Space: Desert Planets

[whswhs]

Originally Posted by Flyndaran

Deserts are defined as getting fewer than 10 inches of rainfall a year, I believe. I feel people here define it as hot and dry.
The problem is that truly dry regions on earth like the heart of the Atacama, where rain hasn't fallen for centuries, there is zero life, not even lichen or native bacteria.
If you want a true desert planet with water based life, then you need to throw realism out the window entirely.

How did we get from "less than 250 mm" to "zero"?

[Flyndaran]

Originally Posted by whswhs

How did we get from "less than 250 mm" to "zero"?

Depends on what one means when they say, "Desert Planet". Usually it means no oceans, but maybe a few lakes.
You can have life only so far from bodies of water rendering most of the planet dead.

[Nymdok]

Originally Posted by whswhs

How did we get from "less than 250 mm" to "zero"?

I think this is at the crux of it. A really small amount of rain with a little 'life finds a way' optimism could lead to something that is at least 'plausible' depending on your tastes.

Arrakis (didnt read the books, just saw the movies) DID have water, just not enough to qualify as 'alot' on a global scale. But it WAS enough to keep the fremen alive and even at the end of the movie have a nice rainstorm.

One of the areas you might explore for 'wiggle room' in building a desert planet is abandon the idea of a completely oceanless world. If venus, for example, DID have (signifigant) water (and of course a different atmosphere), the oceans would be shallow and I would think more subject to larger temperature swings and maybe even enhanced cloud production that could carry enough rain over a desert landscape to still qualify as a desert AND support life.

So in your pursuit of a Desert world, consider a spectrum of systems from the Atacama to the Sonoran and I think you might be suprised what you could come up with. Dont think of JUST the barren arrakin landscape, but think of one that has that as a large component but maybe also fragile arid ice caps, thin cranky oceans, and in spots even cactus type plants and tumbleweeds with Gorn like creatures existing quite comfortably.

Now Anthony IS right about Water going hand in hand with what we consider liveable mostly due to the large amounts of Oxygen needed to make water, but its not absolutely the case. Consider again, Venus, which technically has more oxygen (in the form of CO2) in its atmosphere than Earth does! (About 100 times as much!) And yet, due to other reasons, there is little water.

Nymdok

p.s. Please note that I dont have the planet building rules from GURPS Im just trying to throw out ideas.
p.p.s. Please also note that Im a firm believer that with enough explanation, almost anything can be plausible.

[Nymdok]

Originally Posted by Flyndaran

Depends on what one means when they say, "Desert Planet". Usually it means no oceans, but maybe a few lakes.
You can have life only so far from bodies of water rendering most of the planet dead.

Well, a hotter planet would have a more vigorous atmosphere I would think which might stretch the range of rain clouds and allow for more spotty lakes?

Nymdok

[ericthered]

Originally Posted by Flyndaran

Deserts are defined as getting fewer than 10 inches of rainfall a year, I believe. I feel people here define it as hot and dry.
The problem is that truly dry regions on earth like the heart of the Atacama, where rain hasn't fallen for centuries, there is zero life, not even lichen or native bacteria.

link? I'm looking for info on this, and no finding any...

[Flyndaran]

Originally Posted by ericthered

link? I'm looking for info on this, and no finding any...

The Atacama desert has a region that haven't had detectable rainfall for up to 400 years. I've read that it's so dry chemically, it works for testing Martian rovers and study.

[ericthered]

Originally Posted by Flyndaran

The Atacama desert has a region that haven't had detectable rainfall for up to 400 years. I've read that it's so dry chemically, it works for testing Martian rovers and study.

And yet a place on earth without bacteria -- all the literature I'm reading says they HAVE found life in the driest parts of the Atacama-- though they say it lives in rock pores, not the soil.

[Flyndaran]

Originally Posted by ericthered

And yet a place on earth without bacteria -- all the literature I'm reading says they HAVE found life in the driest parts of the Atacama-- though they say it lives in rock pores, not the soil.

It's been a while, so I may have missed things or over-generalized what I read.
I thought that even the chemistry of the soil was incompatible with common life from such long periods of dessication.

[jason taylor]

It is a side note, but while we're on single binome worlds how come we don't have a Planatary Romance that takes place on a Mountain Planet.

OK there is Avalon but that is not a single binome world, and doesn't even have that high of mountains, even if much of it does focus there(it is really the West Coast and Cascades Recycled in Space which makes sense as Anderson was a Californian if I recall).

Aeneas in Day of their Return, by the way, was an arid world but it was no Arrakis.

[Flyndaran]

A planet dominated by mountains would have to be very young and/or horribly tectonically active.