How would a jungle planet work?

[MontagK505]

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.

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.

A common theme is to have a jungle world be a satellite of a gas giant orbiting at a comfortable distance from it's primary. Green house effect keeps the modest heat from the primary star trapped in the atmosphere, while tidal effects pump energy into the core resulting in a hopefully even temperature distribution. The jungle might not spread clear to the poles, but it might be wider than found on earth. (Now what movie did I see this in?)

 

[Travis]

I must say that I'm impressed with the ideas being brought up here.

 

[Denver]

I remember an interesting story called "Mid World", where all the relevant areas (to the story) were gigantic tree forests. Most human life existed in the middle of the trees. Deep down below were the roots, and darkness, and swamps. High above were the tops, and avian creatures and predators.

With forests that big, I don't recall them ever caring about addressing the poles.

 

[dasmiller]

As far as getting good sun everywhere - If the planet was orbiting a red dwarf and had a strong axial tilt, you could have decent sun at least some of the time everywhere on the planet. Terrestrial planets have to be pretty close to red dwarves, leading to very short 'years' (perhaps just a few days long). The danger, of course, is that a planet that close should probably be tidally locked to the star.

Putting it around a gas giant mitigates a lot of those issues; it's okay if it's tidally locked to the gas giant. But then you'd want to have an orbit that was substantially tilted wrt the ecliptic, and that would require even more energy than simply tilting the a solo planet's axis.

In my younger days I had great fun trying to design plausible habitible solar systems. My preferred solution for terrestrial planets was a close-in elliptical orbit around a red dwarf with a 3:2 rotation resonance, much like Mercury has.

But stepping back a bit, I consider "jungle planets" and "desert planets" and their ilk to represent a failure of imagination. I don't know why another planet would have any less variation than Earth does. Even an "ice planet" (which has some historic support) would probably have many very different environments from the perspective of those who live there.

If you really, really want a jungle planet, then I'd suggest that rather than adjusting the planet to support a worldwide jungle, you adjust the jungle to dominate a wide variety of environments. Again, to the locals, there will probably be a tremendous variety in types of jungle, though it may all look like jungle to us.

Last thought on perspective (it didn't quite fit the flow of the above, but I like this paragraph anyway):
From the perspective of a gasbag creature that lives in Jupiter's cryo-winds, there's not much difference between a terrestrial jungle and a terrestrial conifer forest. From the perspective of a *big* gasbag creature, the difference between a terrestrial rain forest and a terrestrial desert would be that one has a green film on the surface and the other has a brown film.

 

[MattusMaximus]

This whole thread has reminded me of Pyrrus, the "Deathworld" from Harry Harrison's stories

 

[Tony]

Edit: That's what I get for not refreshing immediately before responding. Sorry about that, Tony.

No worries bro.

Thinking about this further, I realize that a planet without plate tectonics would almost certainly be flattened and turned into a global ocean by erosion. So there would need to be plate tectonics, but the movement would have to be slow enough for erosion to keep mountains from getting too large (thus preventing the mountain from creating a rain shadow desert), but fast enough to keep erosion from completely washing all the rock and dirt into the ocean.

 

[Travis]

Well, you see all those planets will have their own Noah's Flood so they don't even need plate tectonics.

 

[dasmiller]

This whole thread has reminded me of Pyrrus, the "Deathworld" from Harry Harrison's stories

Another one that seemed to me to be a failure of imagination . . .
<sigh>
But Spaceship Medic was one of the first SF books I read, way back when, and it got me to try the rest of the field. So I'll always give Harry the benefit fo the doubt

 

[rjh01]

How about a 90 degree tilt? Yes you would have half year of darkness. During that time everything could hibernate. This includes the trees. They might lose their leaves like many trees here do.

The other idea is to have two suns. The planet is in one of the L points so that the suns are at fixed points in the sky. Sort of. Then combine that with a 90 degree tilt and there is only a small season of night-time.

 

[theprestige]

I know that if you get rid of trees, you get rid of the familiar "jungle planet" trope pretty much entirely, but why does it have to be trees? And oceans?

Why not some sort of fungal colony, as a substrate for diverse ecosystems? A vast, planet-covering network of linked growths, mediating the planetary resources for the various biomes and niche organisms that inhabit its vast expanses?

Deep roots, tapping crust and mantle for vitamins, minerals, and even energy. Vast cysts, enclosing the waters of seven seas. Acres of leafy outgrowths, filtering atmospheric gases and converting sunlight to work. Fronds and flagellae, pores and sphincters, recycling biomass wherever it may be found. Not so much "jungle", more like "shoggoth-as-garden".

 

[Soapy Sam]

That most certainly is not how Pandora works.

You have forgotten the scene where they visit the Na'vi who live on the plains.

Pandora is not covered entirely in jungle.

