meteorite authentication

[jjjnettie (Jeanette)]

Here's some I collected last year. http://www.iceinspace.com.au/forum/s...cro+meteorites

[jjjnettie (Jeanette)]

from Wiki
Micrometeorites
In 1946, during the Giacobinid meteor shower, Helmut Landsberg collected several small magnetic particles that apparently were associated with the shower.[2] Fred Whipple was intrigued by this and wrote a paper that demonstrated that particles of this size were too small to maintain their velocity when they encountered the upper atmosphere. Instead, they would quickly decelerate and then fall to Earth unmelted. In order to classify these sorts of objects, he coined the term "micro-meteorites".[3]
This early work, in collaboration with Fletcher Watson, led the Harvard Observatory to build a station observatory to directly measure the velocity of the meteors that could be seen. At the time some argued that meteors were extra-solar in origin, while others claimed they were leftovers from the formation of the solar system. These direct measurements were able to locate the source of the meteors, demonstrating that the bulk of material was leftover from comet tails, and that none of it could be demonstrated to have an extra-solar origin.[4] Today it is understood that meteors of all sorts are leftover material from the formation of the solar system, part of the interplanetary dust cloud or the various other objects made up from this material, like comets.[5]
These studies were based on optical measures only. In 1957 Hans Pettersson conducted one of the first direct measurements of the fall of space dust on the Earth, estimating it to be 14,300,000 tons per year.[6] If this were true, then the meteor flux in space was much higher than what the telescopes were seeing. If true, meteors would present a very serious risk to missions deeper in space, specifically the high-orbiting Apollo capsules. To determine which measure was more accurate, a number of additional studies followed, including the Pegasus satellite program. These showed that the flux in line with the optical measures, around 10,000 to 20,000 tons per year.[7]

That's a hell of a lot of debris falling from the sky each day.

[AstralTraveller (David)]

If Steve is right and Neodymium magnets can pick up hematite then I'll punt for bits of broken up laterite. It's widespread in Oz and given the age of the soils on the EP there's bound to be plenty there. Add a bit of farm machinery to break it up and Bob's your uncle.

Have you looked at them under a magnifying glass? Laterite can develop a good approximation of a 'fusion crust' but you should be able to see entrapped quartz grains somewhere. Laterites also tend to be mottled but I imagine that will be difficult to see on such small fragments. Another easy test would be to measure the density. You probably have all the equipment lying around (something to weigh one and something to measure the volume of water displaced). You'll need to check but I believe the density of metalic/stoney of meteorites would be quite high (sg > 4 perhaps) whereas I'd guess that laterite is about 2.5.

The "home-style nickel detector" is a hand-held X-ray fluorescence spectrometer (XRF). eg http://www.bruker-axs.com/handheldpr...XRF%20analysis
http://discover.asdi.com/new-handhel...FQbbbgodFlmZ_A
They seem to be the bees knees for portable non-destructive analysis. At work the archaeologists are keen on one to do things like analysis of the 'paint' used in cave paintings. They would need to top-of-the range model and I think I heard $50k mentioned. So you could probably pick up a basic metal-assay model for the cost of one or two SDMs .

[sjastro]

Originally Posted by CraigS

As an example, if I was to go and stick a magnet into the dirt outside my house, I'd end up with the magnet being heavily covered in what would probably amount to 'iron filings' (after analysis). I have no idea what the source really is .. but the evidence exists.

How can I pick out the samples (for analysis) from all of that?

We need a home-style nickel detector !

Cheers

I'd use a microscope. I suspect micrometeorites are more rounded in shape, iron filings would have sharper edges.

Larger pieces such as slag are identified by a lack of fusion crust.

Regards

Steven

[CraigS]

Ok JJJ, Astroron and Suzy;

I'm not saying that micrometeorites don't exist ! After all, the entire Earth was some kind of meteor, at some stage !!
All I'm saying is that rooftops gather a lot of other contaminants, which would require separation by some, (several) means, before sending it off to a lab.

Depending on your location (remember there are lots of us who live in cities), you'd have to consider the history of the collection site.

David: Cool instrument .. that, and a microscope is what I'm talkin' about !

Cheers
PS: Does anyone know what the lab analysis costs ?

[AstralTraveller (David)]

Originally Posted by jjjnettie

from Wiki
... around 10,000 to 20,000 tons per year.[7]

That's a hell of a lot of debris falling from the sky each day.

The surface area of the Earth is 510,072,000 km2. If we assume 20,000 tonnes of meteorites p.a. distributed evenly then the rate of fall is 0.00003921 tonnes per km2 per year or 0.00003921g/m2 per year. I regularly weigh out 40 micro-gram samples of calcium carbonate and that is about 6 specks on the end of the micro-spatula. Given that meteorites are denser than calcium carbonate you are down to about 3-4 specs. Alternatively that is one milligram size particle every 100m2 per year. Of course micrometeorites have been raining down for a very long time but they also would weather away in the soil so I expect the density would remain very low. Micrometeorites are out there and we can all collect them but don't expect to trip over one; and not every interesting-looking spec has to be a micrometeorite.

[jjjnettie (Jeanette)]

That's so true.
The ones I found were sorted out of many dozens of samples from my sieve.
I used macro photography to examine them closer.
There is a great book on the subject, "A Field Guide to Meteors and Meteorites" by O. Richard Norton and Lawrence A Chitwood.
I highly recommend it.
http://www.springer.com/astronomy/as...-1-84800-156-5

[AstralTraveller (David)]

Thanks for pointing out that book. It looks good and I've just ordered a copy.

[Lester]

I did not get a reply to my email, so I guess that means they are just Earthly rocks. Some reply would have been good. Hope others have more luck.