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Aristarchus crater, radioactive?

mhaze

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mhaze
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Jan 10, 2007
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Aristarches crater, visible with the eye, upper right quadrant of full moon.

Radon-222 has been detected a couple times there.

It has a half life of just a couple days and is a known byproduct of U238 decay.

Now, how does this make sense? There are known to have been "natural nuclear reactors" on the Earth, but they all cooled down billions of years ago.
 
mhaze said:
Aristarches crater, visible with the eye, upper right quadrant of full moon.

Radon-222 has been detected a couple times there.

It has a half life of just a couple days and is a known byproduct of U238 decay.

Now, how does this make sense? There are known to have been "natural nuclear reactors" on the Earth, but they all cooled down billions of years ago.
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Umm no http://en.wikipedia.org/wiki/Radon#Natural

But the crater is famous for TLPs over the years
 
In what way does this not make sense to you? And why bring in natural nuclear reactors??

You seem to have answered your own question. Radon is in the decay chain for uranium.
 
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Radon gas can rise to dangerous levels in cellars in Aberdeen, Scotland. The older buildings are made of granite, and radioactive decay of trace elements produces significant amounts of radon. This is not to suggest that old buildings in Aberdeen are the sites of natural nuclear reactors. I don't see why that would be required to account for the radon.
 
MG1962 said:
...But the crater is famous for TLPs over the years
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[CT-MODE]

Transient phenomena, and it's radioactive?

Wake up people. Obviously this is the location of the alien base the government of the world has been hiding from us all these years!

[/CT-MODE]
 
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RecoveringYuppy said:
In what way does this not make sense to you? And why bring in natural nuclear reactors??

You seem to have answered your own question. Radon is in the decay chain for uranium.
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For uranium 238. So the probable explanation then is that there are some large deposits of uranium, most likely reduced ore containing O2 down underneath the crater, and the fraction of that mineral which is u238 is producing the gas, then it continually migrates to the surface as it does on Earth.

I see the Wiki article on Radon indicates that IT'S MOST STABLE isotope has a half life of only a few days. So the mechanism on the Moon is the same, excepting possibly the curiosity that the emissions are only found in the vicinity of that particular crater.

Also interesting, this article

http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

indicates that water serves as the neutron moderator for a natural reacter, so that would likely never have occurred on the Moon.

But they think they've found one currently active on Mars.
 
I'm still not seeing the connection here. What does the presence of U-238 have to do with a natural fission reactor?
 
MG1962 said:
Umm no http://en.wikipedia.org/wiki/Radon#Natural

But the crater is famous for TLPs over the years
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No evidence that the several readings of radioactive radon-222 is related to the TLP, on the contrary, the rn222 might be guessed to be constant, as opposed to temporary.

From this link

http://www.webelements.com/radon/

note that radon is typically prepared from radium, and that 2/3 a cc per month per gram of radium is typical production. Radium, as well as uranium, could cause this the rn222 readings from the instruments.

As one of the noble gases, radon flouresces yellow, or yellow red.

The "yellow red" could account for the red TLP, but most IIRC were blue.
 
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Actually, 222Rn is produced more from a natural U deposit than from a nuclear reactor. Reactors don't generically make "radioactivity", they drive very specific nuclear reactions which do not make extra radon. (Not 222Rn, anyway, and the detection is specific to this isotope. Or, at least, in a few minute's looking, I can't construct a slow-neutron reaction that does this. Some fast-neutron X(n,nn) options exist.) The only way to get Rn222 is to take a pile of 238U, then sit around and wait. (One of the things you're waiting for is for the 238U to decay to short-lived 226Ra---this is why Curie found that radium emits radon. It's not a separate natural process.)

In order to get enough radon gas that it emits detectable atomic fluorescent light, I should think it'd also be so radioactive that the moon's surface would literally melt. Whatever it is, I'm skeptical that you have a source for radon "fluorescing" "yellow" "as one of the noble gases". Other noble gases emit various colors, and I'm not aware of any radon experiment with enough material to detect generic fluorescence.
 