And the Naavi "Fisher tribes" didn't seem troubled by the sort of tides I'd expect with a primary that big and close.
Re the OP- Look at the cold / temperate rainforest of the Pacific North West. That's as "jungly" as anything in Brazil or Africa. Early explorers had hell trying to get through it.
I'd simply expect a jungle planet to have different types of tree forming the primary canopy at different latitudes.
I don't know that the Gondwanan Glossopteris forests were "jungles", but certainly a vast, circum (S) polar forest belt.

 

[Halfcentaur]

That most certainly is not how Pandora works.

You have forgotten the scene where they visit the Na'vi who live on the plains.

Pandora is not covered entirely in jungle.

Call of the hounds with your most certainty's. I never said it was a forest planet, there are massive oceans and a number of other ecosystems not visited in the movie. None the less, in the background encyclopedia the forest continent floats around as a mat of vegetation, rather than plate tectonics the entire planet has a behavior similar to this I recall. I was only remarking upon the similar idea to the floating mass as it seemed an interesting topic not often visited in science fiction.

 

[Halfcentaur]

The gravity is also noticeably less than the planet Earth's since Pandora is smaller, which is why so many of the life forms developed six appendages rather than four, for improved traction.

 

[Roboramma]

The gravity is also noticeably less than the planet Earth's since Pandora is smaller, which is why so many of the life forms developed six appendages rather than four, for improved traction.

Really? That sucks.

I'm pretty sure that the prevalence of four limbs on tetrapods is an evolutionary accident. We all descended from four limbed creatures, and it's simply not easy to evolve new limbs. [Edit: losing limbs, on the other hand, may be easier]

When I saw the movie I thought it was really cool that they showed how evolution could unfold differently but with the same mechanisms: on this world it happened that these life-forms underwent an adaptive radiation from an original six limbed ancestor, but those six limbs were adapted to many new niches.

Evolution is contingent, and I thought that the biology shown in the movies was exceptional in it's ability to include that concept: it struck me as a very well thought out view of how earth-like life could evolve on an alien world. If they really did mean it as "six limbs get more traction in this low gravity environment", well, that, to me, is much less impressive.

 

[Halfcentaur]

Alas, this is what the background info says, which is considerably large. There are 4 limbs animals as well as six, but the reason you see so many six limbed animals is due to a fluke that was highly successful. But the background information has many different examples, as I said it is surprisingly large.

Everything from the formation of the planet to how it's atmosphere developed to how it's life forms evolved is chronicled. It's actually fascinating to see how ten years or so of sitting around not making a movie produced so much background. What's amusing to me is how much a friend of mine makes an issue that alien life is too similar to Earth in science fiction, and he used this point to make the exact opposite case to yours.

 

[Roboramma]

What's amusing to me is how much a friend of mine makes an issue that alien life is too similar to Earth in science fiction, and he used this point to make the exact opposite case to yours.

I agree with him that "alien life is too similar to Earth in science fiction", but could you spell out the "exact opposite case" that he made? I'd be interested in hearing it.

I actually thought Avatar did a great job of presenting alien life as different from life on Earth, but still subject to evolutionary forces: it still came about by the same processes, but under different conditions and its outcomes were contingent upon different events. That was actually, for me, one of the best things about the film.

Edit: I was willing to suspend disbelief on the similarity of Naavi to humans as a necessary part of making an entertaining movie.

 

[Soapy Sam]

I can't help feeling there was also quite a bit of contingent pinching of ideas from various SF writers. The Naavi look a lot like C.J.Cherryh's Atevi to me, apart from the colour.

But, I too liked the evolutionary aspects of the movie. The problem with truly alien aliens is that a human audience is unlikely to empathise with them. Had the Naavi looked like giant bugs, communication with the fictional humans would have been even less mutually informative than in the movie and the audience would have been right behind the Colonel. Trudi and the rest would look like traitors.
Compare "Avatar" and "Starship Troopers".

ETA But we're flirting with topic drift, here.

 

[JJM 777]

JWs and other Biblical literalists have a theory how the earth had a temperate climate everywhere before the, ehm, flood.

 

[Toke]

I remember an interesting story called "Mid World", where all the relevant areas (to the story) were gigantic tree forests. Most human life existed in the middle of the trees. Deep down below were the roots, and darkness, and swamps. High above were the tops, and avian creatures and predators.

With forests that big, I don't recall them ever caring about addressing the poles.

I read one with the concept of "Stories" in the jungle, humans lived in a specific type on "home" tree with their symbiotic "bears"
Traveling too many stories up or down got them into very dangerous territory.

This whole thread has reminded me of Pyrrus, the "Deathworld" from Harry Harrison's stories

All you need is for the jungle to be sentient/emphatic and react with violent evolution of plants and animals to human fear/hostility.

I see not problem with a jungle world where the nature of the inpenetrable forest change with temperature zone. (We kind of live on one.)

 

[catsmate]

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.

I like this! An interesting addition to my Traveller universe.