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A newly discovered moon tunnel

washingtonpost.com

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Re: A newly discovered moon tunnel

#121

Post by Brybry »

samstave wrote: post #19
yosyp wrote: post #8

For a more technical description, the paper is here: http://onlinelibrary.wiley.com/doi/10.1002/2017GL074998/full . "Detection of intact lava tubes at Marius Hills on the Moon by SELENE (Kaguya) Lunar Radar Sounder" Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon's composition and potentially serve as secure shelters for humans and instruments. We investigated the SE…

If the moon had ancient volcanic activity and thus, why is it, after observable impact from various bodies - shown in the craters all over the surface, and the sumizing of the fact that water was deposited to earth from extra-orbital impacts... does the moon have zero water or atmosphere? Where did water originate? (I didn't know how to format that question any better, so please forgive the fumbly format)

I saw a recent study that said the moon probably did have atmosphere from volcanic activity... but only for around 70 million years. It dissipated into space.

http://www.sciencedirect.com/science/article/pii/S0012821X17...

Re: A newly discovered moon tunnel

#122

Post by valuearb »

AgentME wrote: post #108
shusson wrote: post #101

Earlier quoted context omitted.

I would love to know the rough cost to send a probe to the moon.

If only there were terrorists on the moon, then no one would worry about the cost.

You just made me start rooting for Iran’s space program.

Re: A newly discovered moon tunnel

#124

Post by valuearb »

ballenf wrote: post #22
kseverest wrote: post #12

I wonder how stable such tubes would be? No water erosion, no earthquakes, even though they must have formed at a time that was more geologically active. They could be on the edge of collapse if say, a large vehicle drove in them. Am I wrong? Just a first thought. Other than that, they could probably serve as a goal for human spaceflight, an intermediate step between walking on the moon and colonizing mars.

The article mentions the use of inflatable housing inside. Seems like a wise move given we have so little experience with their stability. If they've survived this long, then presumably they are very unlikely to collapse on their own. That is, settlers would only need to worry about collapse cause by their own movements. The odds of them being 'on the verge of collapse' are relatively low in my thinking. Unless there…

Wouldn’t the acceleration of falling objects be slow enough that the force delivered be much lessened?

Re: A newly discovered moon tunnel

#125

Post by kurthr »

comicjk wrote: post #91
kurthr wrote: post #64

Earlier quoted context omitted.

At reasonable temperatures, yes, the clouds turn into water and release energy, hydrogen burns. Water is entropically preferred as a lower energy state than separate atoms/molecules because of lower enthalpy at reasonable temperatures. Depending on density and ignition sources the reaction rate may vary, but it doesn't have to explode in a ms when there is a billion years available.

That's not what "entropically preferred" means. If something is a lower-energy state, it's energetically preferred, but may or may not be entropically preferred. Water is NOT - entropy would prefer simpler molecules over more structured molecules. I think the concept you're thinking of is free energy, which determines the final destination of a process. The equation relating these things is (change in free energy) =…

No, since this was chemistry, I was talking about enthalpy of an exothermic reaction (negative enthalpy), and interstellar space is pretty close to constant pressure, but not constant entropy for Gibbs free energy.

In any case: dH=TdS + Vdp note dp is small in space but V can be large and dS is the change in entropy.

...and enthalpy of ideal (interstellar H & O) gases does not depend on pressure, unlike entropy and Gibbs energy. If you really just mean free energy U, then they are basically the same thing in open space (but not in a plasma), a distinction without difference.

For further pedantics I recommend Wikipedia, since I doubt we are helping anyone else.

Re: A newly discovered moon tunnel

#127

Post by kobeya »

waegawegawe wrote: post #77
LeifCarrotson wrote: post #72

Earlier quoted context omitted.

A Martian atmosphere (not sure about a lunar atmosphere) would be lost on a timescale of tens of millions of years. That's very quick in cosmological timescales, but slow enough that any human effort to create or replenish it could be very successful.

That said, the earth's atmosphere has a mass of about five billion billion tons. For reference, as a species, we produce about ten billion tons of concrete each year. This is just to give a sense to the scale of effort involved in replacing a planetary atmosphere.

Also many thermoforming efforts consider adding an artificial dynamo (using, say, superconducting rings) to protect both the atmosphere and life on the surface. The energy cost of maintaining an artificial dynamo would be less than the incremental maintenance cost of maintaining atmosphere and dealing with health risks from radiation.

Re: A newly discovered moon tunnel

#128

Post by kobeya »

waegawegawe wrote: post #115
larkeith wrote: post #86

Earlier quoted context omitted.

Depending on the volume of surface ice (especially at the poles), might it be possible to produce atmosphere on a massive scale via orbital lenses or mirrors? With recent advances in solar sail technology, I can't imagine the implementation would be too far removed from current capabilities.

Think about how large of a lens you're talking about. Even if it were one hundred meters across and was able to collect 100% of the sun's energy passing through it, the amount of energy produced would be utterly insignificant compared to the problem we're discussing. And how would you get a one hundred meter lens to mars orbit? Even after that, you have to consider that we want an oxygen atmosphere, not one made of w…

That's about ~250x the JWST. Given that we're talking about a society that has developed far enough to be sending people to Mars and terraforming the landscape, I don't think that 8 doublings would be an unreasonable multiplier of current capability. Still a flagship, many-decade mission though.

Re: A newly discovered moon tunnel

#130

Post by extrapickles »

icanhackit wrote: post #76
kirillkh wrote: post #68

Earlier quoted context omitted.

Then we have no hope of ever engineering Mars to have enough air for us to breath?

NASA proposes building artificial magnetic field to restore Mars’ atmosphere: https://www.universetoday.com/134052/nasa-proposes-magnetic-...

Interesting, it only needs a 1-2 Tesla magnetic field. MRI machines go up to 3T, which means this isn't too outlandish with known technology. The main issue is that they probably want a Mars sized field at 1-2T.
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