[HN Gopher] The Tarnished Moon
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The Tarnished Moon
Author : uncertainquark
Score : 94 points
Date : 2021-04-08 17:26 UTC (5 hours ago)
(HTM) web link (www.psrd.hawaii.edu)
(TXT) w3m dump (www.psrd.hawaii.edu)
| unchocked wrote:
| Fascinating. I wonder how long it took to oxidize, and what the
| partial pressure of oxygen blown that far out is.
|
| Shuai Li also recently mapped direct evidence for water on the
| Moon, using similar data. Exciting times for lunar geology.
|
| https://www.pnas.org/content/115/36/8907
| tape_measure wrote:
| See also https://en.m.wikipedia.org/wiki/Corrosion_in_space
|
| Atomic oxygen resistance is a consideration for any object in
| Earth orbit, and now it seems to be relevant for the moon as
| well. It would be interesting to know the oxygen flux and to
| study the Apollo hardware left on the moon for corrosion and
| erosion.
|
| Interestingly enough, ozone (O3) is a concern for rubber objects
| on the earth's surface. Modern engineering rubbers are stabilized
| against ozone attack.
|
| What horrible sulfur/oxygen species will we find around Venus?
| question000 wrote:
| I read somewhere that the typical density of matter in the
| "vacuum" of space is about one helium atom per square meter.
|
| Is that true? Seems kinda crowded out there.
| enriquto wrote:
| > one helium atom per square meter
|
| this is an infinite density!
| CapitalistCartr wrote:
| Cubic centimeter, and it depends on where. For instance, in the
| Solar System, between stars, or between galaxies? In the Solar
| System, the solar wind has an average density of 3 to 10
| particles (mostly protons and electrons) per cc, but it's lower
| the farther out from the Sun.
| mankyd wrote:
| I'd be curious about the source. Is that one He in the actual
| vacuum, or is that one He by dividing known matter by known
| space. If its the latter, that's very different.
| amadsen wrote:
| Perhaps not as different as you think! Most of the "known
| matter" is indeed H and He drifting in otherwise "empty
| space". Stars, while very dense, are few and far between on
| cosmic scales. In terms of mass, the ratio is about 4:1. So
| you'd get quite similar answers from both calculations.
| wongarsu wrote:
| It depends on where we are talking about. Inside the solar
| system is the heliosphere [1] with lots of particles from
| solar wind. As you leave the solar system you get the
| interstellar medium [2], which is about 90% hydrogen and 10%
| helium, most of it about half a particle per cm^3. Between
| the galaxies there's the intergalactic medium [3], which is
| speculated to contain about half of (normal, not-dark) matter
| in tendrils with a density of about 1-10 particles per cm^3
| (and a lot less outside those tendrils).
|
| The best vacuums we can produce artificially on earth have a
| couple billion particles per cm^3.
|
| 1: https://en.wikipedia.org/wiki/Heliosphere
|
| 2: https://en.wikipedia.org/wiki/Interstellar_medium
|
| 3: https://en.wikipedia.org/wiki/Warm%E2%80%93hot_intergalact
| ic...
| nicklecompte wrote:
| I think that is the estimate for the warm intergalactic medium;
| within galaxies, densities are more like 100-1,000 H atoms /
| meter at their most sparse.
|
| So intergalactic space is "crowded" compared to, say, the
| vacuums at CERN, but quite "spacious" compared to the outer
| space between stars in a galaxy (and certainly compared to the
| space between the Earth and the moon).
|
| I guess I'm not sure what an "appropriate" density would be :)
| 1 measly ice-cold hydrogen atom within a cubic meter is slim
| pickings.
| [deleted]
| mrfusion wrote:
| Could the moon not be as we were told?
| nightfly wrote:
| ...what are you suggesting the moon "is" then?
| Zancarius wrote:
| Well, it's certainly not made out of cheese, much to my
| chagrin!
|
| The thing that I've found so interesting about oxidation of the
| lunar surface ever since it was announced is the extent to
| which Earth, err, contaminates its nearest neighbor. Molecular
| oxygen is one of the bio-signatures in astrobiology one might
| look for in a search for life, so I would imagine that if the
| "clouds" (for lack of a better term) extend quite a ways
| outward from the origin planet, it _might_ lend itself to
| easier detection with less sensitive instrumentation than
| previously thought.
|
| I'm sure there are plenty of other interesting implications too
| that really smart astrophysicists are working toward in the
| search for extraterrestrial life forms.
|
| But, I'm not an astrophysicist, and I may very well be dreaming
| up idiotic notions that are impossible.
| kwhitefoot wrote:
| > not made out of cheese,
|
| You mean those intrepid explorers Wallace and Gromit lied?
| Jun8 wrote:
| "So where does the oxygen come from? Shuai Li and team suggest it
| comes from Earth's upper atmosphere. ... The effect would be
| strongest on the Moon's Earth-facing hemisphere, consistent with
| the distribution determined by Li and colleagues using M3 data."
|
| High-res photos of moon regularly show the red areas, e.g.
| https://www.reddit.com/r/space/comments/exf4yp/one_year_ago_...
| secondcoming wrote:
| Yet another article about Rust.
| igorstellar wrote:
| Come on, what's up with downvotes? That was really smart joke.
| Already__Taken wrote:
| I voted, that was a fun joke. 100% a reddit comment though.
| birdyrooster wrote:
| Coming onto Hacker News and having fun? He scored an own
| golang.
| sidlls wrote:
| HN is too full of itself. n-gate.com is funny because it's
| accurate.
| unchocked wrote:
| True. It's hilarious, and mercifully not spamming the
| comment thread.
| de_keyboard wrote:
| I have to downvote to hide this.
| kemonocode wrote:
| My HN experience has considerably improved ever since
| finding out about n-gate.com, especially when it comes to
| summarizing long threads in a satirical way or if there's a
| big story I might have missed.
| SllX wrote:
| A Hackernews violates the Prime Directive.
| jcpham2 wrote:
| Nice
| serverholic wrote:
| Take your upvote and get out
| sedatk wrote:
| Reddit's leaking.
| craftinator wrote:
| But is the Moon memory safe?
| elihu wrote:
| Well, if you do any unsafe operations, all bets are off.
| There aren't many useful things you can do on the moon that
| aren't unsafe operations. SpaceX is working on self-driving
| rockets that wrap some of the unsafe operations and provide a
| safe interface, but opinions vary on how safe the resulting
| system will actually be.
| rriepe wrote:
| The Earth's atmosphere is shaped like a flame, not a big
| sphere[1]. It's so huge that the Moon moves _through_ it,
| dragging along a little faux-atmosphere with it.
|
| It's surprising that heavier O2 molecules can get out there, but
| it's not a place with no atmosphere.
|
| [1]: https://www.space.com/earth-atmosphere-extends-beyond-
| moon.h...
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(page generated 2021-04-08 23:00 UTC)