Meteorite has expert stumped.

sjastro · Mar 31, 2021

I was able to obtain a meteorite sample from Bassikounou in Mauritania.

Bassikounou 15°47'N, 5°54'W
Bassikounou, Hodh Ech Chargui, Mauritania

Fall: 16 October 2006; 04:00 UTC
Ordinary chondrite (H5)

History: A fireball was witnessed in the area, but no records of the direction of movement were recorded. A single stone of 3165 g was found by A. Salem El Moichine, a local resident, on the same day at 13:00 hr local time, 11 km SE of Bassikounou. The sample for classification was provided to NMBE by M. Ould Mounir, Nouakchott, who obtained it from his cousin who recovered the meteorite. According to S. Buhl (Hamburg, Germany), more than 20 specimens were later recovered by locals and meteorite finders. These finds define a 8 km long strewnfield. The total recovered mass is 46.00 kg.

Physical characteristics: The 3165 g specimen is largely covered by black fusion crust. The interior is light gray. On the surface of the fusion crust there is some adherent soil material, some of which is bright red. Shortly after recovery, the stone was cut into two pieces of 1200 and 1950 g. The larger piece has a rectangular shape and shows indications of flow-lines in the fusion crust.

Petrography: (E. Gnos, MHNGE; B. Hofmann, NMBE, M. Eggimann, Bern/NMBE): Mean chondrule size 0.35 mm (n=53). Metal abundance is 8 vol%, troilite 6.6 vol%. Mean plagioclase grain size is ~20 mm. Troilite is polycrystalline, rich in silicate inclusions, and shows diffuse boundaries to metal. Metal is partly rich in silicate- and troilite inclusions. Rare metallic Cu (10 mm) occurs at kamacite-taenite boundaries and in troilite. Some shock veins and no weathering products were observed.

Mineral compositions: Olivine (Fa18.6), pyroxene (Fs16.3 Wo1.1), plagioclase (An13.7).

Cosmogenic radionuclides: (P. Weber, PPGUN) Gamma-spectroscopy performed in December-January 2006 showed the presence of the following radionuclides: 48V, 46Sc, 56Co, 54Mn, 58Co, 7Be, 51Cr, 57Co, 22Na, 26Al and 60Co. Recalculated to 12 October 2006 22Na was 38.0±2.2 and 26Al 31.5±2.1 (both dpm/kg), the activity ratio of 1.21 is fully consistent with a fall on that date.

Classification: Ordinary chondrite (H5); S2, W0.

Type specimens: A total of 115 g are on deposit at NMBE. Boudreaux holds the main mass.

I took images in ordinary light and longwave UV at 365nm.

Plus a microscopic image of the fluorescent crystals under longwave UV.

I'm clueless as to why the meteorite is fluorescent given its composition so I sent the images to Randy Korotev at Washington Uni. who is a world renowned expect on meteorites.

This was his response.

Randy Korotev said:
I do not know the answer to your question.

Typically Randy gave a no nonsense, non rambling response.

SelfSim · Mar 31, 2021

Well that makes me feel a whole lot better .. after your mystery coin flourescence thread!

You must be a pioneer in flourescent imaging .. however, its a bit hard to swallow that, I suppose, when they're sending probes out to Mars which specifically make use of the technique(?)
Perhaps sending the (Mars) imaging folk a more general query about where we can go to learn up more on how they expect to interpret any specific 'glows' they might find?

sjastro · Mar 31, 2021

SelfSim said:
Well that makes me feel a whole lot better .. after your mystery coin flourescence thread!

You must be a pioneer in flourescent imaging .. however, its a bit hard to swallow that, I suppose, when they're sending probes out to Mars which specifically make use of the technique(?)
Perhaps sending the (Mars) imaging folk a more general query about where we can go to learn up more on how they expect to interpret any specific 'glows' they might find?

It's only been in the past few years LED UV torches have come onto the market which have a compatible performance with UV lamps.
The LED torch I use plus a link to fluorescent meteorites is found here.

The only pitfall I have encountered is imaging through a microscope.
Initially my images came out a purplish red colour.
It finally dawned on me UV light reflected off the sample was reaching the camera sensor and destroying the colour balance.
Unlike camera lenses which have a UV coating, microscope optics are uncoated.
I found a UV rejecting filter used for astrophotography inserted between the camera and microscope optics an effective countermeasure.

