Meteoritics - Science topic

Do you know Dr. Steven Greer? Have a look at internet, Netflix, etc...

The original composition of micrometeorites is lost due to atmospheric entry heating in most cases, e.g. in cosmic spherules and scoriaceous micrometorites. However i) some micrometeorites classified as "unmelted" preserve the original composition of the micrometeoroid and ii) although melting and evaporation is important in cosmic spherules and scoriaceous micrometeorites, the original composition of their micrometeoroid can be inferred based on geochemical and mineralogical combined studies (e.g. the study of the relic mineral phases they contain, oxygen isotope bulk composition, etc. see Folco and Cordier (2015, EMU Notes in Mineralogy) for a recent review. 

Dear David,

A lot of literature exists dealing with the topic you are interested in. Here are just a few examples:

French, B.M. (1998). Traces of Catastrophe. Lunar and Planetary Institute. Retrieved 2007-05-20.

ANN M. THERRIAULT – RICHARD A. F. GRIEVE – MARK PILKINGTON. The recognition of terrestrial impact structures. Bulletin of the Czech Geological Survey, Vol. 77, No. 4, 253–263, 2002.

B.M. French and C. Köberl. The convincing identification of terrestrial meteorite impact features: What works, what doesn’t, and why. Earth-Science Reviews 98(1):123-170 · January 2010.

and many others...

I assume, you are searching for literature on terrestrial impact structures. I recommend the following page:

On this page, you can find the most important literature available for each (confirmed) terrestrial impact crater you are interested in.

By the way, rocks hit by an asteroid are not neccessarily vaporized, These rocks can also be melted (impact mekt breccias or Impact melt rocks) or just brecciated (impact breccias).

All the best

Elmar

Dear Sebastian,

at the beginning of a possible discussion I will kindly ask you for more information, eg. which type of meteorites do you mean? Is this obviously empiric observation restricted to meteorites? - from my evaluation und understanding of deterioration processes I have to say clearly NO.

One simplified answer could be:

In arctic regions the number of the essential frost-thaw cycles  is significant lower than in temperate regions. The more frost-thaw cycles (physical weathering) appear the faster the fabric of rocks will disintegrate.

Under more or less dry desert climate humidity derieving more or less only from condensation processes penetrates the porosity and the progress of deterioration will be delayed, due to the small quantity of water. Therefore chemical alteration is delayed too. The influence of thermic induced dilatation, due to the daily difference of temperature between day and night is in the case of meteorites  even small because these meteorites are not as volumious as eg. outcropping bedrock, which will be effected very strong.

Strong chemical weathering (alteration and dissolution) appear in humid tropical regions.

Temperate climates with frost-thaw cycles show both types of weathering, chemical and physical in respect to the microclimatic exposition.

Attached you will find some basic informations - maybe they are helpful

best regards

Andreas

BERTA, S. (2005): Geomorphology and Climate. – John E. Oliver Encyclopedia of Earth Sciences Series Encyclopedia of World Climatology,10.007/1-4020-3266-8_87© Springer.

Tungsten isotopes are novel in studying the core formation events at planetary bodies. However, for knowing the extra-terrestrial contribution, triple oxygen isotope study on potential samples may provide you some info.

Alexander Bagrov writes that a collision of two Lunar-sized bodies will not result in the release of fragments since they will be gravitationally bound. Although this is certainly true - it is not a problem for our understanding of the origin of differentiated meteorites from asteroids. Cooling rates of iron meteorites range from 1-1000 K/My. These cooling rates constrain the cooling rate of the asteroid core shortly after it crystallized. Since largfe asteroids cool slower than small asteroids they may be used to infer sizes of asteroids. Diameters were genererally less than 50 km - much smaller than the Moon - and sufficiently small that it is not a problem to catastrophically destroy them.

We know that fragments of asteroids escape our Solar System and it thus follows that fragments must also escape other Solar System provided they include minor bodies. It should therefore be possible to find an extrasolar rock in our Solar System. Unfortunately, it is unlikely that it will heat our atmosphere slowly enough to survive. Also, the frequency of such a fall makes it unlikely that we will ever observe it or even find an old extrasolar meteorite fall here on Earth. I have seen an estimate concluding that we should expect a extrasolar meteorite fall here on Earth every 10 billion years.

In other words, extrasolar meteorites are not impossible but the exceedingly low fall rates makes it less than likely that we will ever come across one.

If we were ever to find one there is no doubt that we be able to tell that it is extraolar - it would be different in terms of bulk chemistry, isotope chemistry and its ages would be way off anything we have seen before.

Oh, then I misunderstood your question (and again learned something new) - thank you for the paper. :)