The Tarnished Moon | Hacker News Reader

The Tarnished Moon

psrd.hawaii.edu

108 pointsuncertainquark33 comments

"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_...

The large reddish regions in this stitch do not seem to correlate with the concentrations of hematite that researchers detected.

> The maps show the hematite occurrences at latitudes greater than 75 degrees but in fact, almost all the hematite detections occur at latitudes greater than 60 degrees. Furthermore, an asymmetry exists in the distribution of hematite: In both polar regions, most of the hematite detections are on the Earth-facing hemisphere (the Earth direction is 0 degrees on each map). Finally, the floors of craters (visible as shaded relief beneath the colors on the maps) rarely contain hematite signals; flat places do not have much hematite. So, hematite is associated with the Earth-facing directions of the lunar polar regions.

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...

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?

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.

> one helium atom per square meter

this is an infinite density!

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.

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.

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_intergalactic...

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.

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.

>So intergalactic space is “crowded” compared to, say, the vacuums at CERN

I vaguely recall Sam's Laser FAQ claimed that terrestrial vacuum pumps couldn't do as well as outer space, due to outgassing of materials and diffusion through vacuum chamber walls.

The CERN page on the LHC vacuum system says it gets down to 10^-13 atmospheres. https://home.cern/science/engineering/vacuum-empty-interstel... The wikipedia article on vacuum gives a range for "deep space" from 10^-10 to 10^-20. Interstellar, but maybe not intergalactic.

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

Yet another article about Rust.

Take your upvote and get out

Reddit's leaking.

Come on, what’s up with downvotes? That was really smart joke.

Coming onto Hacker News and having fun? He scored an own golang.

HN is too full of itself. n-gate.com is funny because it's accurate.

True. It’s hilarious, and mercifully not spamming the comment thread.

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.

A Hackernews violates the Prime Directive.

I have to downvote to hide this.

I voted, that was a fun joke. 100% a reddit comment though.

But is the Moon memory safe?

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.

Mmm, sounds like the moon is just inherently dangerous, and trying to say that we should do things safely on the moon is like telling us just not to go there at all.

Nice

Could the moon not be as we were told?

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.

> not made out of cheese,

You mean those intrepid explorers Wallace and Gromit lied?

I think so!

...what are you suggesting the moon "is" then?

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