topography and the water budget. If there are oceans, then it's not really a jungle planet in the Endor vein. If there aren't oceans, there's no "buffer" in the water cycle. There has to be just the right amount of rainfall to keep the trees happy, but not 10% more, or it'll run off and form an ocean somewhere. And not 10% less, otherwise the trees will be under water stress, which is not what you want on a jungle planet.

My solution: it's not really a jungle planet, it's a floating carpet of vegetation on a (mostly) ocean planet. The jungle's root system reaches the ocean, which keeps the jungle (and atmosphere) pretty well water-saturated, which can then maintain a water-rich, jungle-friendly environment even on the above-sea-level portions of the planet.
 
The earth hasn't always had polar ice caps. Antarctica was once covered with forests, even with earth's axial tilt.

Steve S
 
I wouldn't be too worried about the sunlight, tilt, and temperature. Give the planet a nice thick greenhouse-y atmosphere, that makes the temperature uniform. Give it zero or low polar tilt, that gives you polar regions without a deadly six-month nighttime.
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How thick and greenhouse-y would it have to be to create thermal homogeneity? And how thick and greenhouse-y would it take to make the planet too hot for life as we know it (a fundamental assumption of this discussion)? If the first is higher than the second, we SHOULD be worried about temperature and its causes.

My solution: it's not really a jungle planet, it's a floating carpet of vegetation on a (mostly) ocean planet. The jungle's root system reaches the ocean, which keeps the jungle (and atmosphere) pretty well water-saturated, which can then maintain a water-rich, jungle-friendly environment even on the above-sea-level portions of the planet.
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Not a bad solution. If you have a hot, moist planet to begin with, then hit it with a big comet (over a period of geologic time, to prevent a huge mass extinction), that'd allow the plants to evolve into floating mats as the water level rises. And if you had the right ocean currents, I could see the planet having relatively constant temperatures (after all, ocean currents did that in the past on Earth). And forests don't have much in the way of nutrients in the ground anyway (they're all in the biosphere), so this won't actually create any insurmountable problems.

I have to take back what I said previously. This solution may well create a planet with a single surface biome. It'd be very unlikely, but I can't see anything preventing it so it's certainly possible.
 
steve s said:
The earth hasn't always had polar ice caps. Antarctica was once covered with forests, even with earth's axial tilt.

Steve S
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Yes, but they were temperate forests if I recall correctly.

Also Antarctica has not always been right at the pole.



About the CO2 idea......would a greenhouse effect that pervasive lead to deserts around the equator at some point? And could it be stable?
 
Travis said:
Yes, but they were temperate forests if I recall correctly.
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What planet is depicted as being tropical jungle over every latitude?

Seriously, that writer is in need of a little creativity and education.
 
ben m said:
I wouldn't be too worried about the sunlight, tilt, and temperature. Give the planet a nice thick greenhouse-y atmosphere, that makes the temperature uniform. Give it zero or low polar tilt, that gives you polar regions without a deadly six-month nighttime.

The thing I'm worried about is the relationship between topography and the water budget. If there are oceans, then it's not really a jungle planet in the Endor vein. If there aren't oceans, there's no "buffer" in the water cycle. There has to be just the right amount of rainfall to keep the trees happy, but not 10% more, or it'll run off and form an ocean somewhere. And not 10% less, otherwise the trees will be under water stress, which is not what you want on a jungle planet.

My solution: it's not really a jungle planet, it's a floating carpet of vegetation on a (mostly) ocean planet. The jungle's root system reaches the ocean, which keeps the jungle (and atmosphere) pretty well water-saturated, which can then maintain a water-rich, jungle-friendly environment even on the above-sea-level portions of the planet.
Click to expand...

This is how Pandora works in Avatar, the continent floats on the ocean, the planet is also located within a binary star system but protected by actually being a moon orbiting a gas giant which shields the moon with it's gravity from having it's atmosphere blown away.
 
Travis said:
Anyone else got ideas?
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Use a very thick atmosphere. The surface temperature on Venus, for example, is extremely uniform - not that you'd have to make it THAT thick, but the thicker you make it, the less variability you'll have. Keep the land mass primarily equatorial as well at you can ignore the polar extremes for convenience. You'd have to turn down the sunlight compared to earth to keep it from overheating, but that's OK for a sci-fi setting.
 
Not a bad solution. If you have a hot, moist planet to begin with, then hit it with a big comet (over a period of geologic time, to prevent a huge mass extinction), that'd allow the plants to evolve into floating mats as the water level rises.
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You could also imagine building it from the oceans up. Start with an Earthlike planet, say. Make the oceans nutrient-rich, but also very turbid, so that photosynthetic species have to compete hard for light. Some sort of kelpy species produces a lilypad-like structure and shades out the deeper aquatic plants. A competitor produces a taller frondy that shades out the lilypads, and everything fights its way taller from there.

Or it can be an Earthlike planet, with both dry land and open ocean, on which the floating-mat species (the surface ones anyway) happen to be the same as the dry-land species. Natural "floating islands" on Earth are made up of ordinary wetland plants (cattails, birch, etc.). A classic "blanket bog" is another environment where very similar, terrestrial plants can cover both a partially-waterlogged highland and a totally-waterlogged lowland.
 
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