SelfSim · Mar 31, 2021

I think there's only one way to resolve this to be sure .. I think the entire sample should be completely pulverised until its a very fine powder, and then oxygenated by standing what's left, in front of a very strong fan, such that it blows away the whole problem?!

That should resolve the matter, no?

sjastro · Mar 31, 2021

SelfSim said:
I think there's only one way to resolve this to be sure .. I think the entire sample should be completely pulverised until its a very fine powder, and then oxygenated by standing what's left, in front of a very strong fan, such that it blows away the whole problem?!

That should resolve the matter, no?

That's equivalent to pulverizing the money I spent on the sample.

Yttrium · Apr 1, 2021

Is it possible that the flourescents embedded into the meteorite on impact?

sjastro · Apr 1, 2021

Yttrium said:
Is it possible that the flourescents embedded into the meteorite on impact?

On one side of the sample the black fusion crust has broken off.
The fusion crust is formed when the surface of the meteorite melts due to atmospheric friction and solidifies on cooling.

The luminous 'threads' in the UV image is due to external dust contamination but the fluorescence seems to be confined to the fusion crust.
The most likely explanation is that the fluorescent crystals have formed when the fusion crust has cooled and solidified and is therefore part of the composition of the meteorite.

Petros2015 · Apr 1, 2021

Huh.

Maybe it's a Mood Meterorite.
What happens if you talk angry to it? Does the color change?

Petros2015 · Apr 1, 2021

Huh.

Maybe it's a Mood Meterorite.
What happens if you talk angry to it? Does the color change?

SelfSim · Apr 1, 2021

sjastro said:
The luminous 'threads' in the UV image is due to external dust contamination but the fluorescence seems to be confined to the fusion crust.
The most likely explanation is that the fluorescent crystals have formed when the fusion crust has cooled and solidified and is therefore part of the composition of the meteorite.

Maybe atmospheric (mineral) dust particles formed part of the fusion crust during the heating phase .. (but I'd bet the interior produces the same fluorescence).

What's wrong with saying the fluorescent material may have been part of the original rock formation process (or at least following up on that)?

sjastro · Apr 1, 2021

SelfSim said:
Maybe atmospheric (mineral) dust particles formed part of the fusion crust during the heating phase .. ..

If this was the case one can argue that fluorescent meteorites should be common and not only confined to stony meteorites (as per the sample) but also to stony-irons and iron meteorites.

A clue is the size of the fluorescent crystals.
With the exception of the two large crystals pictured, the crystals are microscopic indicating cooling was rapid during their formation.

What's wrong with saying the fluorescent material may have been part of the original rock formation process (or at least following up on that)?

That's what I have been saying all along.

SelfSim · Apr 1, 2021

sjastro said:
A clue is the size of the fluorescent crystals.
With the exception of the two large crystals pictured, the crystals are microscopic indicating cooling was rapid during their formation.

Hmm .. so that might have happened when it was blasted off the parent body and suddenly found itself in the cold of open space then, eh?

sjastro · Apr 1, 2021

SelfSim said:
Hmm .. so that might have happened when it was blasted off the parent body and suddenly found itself in the cold of open space then, eh?

Once in space basically nothing.
The composition of the meteorite depends on the type of asteroid being impacted and the region of the asteroid where the fragments originate.

A fragment from a type S asteroid for example, if from the core which reaches the Earth is an iron meteorite; from the mantle-core boundary a Pallasite or stony-iron meteorite; and from the crust a stony meteorite.

SelfSim · Apr 2, 2021

Hmm I clearly need some refreshers on my meteor/asteroid theory, eh?

So some papers on chondritic meteorites mention that some may show signs of having been exposed to water/ice at some stages(?) .. Maybe that would influence mineralisation?

sjastro · Apr 2, 2021

SelfSim said:
Hmm I clearly need some refreshers on my meteor/asteroid theory, eh?

So some papers on chondritic meteorites mention that some may show signs of having been exposed to water/ice at some stages(?) .. Maybe that would influence mineralisation?

Chondrite meteorites are composed of chondrules which are molten or partially molten droplets of matter formed before the accretion stage of an asteroid.

The order of events are chondrules → accretion → asteroid formed → impact with asteroid → meteoroids → chondrite meteorite reaches Earth.

Along with chondrules are refractory inclusions which are the oldest materials known.
The silicon carbide inclusions found in the Murchison meteorite is far older than the solar system around 7.5 billion years old.

Larniavc · Apr 2, 2021

sjastro said:
I was able to obtain a meteorite sample from Bassikounou in Mauritania.

