So, could you have a planet where there was only conditions favorable

Why wouldn't those canyons be filled with water?

Seems pretty plausible.

>>53042969
Evaporated away as the atmosphere buggered off? Never had much water to begin with? Many are, but not all?

>>53042867
They'd have to be pretty deep, but yeah. Read the book Out Of The Silent Planet, thats basically what they do there. There are even ashlander-giants who cross the frigid thin-aired expanses between the canyons by basically cross-country skiing.

>>53043149
This was the first thing I thought of when I read the op. That whole trilogy was pretty good but out of the silent planet was especially good. CS Lewis is an underrated Sci if writer, even if all his books are just catholic allegories.

>>53043306
That Hideous Strength is trash, but OotSP and Perelandra are both amazing.

>>53043327
Perelandra was a little too thinly veiled in the jesus department for me to really love, but it was still great and I love the descriptions of the world and the battle with the satan-analogue.

>>53043382
Sure. I like the sci-fi ideas and the lore, but the book doesnt really have a strong narrative thrust other than "Ima make a space bible". As long as you go in knowing the C.S. Lewis was gaga for christ Id say its required reading for anybody claiming to be into classic sci-fi.

This happens in the Hork-Bajir Chronicles, too.

>>53042969
>>53043027
If the canyons are truly deep enough, perhaps it gets too hot at the bottom and the water evaporates back up again.

>>53042867

That seems plausible. Perhaps the seperate canyons are linked by ancient tunnels left by a progenitor civilization?

>>53042969
i can think of two ideas
>the canyons are wide enough that the water forms into lakes and rivers in the center but there's still plenty of room for people to live
or
>beneath the canyon floors are large underground reservoirs and channels that the water drains into, reemerging as hot springs and steam in areas with a lot of volcanic activity before returning as rain as the clouds rise closer to the cold surface

comic book mini-series by Garth Ennis called Just a Pilgrim.

something about our understanding of solar evolution is a bit off, and the sun begins growing into a red giant much earlier than anyone predicted. most of the former surface of the earth is uninhabitable, but the former seas have mostly evaporated and are now sort of livable, with deeper trenches holding water (and mutants and stuff).

the series may or may not be readable depending on what you're into, but the setting is interesting enough to be worth a look.

https://en.wikipedia.org/wiki/Just_a_Pilgrim

>>53044415
Or perhaps the cliffs aren't completely straight vertical walls, but steep slopes broken by shelves and alcoves everywhere. Plenty of room for life even though the actual bottom is underwater.

>>53045049
>>53044415
Probably both work with geography. Thermal venting to the cold surface also repopulates the ice up there.

File: Desert_Planet.jpg (44KB, 800x600px) Image search: [Google]

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Bump. Maybe we can get a thread on other unusual planetary geographies that are still possible?

Of course, there's terminator worlds, where you live on the twilight line in a tidally-locked planet. Supposedly desert worlds may be more livable than we once thought, albeit mostly at the poles.

>>53042867
You will be best served with a planet smaller than Earth, as well. Think a larger analogue to Mercury, but further away from the parent star and with more water, of course.

A thinner crust around a larger iron core may result in crustal fracturing as the planet cools and shrinks slightly. That will be one possible source of canyons. That said, a planet with a functioning plate tectonic system may not respond in the same way, I'm not totally sure if anyone's done research into how those two factors interact.

Also, it will be to your advantage to have as low gravity as possible while still supporting your chosen variety of life, because the lower the gravity the deeper and more sharply sloped a canyon can be and still remain stable. The African Rift Valley is a pretty damn huge canyon, and quite deep, but the walls generally have a shallow slope from landslides and what not. It will also make it more plausible that the atmosphere is thin higher up, and only viable in the canyons, since a smaller planet has a harder time holding onto volatile gases.

>>53042867
Jinx is sort of what you are describing. Although I think its habitable bands have something to do with weird gravity due to its shape.

>>53047988
What about a planet like Zendikar where mountains just kinda float and move arbitrarily?

>>53049691
Is there even a vague guess as to what the minimum safe gravity for the human body is?

>>53050484
Mars' gravity is probably too low, long-term. But that's long-term as in, permanent colonization from beings not evolved to those standards.

80% of Earth's gravity? You're probably ok, even with human immigrants. Maybe even slightly better than ok, depending on which winds up being better for overall health, lower cardiovascular stress versus heavy gravity properly weighing down on bones.

>>53044829

There was another comic called Sheva's War that had a similar planet.

Basically, the planet's atmosphere was too thin to breathe except in the deep canyons that wound about the planet.

Seems logical enough, but from a geological standpoint one wonders how a planet evolves in such a way.

File: thevalley_large2.jpg (4MB, 4160x5385px) Image search: [Google]

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>>53042867
Well you'd definitely have the basis for creating some interesting stories, like pic related.

This was a setting map made by a Euro anon on Cartographer's guild, with the main idea being a sort of River Nile scenario but with the endless snow surrounding this valley; in the past three sorceror-kings came to power, divided the valley into three parts, and warred with one another until the citizenry rose up in revolt, and their armies turned on them. Now, after a long time of peace the overcrowding of the cities and the demand for wood and metals have combined to start people esploring outside of the valley, something that was near impossible before the advancements of the modern day when it came to equipment and sleds and other tech.

I could imagine your world being sometthing similar, but with different climates in each valley perhaps?

>>53053672
One idea I had was that if some canyons still experienced strong volcanism, than somewhat-higher altitudes might be permanently shrouded in hot, dense fog as water running downhill evaporated before reaching the inhospitable deepest regions.