Question about J White's moon rock composition

[Al Johnston]

How about the lack of an atmosphere? Even in free fall, an atmosphere could shape a molten droplet into a teardrop. I'd expect a freezing sphere in flight above the moon to come out completely round.

Apparently that's the one shape droplets don't form in an atmosphere

[Luke Pemberton]

There is quite an interesting article on shot towers at Wikipedia and the references therein.

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

[ka9q]

Hey, learn something every day!

[Luke Pemberton]

Hey, learn something every day!

Same here. I would never have thought to look myself. I guess common experience is that we see raindrops run down a window and they have a tear drop shape.

It's a bit like growing up and hearing the phrases 'heat rises' and 'don't let the cold in.' Common language and experience can shape what we think. That's why the CTs fail, the apply their Earth bound experiences to the moon and cannot understand (or in some cases accept) how the evidence is consistent with being in a vacuum at low-g, and subject to billions of years of solar and galatic cosmic radiation.

[Dalhousie]

The teadrop shape of some volcanic glass spherules is a combination of high viscosity compared to water and rapid cooling

[Dalhousie]

That would be good as I knew I had read about convection currents and lunar geology, did a Google seach and found that I had read it on Clavius.

At least I got the attribution right out of my foggy memory.

Maybe this link helps.  It's not exactly where I got the original information, but it is Keller talking about Taylor.
http://cosmoquest.org/forum/showthread.php?40353-How-do-you-fake-moon-rocks/page4

Keller did provide any evidence that lower gravity leaves any impression on the rocks.   As Ross Taylor pointed out to me then and I repeat now, rock crystallisation textures are dominated by the crystallisation forces and crystal dimensions, forces much stronger than gravity.

Magma differentiation is driven by gravity, early crystallising minerals (such as olivine) are denser than the melt settle to thre bottom of the magma chamber.  A few minerals, such as plagioclase, sometimes float, leading to accumulation at the top of the chamber.  So generally large differentiated igneous bodies are more mafic (richer in dark minerals rich in iron and magnesium) at the bottom and more felsic (rich in light-coloured minerals containing silicon, aluminium, calcium etc) at the top. Even asteroids that undergo melting differentiate (which is why we get iron meteorites and the HED family), despite tiny gravitation accelerations.

[BazBear]

Fascinating.

I had read about rain drops not being tear drop shaped some time ago. My question is do other molten materials have surface tension effects similar to water, and if they do, wouldn't the shape of the spherules be indicative of whether they form falling in Earth's atmosphere (more likely to be a more squashed shape) as opposed to the lunar vacuum? Or are spherules simply too small where the atmospheric flattening would be evident?

[JayUtah]

Keller did [not?] provide any evidence that lower gravity leaves any impression on the rocks.   As Ross Taylor pointed out to me then and I repeat now, rock crystallisation textures are dominated by the crystallisation forces and crystal dimensions, forces much stronger than gravity.

And that makes sense to me too.  It would be informative to hear these two hash out their respective views.

[Dalhousie]

Keller did [not?] provide any evidence that lower gravity leaves any impression on the rocks.   As Ross Taylor pointed out to me then and I repeat now, rock crystallisation textures are dominated by the crystallisation forces and crystal dimensions, forces much stronger than gravity.

And that makes sense to me too.  It would be informative to hear these two hash out their respective views.

No going to happen, unless Keller provides a peer reviewed paper to support his view.  Even then, Taylor is now in his 80s. Although still occasionally gives lectures and works on lunar problems.  Even Ross's expertise I would pick his views every time.  People do know who Ross Taylor is I assume.

[Dalhousie]

Fascinating.

I had read about rain drops not being tear drop shaped some time ago. My question is do other molten materials have surface tension effects similar to water, and if they do, wouldn't the shape of the spherules be indicative of whether they form falling in Earth's atmosphere (more likely to be a more squashed shape) as opposed to the lunar vacuum? Or are spherules simply too small where the atmospheric flattening would be evident?

It's a very complex problem, factors such as lava viscosity and surface tension (both reflections of composition) would come into play.  There is also magma temperature, cooling rate, fall time, dynamics of the fire fountain, presence or absence of an atmosphere., and probably others.

[JayUtah]

No going to happen, unless Keller provides a peer reviewed paper to support his view.  Even then, Taylor is now in his 80s. Although still occasionally gives lectures and works on lunar problems.  Even Ross's expertise I would pick his views every time.  People do know who Ross Taylor is I assume.

Keller has peer-reviewed research on similar topics, but I can't find anything suitably specific.  I certainly know who Ross Taylor is, and I think I would lean on his side, given his long, detailed study of lunar minerals.  Keller certainly knows who Taylor is, which makes me wonder why he would disagree without having some basis.  You've convinced me I need to revisit the Clavius page and at least demote Keller's view to a minority.

[Luke Pemberton]

People do know who Ross Taylor is I assume.

Yes, I know who Ross Taylor is. It have read somewhere else that scientists would detect convection currents in fake rocks formed from melts, but (a) I cannot find the source (b) I now defer to your explanations about crystal growth mechanisms and crystal dimensions being dominant. It makes more sense to me. Thanks for your input. It has been most useful in advancing the debate and my understanding. What we can all agree upon is that moon rocks cannot be faked for the other reasons that have been discussed extensively.

[Dalhousie]

One other characteristic of lunar samples not mentioned is that the anorthosites show a positive europium anomaly.  This is due to the enrichment of that element in plagioclase, consistent with plagioclase crystallisation and flotation from a global magma ocean. 

Terrestrial anorthosites do not show such an anomaly.  This could not be predicted without going to the Moon. 

Other lunar mantle-derived rocks have a negative europium anomaly, consistent with derivation from the same magma source as the anorthosites, but depleted in plagioclase.  This planetary-scale would be very hard to fake .

[Luke Pemberton]

One other characteristic of lunar samples not mentioned is that the anorthosites show a positive europium anomaly.  This is due to the enrichment of that element in plagioclase, consistent with plagioclase crystallisation and flotation from a global magma ocean. 

Terrestrial anorthosites do not show such an anomaly.  This could not be predicted without going to the Moon. 

Other lunar mantle-derived rocks have a negative europium anomaly, consistent with derivation from the same magma source as the anorthosites, but depleted in plagioclase.  This planetary-scale would be very hard to fake .

Most useful, thank you.

I've pointed Jarrah in the direction of neutron capture cross sections and asked if he can correlate this with different isotope ratios. No answer yet as he likes to focus on the oxygen isotope similarity that exists between Earth and Moon rocks. Maybe if he understood neutron capture it would explain to him the difference and similarities of the isotope ratios between Moon and Earth rocks. There again, he likes to focus on the similarities, yet has not addressed the differences that would confirm the rocks to be of lunar origin. I guess in short I'm saying he's being deceptive to the point of lying.

[Dalhousie]

If the Earth and Moon formed in the same part of the solar nebula they would be expected to have the same oxygen isotopes.  All three pre-Apollo lunar formation models would have predicted it - the sibling and daughter hypotheses would predict the same ratios, the spouse model may have led to a Moon with different oxygen isotopes, although the most likely orbits for capture would be ones that would again have resulted in similar ratios.

What are you trying to say regarding the neutron capture cross sections?  That is way over my head!