How to get really deep depresion on an exoplanet?

In summary: The only minor drawback:Cretaceous–Paleogene extinction event left Chicxulub crater, which is 180 km wide.
  • #1
Czcibor
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I want an exoplanet/exomoon with really deep depression. It would be the only place on that planet that's really habitable for humans without breating aid.

Idea:
-lower gravity (somewhere around 0.8 g) so the mountains should be able to be a bit taller
-one supercontinent that's slowly spliting,
-in the middle of the supercontinent near a tropic (dry place) a depression, which get's water from a river starting in mountains
-a continental lake (like Baikal, but one size bigger) that keeps climate survivable in the middle of a supercontinent

Any suggestions how to improve this idea? Any idea how deep I could make it before I make geologists outraged?
 
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  • #2
You mean something like Canyon (Niven: n-space)?
 
  • #3
First thing I thought of too.

The entire population of the planet lives in a crevasse - the lowest part of the planet, where all the atmosphere of the planet has gathered.

Best not ask how that crevasse got there. Especially not in a Kzinti Bar.
 
  • #4
Simon Bridge said:
You mean something like Canyon (Niven: n-space)?

[googling]

Damn, someone already thought about it.

DaveC426913 said:
Best not ask how that crevasse got there.
My idea was continental rift - continent is slowly splitting, as Pangea did it, or we see now in East African Rift. Plausible mechanism or not specially?

Anyway, it makes the story even a more thrilling because of impending doom - in maybe 10 mln years the split would be big enough to be connected with ocean :D
 
  • #5
Czcibor said:
[googling]

Damn, someone already thought about it.

My idea was continental rift - continent is slowly splitting, as Pangea did it, or we see now in East African Rift. Plausible mechanism or not specially?

Anyway, it makes the story even a more thrilling because of impending doom - in maybe 10 mln years the split would be big enough to be connected with ocean :D
Well, the trouble with it happening over a long timeline is that erosion will tend to level things out.

Things that have created crevasses in a shorter timeline:

- planetary collision - Mars sustained a gigantic hit sometime in its past that created a huge depression on one side, the biggest volcano in the solar system on the other side, and the biggest canyon in the solar system between them.

- Mars aquifers (underground bodies of water) have erupted and carved great riverbeds in its ancient historyThis last one is pretty plausible on an exoplanet. Doesn't really require a planetary collision, and doesn't require millions of years for cooling. Aquifer erupts, huge volumes of water carve a deep canyon, then evaporates.
 
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  • #6
How to get really deep depresion on an exoplanet?

Think about how far you are away from home.
 
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  • #7
DaveC426913 said:
Well, the trouble with it happening over a long timeline is that erosion will tend to level things out.

It would indeed tend to, but it not prevent the lake to be quite deep:
The bottom of the lake is 1,186.5 m (3,893 ft) below sea level, but below this lies some 7 km (4.3 mi) of sediment, placing the rift floor some 8–11 km (5.0–6.8 mi) below the surface: the deepest continental rift on Earth.
http://en.wikipedia.org/wiki/Lake_Baikal

Anyway, how to keep sedimentation to minimum? High mountains that block most of winds in the valley? Water not coming from a river, but seeping through aquifers?

- planetary collision - Mars sustained a gigantic hit sometime in its past that created a huge depression on one side, the biggest volcano in the solar system on the other side, and the biggest canyon in the solar system between them.
Shouldn't a geologically active planet like Earth react with lots of lava coming out of the crater?

- Mars aquifers (underground bodies of water) have erupted and carved great riverbeds in its ancient historyThis last one is pretty plausible on an exoplanet. Doesn't really require a planetary collision, and doesn't require millions of years for cooling. Aquifer erupts, huge volumes of water carve a deep canyon, then evaporates.
Interesting, that's something that have not thought about. How deep can they be?
 
  • #8
One more thing that started to bug me - would such depression be much, much hotter than the surroundings? I mean on Earth it is 6C/1000m. Would rule like that be also applicable in case of a deep depression? (because you know 7000 m would give something like 42 C more than on the sea level) Or its enough to make it somewhat hotter, but with no excess?
 
  • #9
I started to toy with asteroid idea.

On Mars something like that worked - Hellas Planitia, 7.1 km deep, 2300 km wide. Sounds quite satisfying.
http://en.wikipedia.org/wiki/Hellas_Planitia

The only minor drawback:
Cretaceous–Paleogene extinction event left Chicxulub crater, which is 180 km wide.

In optimistic scenario - back to bacteria?
 
  • #10
Lower gravity allows higher mountains but also smaller pressure gradients for the atmosphere, that does not help I think. Colder temperatures would help, but that leads to other problems. You can reduce the oxygen content of the atmosphere.

Subduction zones can give depressions - the Mariana trench is one example, several kilometers below the surrounding ocean floor.
 

1. How do we know if an exoplanet has an atmosphere?

There are a few ways to determine if an exoplanet has an atmosphere. One method is to observe the planet as it transits in front of its host star. Changes in the star's light as the planet passes in front of it can indicate the presence of an atmosphere. Another method is to study the planet's spectral signature, which can reveal the chemical composition of its atmosphere.

2. What factors contribute to the depth of depression on an exoplanet?

The depth of depression on an exoplanet can be influenced by a variety of factors, including the planet's size, mass, and distance from its host star. A larger planet with a stronger gravitational pull will likely have a deeper depression, while a smaller planet may have a shallower depression. The distance from the host star also plays a role, as the amount of solar radiation and atmospheric escape can impact the depth of depression.

3. Can we measure the depth of depression on an exoplanet?

Yes, we can measure the depth of depression on an exoplanet using a variety of techniques. One method is to study the planet's transit, looking for changes in the star's light as the planet passes in front of it. Another method is to analyze the planet's spectral signature, which can reveal the depth of the atmosphere and the presence of any depressions.

4. How does the depth of depression on an exoplanet affect its habitability?

The depth of depression on an exoplanet can have a significant impact on its habitability. A deeper depression can trap heat and create a greenhouse effect, making the planet too hot for life to survive. On the other hand, a shallower depression may not be able to retain enough atmosphere to support life. The depth of depression must be within a certain range for an exoplanet to be considered potentially habitable.

5. Can we simulate the conditions of an exoplanet to study depression?

Yes, scientists can use computer models and simulations to study the conditions of an exoplanet and its depression. By inputting data about the planet's size, mass, distance from its star, and other factors, researchers can create models that simulate the atmospheric conditions and depth of depression on an exoplanet. These simulations can help us better understand the potential habitability of these distant worlds.

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