Problems With a Terraformed Moon -- Maybe?

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Discussion Overview

The discussion revolves around the feasibility and implications of terraforming the Moon, particularly focusing on the potential for creating an atmosphere, introducing water, and the effects on the Moon's gravitational pull. Participants explore theoretical, technical, and practical aspects of this concept, including the sources of water and the necessary conditions for liquid water to exist.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question how a large amount of water could be transported to the Moon, suggesting that any water would likely need to come from existing lunar sources, thus not changing the Moon's mass.
  • Others propose that asteroids or comets could be used as sources of water, with some discussing the feasibility of mining water from asteroids in stable orbits.
  • There are claims that adding water and an atmosphere would increase the Moon's mass, potentially affecting its gravitational pull, but others argue that the increased radius would have a more significant impact on surface gravity than the added mass.
  • Participants discuss the percentage of Earth's mass attributed to water and atmosphere, noting that while they cover a large surface area, they constitute a small fraction of total mass.
  • Some argue that creating oceans on the Moon is economically inefficient compared to building artificial habitats, which could be more practical for sustaining life.
  • There is a discussion about the conditions necessary for liquid water to exist, emphasizing that pressure, rather than gravity, is crucial for maintaining liquid states.
  • Concerns are raised about the Moon's ability to retain an atmosphere over geological timescales due to its lower gravity and the potential for atmospheric escape.
  • Some participants suggest that while it is theoretically possible to create a Titan-like atmosphere on the Moon, the practical challenges of sourcing the necessary materials are significant.

Areas of Agreement / Disagreement

Participants express a range of views on the feasibility of terraforming the Moon, with no consensus reached on the practicality of creating oceans or sustaining an atmosphere. Disagreements exist regarding the implications of added mass on gravitational pull and the sources of water needed for such endeavors.

Contextual Notes

Limitations include unresolved questions about the sources of water, the assumptions regarding the Moon's ability to retain an atmosphere, and the economic viability of different approaches to creating habitable environments.

  • #31
nikkkom said:
You missed the point. The water molecules are not just in the habitat. They _stay in the cup_. Outside, they will not.
I probably need to stop responding.
OK this is my last reply for your response: You can read what mfb wrote here. And without a proper surface gravity, your water molecules will be gone no matter where you place your cup. And also read the second paragraph of my previous post.
 
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  • #32
nikkkom said:
On the airless Moon, water would boil and thus escape right away (a meter-thick global layer would be gone in a few years).
Where does that time estimate come from? The water vapor still has to get split to have individual hydrogen atoms. That should happen slower than the evaporation/boiling. No matter how much atmosphere there is, the amount of water that evaporates/boils is the same.
 
  • #33
mfb said:
Where does that time estimate come from? The water vapor still has to get split to have individual hydrogen atoms.

Yes, as you correctly noticed, the main thing is that a 1-meter water layer would completely evaporate because under its full weight at Moon, ~0.015 bar of pressure, boiling temp is below 20 C. So the conditions would be much closer to today's Mars than to anything "terraformed".

And this assumes that all water stays as vapor. Not the case. Taking into account slow rotation of the Moon, it is much hotter than 20 C during days (IIRC it's more like 90 C), and much below freezing during night, so even less water vapor will actually *be* an atmosphere.

Mean thermal velocity of water at 20 C is 585 m/s and is substantially lower than escape velocity 2380 m/s, but not as drastically lower as on Earth. High-speed tail of Maxwell–Boltzmann will be substantial. I have no tools here to calculate with good precision how fast it would be, I could be well wrong about "a few years", it might well be up to 100 years, but it's much, much faster than even on Mercury:

water_escape.png
 

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