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A newly discovered moon tunnel

washingtonpost.com

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Re: A newly discovered moon tunnel

#81

Post by njarboe »

pjungwir wrote: post #67
JumpCrisscross wrote: post #61

Earlier quoted context omitted.

> Where did the comets get the water they impacted on earth? Hydrogen comes from primordial nucleosynthesis [1] and makes up most of the interstellar medium [2]. Oxygen is produced when neutron stars collide and stars explode [3] as well as when some stars burn [4]. These freely combined in the gas disk from which our solar system formed, condensing into planets, moons, comets and other things [5]. [1] https://en.m.w…

Thank you for this answer! But then why does the water have to come from comets? Why couldn't the Earth have formed with its own water? Also, we seem to have a lot of water. It's really all from comets, a little here, a little there?

Earth likely had some water during early creation (accretion) but the best theory on how the Moon formed is that a Mars sized object hit the early Earth at the end of accretion. This blasted much of the Earth's rock part (mantle) and any water it might have had into orbit. The rock part quickly fell back to Earth and the rest condensed and collapsed to form the moon. The water and other volatilizes that were on Earth were blown away by the solar wind at that time. The surface of the Earth and Moon would have been boiling lava at this point and had to accumulate water from new impacts of comets and icy asteroids.

The water on Earth may seem to be a lot to us on the surface but it is only about 0.02% by mass [1].

https://www.universetoday.com/65588/what-percent-of-earth-is...

Re: A newly discovered moon tunnel

#82

Post by robryk »

DougWebb wrote: post #75
nkoren wrote: post #58

Earlier quoted context omitted.

This is the correct answer. These lava tubes are, at their youngest, a couple billion years old. Since then, the moon has been thwacked very hard and -- on those timescales -- often. If the tubes haven't collapsed yet, then there's a high likelihood that they're exceptionally stable.

That could be survivor bias. Maybe there used to be a lot more of them.

Wouldn't a collapsed tube be very distinctive visually?

Re: A newly discovered moon tunnel

#84

Post by nkoren »

robryk wrote: post #82
DougWebb wrote: post #75

Earlier quoted context omitted.

That could be survivor bias. Maybe there used to be a lot more of them.

Wouldn't a collapsed tube be very distinctive visually?

Very much so -- and one has even been explored by humans!

https://en.wikipedia.org/wiki/Hadley%E2%80%93Apennine

Re: A newly discovered moon tunnel

#85

Post by njarboe »

DougWebb wrote: post #75
nkoren wrote: post #58

Earlier quoted context omitted.

This is the correct answer. These lava tubes are, at their youngest, a couple billion years old. Since then, the moon has been thwacked very hard and -- on those timescales -- often. If the tubes haven't collapsed yet, then there's a high likelihood that they're exceptionally stable.

That could be survivor bias. Maybe there used to be a lot more of them.

Yes survivor bias. But since these survived, they are likely to be structurally sound. Like antique furniture or structures on Earth.

Re: A newly discovered moon tunnel

#86

Post by larkeith »

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.

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.

Re: A newly discovered moon tunnel

#87

Post by larkeith »

DougWebb wrote: post #75
nkoren wrote: post #58

Earlier quoted context omitted.

This is the correct answer. These lava tubes are, at their youngest, a couple billion years old. Since then, the moon has been thwacked very hard and -- on those timescales -- often. If the tubes haven't collapsed yet, then there's a high likelihood that they're exceptionally stable.

That could be survivor bias. Maybe there used to be a lot more of them.

Does that count as natural selection?

Re: A newly discovered moon tunnel

#89

Post by QAPereo »

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…

The moon is pretty dead, so no processes exist... if they’re stable, barring asteroid strike. They’d remain stable. The problem is metastability, the “death block” problem in ice climbing.

Re: A newly discovered moon tunnel

#90

Post by knappe »

galaxyLogic wrote: post #20
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.

> no earthquakes No but how about moon-quakes? Ok, not geologically active you say. But moon's been bombarded by asteroids it's surface is full of craters. Creating a crater wouldn't that be an equivalent of a moon-quake?

You're not accounting for tidal forces. The same forces that create the tides on Earth also affect the moon. In this case via moon-quakes.

https://phys.org/news/2017-08-moon-tidal-stress-responsible-...

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