I took images in ordinary light and longwave UV at 365nm.

Plus a microscopic image of the fluorescent crystals under longwave UV.

I'm clueless as to why the meteorite is fluorescent given its composition so I sent the images to Randy Korotev at Washington Uni. who is a world renowned expect on meteorites.

This was his response.

Typically Randy gave a no nonsense, non rambling response.

A quick google search shows UV fluorescent minerals are not uncommon.

sjastro · Apr 2, 2021

Larnievc said:
A quick google search shows UV fluorescent minerals are not uncommon.

This is well documented as shown on this site.
The composition of the Bassikounou meteorite however does not contain any of these minerals.

SelfSim · Apr 2, 2021

sjastro said:
This is well documented as shown on this site.
The composition of the Bassikounou meteorite however does not contain any of these minerals.

I was thinking (in the 'coin' thread) that the tolerances of the UV source (or even the filters/camera CCD) may not be of the same standard as the apparatus/methods used by the people who ascertained the composition of the main body meteorite(?) That might explain the same apparent effect being present in both your coin test .. and now in this meteorite test(?)

So, maybe it just looks to be flourescence, but maybe it isn't(?) (Its sorta hard to tell from looking at the images .. it may be more obvious for you doing the test though .. so I'd defer to your more direct calls/eyeballing on that front).

PS: (I'll bet you've already checked all that out already though .. I'm not inferring a lack of thoroughness on your part here .. more like manufacturing issues/variances/mismatches of the various setup bits and pieces ..? I'm always skeptical about the engineers/product managers who produce these gizmos .. )

sjastro · Apr 2, 2021

SelfSim said:
I was thinking (in the 'coin' thread) that the tolerances of the UV source (or even the filters/camera CCD) may not be of the same standard as the apparatus/methods used by the people who ascertained the composition of the main body meteorite(?) That might explain the same apparent effect being present in both your coin test .. and now in this meteorite test(?)

So, maybe it just looks to be flourescence, but maybe it isn't(?) (Its sorta hard to tell from looking at the images .. it may be more obvious for you doing the test though .. so I'd defer to your more direct calls/eyeballing on that front).

PS: (I'll bet you've already checked all that out already though .. I'm not inferring a lack of thoroughness on your part here .. more like manufacturing issues/variances/mismatches of the various setup bits and pieces ..? I'm always skeptical about the engineers/product managers who produce these gizmos .. )

In the coin thread the material was visible at λ = 254nm shortwave UV, not at λ = 365nm longwave UV.
This is a demonstration of quantum mechanics at work.
Whatever this material is photons at an energy E = h/λ where absorbed by the material sending electrons into higher energy levels.
On returning to the ground state visible light or fluorescence is observed.

The same mechanism applies to meteorites.
When it comes to longwave UV equipment the bandwidth of the emitted radiation is an important factor.
If it is too wide it can extend into the visible light region ≈ 400nm and one cannot be certain if fluorescence or reflected visible light is observed.
The measured radiation for the longwave UV torch I use indicates this is not a problem.

For extra insurance the torch comes with a light rejection filter in the 400 - 700 nm range which was also tested.

The only issue as I mentioned previously is too make sure reflected UV light does not reach the CMOS sensor of the camera which is UV sensitive.
This is not a problem with camera lenses which are coated, the microscope optics required the use of a UV rejection filter to work.

A good example is a suspect meteorite in my possession which Randy Korotev wanted tested is shown in the visible light vs longwave UV comparison microscopic image.

There is absolutely no doubt in my mind the Bassikounou sample is fluorescent under longwave UV.

sjastro · Apr 2, 2021

From the Bassikounou sample is a microscopic image of a spherule possibly a 4.5 billion year old chondrule.

Only Pb-Pb dating will verify this.

Chondrules and calcium–aluminium-rich inclusions (CAIs) are spherical particles that make up chondritic meteorites and are believed to be the oldest objects in the solar system. Hence precise dating of these objects is important to constrain the early evolution of the solar system and the age of the earth. The U–Pb dating method can yield the most precise ages for early solar-system objects due to the optimal half-life of 238U. However, the absence of zircon or other uranium-rich minerals in chondrites, and the presence of initial non-radiogenic Pb (common Pb), rules out direct use of the U-Pb concordia method. Therefore, the most precise dating method for these meteorites is the Pb–Pb method, which allows a correction for common Pb.[3]

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