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A newly discovered moon tunnel

washingtonpost.com

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Re: A newly discovered moon tunnel

#71

Post by JumpCrisscross »

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?

> Why couldn't the Earth have formed with its own water?

We’re not sure from where Earth’s water came [1]. Some evidence suggests the Earth was born with all its water, some that most came from comets.

[1] https://en.m.wikipedia.org/wiki/Origin_of_water_on_Earth

Re: A newly discovered moon tunnel

#72

Post by LeifCarrotson »

kirillkh wrote: post #68
spdustin wrote: post #60

Earlier quoted context omitted.

The moon's core isn't made of the swirling molten iron dynamo like Earth's is. No swirling molten iron, no magnetic field. No magnetic field, nothing deflects the solar wind that then, literally, blows away any fledgling atmosphere. It's believed that Mars' atmosphere was considerably more dense than it is today, but along the way, its core cooled, and it lost its protective magnetic shield, allowing the solar wind t…

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

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.

Re: A newly discovered moon tunnel

#73

Post by DougWebb »

ealloc wrote: post #65
kurthr wrote: post #29

Earlier quoted context omitted.

The same place that water came from on Earth... comet impacts and residual moisture from the impact that split the Earth-Moon system. Really the same place all planetary water and gas has come from. There's not much left because it mostly boils off due to low pressure, but in dark crevasses it's likely to stay cold enough to remain condensed. It's been measured spectroscopically.

The reason water exists on earth, and not on mars, may be that life on earth saved the water by discovering photosynthesis. The discovery of photosynthesis caused the "great oxygenation event" which pumped oxygen into the atmosphere. Oxygen reacts with atmospheric hydrogen to form water. Without the oxygen, the very light hydrogen molecules would float to the top of the atmosphere and are easily blown away by solar w…

That seems like it must be incorrect. Life on earth evolved in the oceans, so the oceans had to exist for eons before life evolved and the eons it took for life to evolve photosynthesis and produce significant amounts of oxygen in the atmosphere. If what you're saying is correct, then the earth either started out with much more water than it has now, or the hydrogen escaped a lot more slowly than I'd expect it to.

Re: A newly discovered moon tunnel

#75

Post by DougWebb »

nkoren wrote: post #58
galaxyLogic wrote: post #20

Earlier quoted context omitted.

> 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?

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.

Re: A newly discovered moon tunnel

#76

Post by icanhackit »

kirillkh wrote: post #68
spdustin wrote: post #60

Earlier quoted context omitted.

The moon's core isn't made of the swirling molten iron dynamo like Earth's is. No swirling molten iron, no magnetic field. No magnetic field, nothing deflects the solar wind that then, literally, blows away any fledgling atmosphere. It's believed that Mars' atmosphere was considerably more dense than it is today, but along the way, its core cooled, and it lost its protective magnetic shield, allowing the solar wind t…

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-...

Re: A newly discovered moon tunnel

#77

Post by waegawegawe »

LeifCarrotson wrote: post #72
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?

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.

Re: A newly discovered moon tunnel

#78

Post by DougWebb »

ballenf wrote: post #27
kharms wrote: post #2

When such discoveries are made who "owns" that real estate?

Are there any figures on the minimum $/gram of minerals that would justify a mining mission (presumably unmanned)? Just can't imagine that gold, platinum or any stable metal would be worth it. Maybe high grade diamonds that don't need to be extracted from other rock. The surveys would have likely identified the presence of such a high density substance and we haven't seen any mention of it. I know you probably meant…

The most common elements on the moon are quite common on the earth too; I don't think the value in mining them will ever come from bringing the mined materials back to earth. The value is going to come from having and maintaining an established base on the moon. The moon is a high point in the earth's gravity well that's full of raw materials that can be used to build things that can go further out. Mining on the moon is going to be about building and supplying interplanetary (and maybe interstellar) spaceships, not selling jewelry back on earth.

[0] https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_...

Re: A newly discovered moon tunnel

#79

Post by larkeith »

kirillkh wrote: post #68
spdustin wrote: post #60

Earlier quoted context omitted.

The moon's core isn't made of the swirling molten iron dynamo like Earth's is. No swirling molten iron, no magnetic field. No magnetic field, nothing deflects the solar wind that then, literally, blows away any fledgling atmosphere. It's believed that Mars' atmosphere was considerably more dense than it is today, but along the way, its core cooled, and it lost its protective magnetic shield, allowing the solar wind t…

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

I don't know the rate of atmospheric loss, but it might be possible to introduce air at a high enough rate to outstrip the losses, making for a sustainable atmosphere. It would presumably depend on the availability of ice and other volatiles.

Re: A newly discovered moon tunnel

#80

Post by comicjk »

samstave wrote: post #54
gjjrfcbugxbhf wrote: post #45

Earlier quoted context omitted.

Water is just hydrogen plus oxygen. Both are fairly common elements in the universe.

Under what circumstances does one need to have in order to make them combine into water, organically? (Meaning without any device or machine, assume you have two big clouds of each element floating in space - if they collide, do the naturally just form into water molecules?)

Yes, oxygen and hydrogen mixed together will eventually react to form water. To react, atoms or molecules simply need to collide hard enough to overcome their initial repulsion and form bonds. In space it is a slow process, because the pressure and temperature are both low - this means the atoms rarely hit each other, and when they hit, they don't hit very hard.
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