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ben m said:
Actually, 222Rn is produced more from a natural U deposit than from a nuclear reactor. Reactors don't generically make "radioactivity", they drive very specific nuclear reactions which do not make extra radon. (Not 222Rn, anyway, and the detection is specific to this isotope. Or, at least, in a few minute's looking, I can't construct a slow-neutron reaction that does this. Some fast-neutron X(n,nn) options exist.) The only way to get Rn222 is to take a pile of 238U, then sit around and wait. (One of the things you're waiting for is for the 238U to decay to short-lived 226Ra---this is why Curie found that radium emits radon. It's not a separate natural process.)
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Makes sense.

ben m said:
In order to get enough radon gas that it emits detectable atomic fluorescent light, I should think it'd also be so radioactive that the moon's surface would literally melt. Whatever it is, I'm skeptical that you have a source for radon "fluorescing" "yellow" "as one of the noble gases". Other noble gases emit various colors, and I'm not aware of any radon experiment with enough material to detect generic fluorescence.
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No. Because that's not what the references say.

http://chemistry.about.com/od/elementfacts/a/radon.htm

as an example.

I guess if the gas condenses to solid at -71C, given the wide range of lunar temperatures, "solid radon" deposits could account for at least the red. Speculative, but I am just trying to derive some possible causation for the TLP.

That is, of course, aside from the giant alien fusion reactors buried in the crater.

:)
 
mhaze said:
No. Because that's not what the references say.
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Interesting! Yeah, I was thinking of gaseous radon. Solid radon is a terrifying thing to contemplate, and I'm pretty sure it is not present on the moon, even in the wildest alternative theory.
 
ben m said:
Interesting! Yeah, I was thinking of gaseous radon. Solid radon is a terrifying thing to contemplate, and I'm pretty sure it is not present on the moon, even in the wildest alternative theory.
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Yeah I know this is crazy weird stuff here, but hey, the crater glows. And just sometimes....

By the way, here's a run of the area from the recent LRO / LOLA area to 1/2 meter resolution. Keep in mind this is a radar 3d map database displayed in gray scale visual.

ride a helicopter around the place, sort of...

http://wms.lroc.asu.edu/lroc_browse/view/M175569775

I kind of think there won't be any astronauts walking on those sands.

Now to figgur the blue color TLP.
 
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ben m said:
Interesting! Yeah, I was thinking of gaseous radon. Solid radon is a terrifying thing to contemplate, and I'm pretty sure it is not present on the moon, even in the wildest alternative theory.
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Why not? Moon's nightside is rather colder than -71 C, so any radon present (if at all) would have to be solid.
 
Mark6 said:
Why not? Moon's nightside is rather colder than -71 C, so any radon present (if at all) would have to be solid.
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a) It doesn't count as "solid", in some sense, unless you're talking about more than a monolayer. "One radon atom stuck to the surface of a rock" occurs at all temperatures, including room temperature. Temperature will affect the sticking probability, but the solid/liquid/gas distinction is irrelevant.

b) Keep in mind that "-71C" is merely the point where liquid turns to solid under atmospheric pressure. It does not tell you the vapor pressure of that solid, i.e. how fast the material will sublime. I suspect that solid radon will sublime pretty fast at lunar night-side temperatures (-110C).
 
ben m said:
a) It doesn't count as "solid", in some sense, unless you're talking about more than a monolayer. "One radon atom stuck to the surface of a rock" occurs at all temperatures, including room temperature. Temperature will affect the sticking probability, but the solid/liquid/gas distinction is irrelevant.

b) Keep in mind that "-71C" is merely the point where liquid turns to solid under atmospheric pressure. It does not tell you the vapor pressure of that solid, i.e. how fast the material will sublime. I suspect that solid radon will sublime pretty fast at lunar night-side temperatures (-110C).
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I'm not so sure. First of all, the temperature a few meters down is very constant, although I can't recall it off hand methinks -20C or so. Let's assume that this bad stuff comes up from the deep AT NIGHT. For 330 some hours it condenses at a surface temperature of -110 to -150c in the area of Aristarchus. Then daylight hits. There could be a pretty good layer ready to evaporate quickly. Does this get us the flourescence, such that it could be seen from the Earth? Nope. Unfortunately those anomalies were not correlated with "lunar dawn".

One thing that is clearly different (from the 1/2 meter resolution link above) about this crater compared to many is the steep interior walls that expose the actual rock facing. Most of the lunar features are obscured by regolith, which literally translates to "blanket", some 3-10 meters thick. If radon or other gases were coming up, this would likely do a good job of entrapping them.

Well it's all conjecture. I really have no clue about this.

BenBurch said:
I recall when people thought I was nuts for believing reports of TLPs.
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Depending on who those people were, that could have been confirmation you were right.
 
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