Meteorites micrometeorites

Organic-rich extraterrestrial samples such as meteorites, micrometeorites, interplanetary dust particles (IDPs) and samples returned by spacecraft provide a unique record of the chemical processes in the early solar system and in the interstellar medium. In particular, detailed structural and isotopic analyses of carbonaceous meteorites have revealed a rich organic inventory and provided evidence of the synthesis of complex organic molecules in the interstellar medium and on the asteroidal parent bodies of meteorites [1,2], The organic matter in carbonaceous meteorites is present at levels of up to 5% and can be divided into solvent-soluble (l%-25%) and insoluble (75%-99%) fractions, the former characterized by considerable structural, isomeric, and isotopic diversity [2,3], and the latter characterized by a high molecular weight and complex aromatic network [4]. 

The number of scientific articles published on meteorites has increased dramatically in the last few years few of these, however, concern themselves with small meteorites, the size of which lies between that of the normal meteorites (from centimetres to metres in size) and that of interplanetary dust particles. In the course of an Antarctic expedition, scientists (mainly from French institutions) collected micrometeorites from 100 tons of Antarctic blue ice (Maurette et al 1991). These micrometeorites were only 100 400 pm in size five samples, each consisting of 30-35 particles, were studied to determine the amount of the extraterrestrial amino acids a-aminoisobutyric acid (AIBS) and isovaline—both of which are extremely rare on Earth—which they contained. The analysis was carried out using a well-tested and extremely sensitive HPLC system at the Scripps Institute, La Jolla. Although the micrometeorites came from an extremely clean environment, the samples must have been contaminated, as they all showed traces of L-amino acids. Only one sample showed a significantly higher concentration of AIBS (about 280 ppm). The AIBS/isovaline ratio in the samples also lay considerably above that previously found in CM-chondrites. 

Engrand C. and Maurette M. (1998). Carbonaceous Micrometeorites from Antarctica (Invited Review). Meteorites and Planetary Science 33 565-580... 

In addition to meteorites, three other important types of extraterrestrial material are available for analysis interplanetary dust particles (IDPs), micrometeorites, and Stardust samples. Interplanetary dust particles are collected in the stratosphere by high-altitude research aircrafts. Most of these samples are smaller than 20 pm in diameter, although some of the highly porous cluster particles probably exceeded... 

Presolar grains are found in small quantities (with concentrations of ppb to several 100 ppm, see Table 2.1) in all types of primitive Solar System materials (Lodders Amari 2005 Zinner 2007). This includes primitive meteorites (the chondrites), IDPs, some of which might originate from comets, Antarctic micrometeorites (AMMs), and samples from comet Wild 2 collected by NASA s Stardust mission. Presolar grains are nanometer to micrometer in size. The isotopic compositions, chemistry, and mineralogy of individual grains with sizes >100 nm can be studied in the laboratory. Important analysis techniques are secondary ion mass spectrometry (SIMS) and resonance ionization mass spectrometry (RIMS)... 

Matrajt G, Pizzarello S, Taylor S, Brownlee D. Concentration and variability of the AIB amino acid in polar micrometeorites Implications for the exogenous delivery of amino acids to the primitive Earth. Meteorit. Planet. Sci. 2006 128 7412-7413. Busemann H, Young, AE, Alexander, CMO D, Hoppe, P, Mukhopadhyay, S, Nitter, LR. Interstellar chemistry recorded in organic matter from primitive meteorites. Science 2006 312 727-730. 

Greshake A., Hoppe P., and Bischoff A. (1996) Mineralogy, chemistry, and oxygen isotopes of refractory inclusions from stratospheric interplanetary dust particles and micrometeorites. Meteorit. Planet. Sci. 31, 739-748. 

Schramm L. S., Brownlee D. E., and Wheelock M. M. (1989) Major element composition of stratospheric micrometeorites. Meteoritics 24, 99-112. 

Kldck W. and Stadermann F. J. (1994) Mineralogical and chemical relationships of interplanetary dust particles, micrometeorites and meteorites. In Analysis of Interplanetary Dust, AIP Conf. Proc. 310 (eds. M. E. Zolensky, T. L. Wilson, and F. J. M. Rietmeijer). Am. Inst. Phys., New York, pp. 159-164. 

Love S. G. and Brownlee D. E. (1996) Peak atmospheric entry heating temperatures of micrometeorites. Meteorit. Planet. Set 31, 394-402. 

Engrand, C. Maurette, M. 1998. Carbonaceous micrometeorites from Antarctica. Meteoritics and Planetary Science, 33, 565-580. 

Rietmeijer, F.J.M. Interrelationships among meteoric metals, meteors, interplanetary dust, micrometeorites, and meteorites. Meteoritics Planet. Sci. 2000, 35. 1025-1041. 

Ellison DC, Druiy LO C, Meyer J-P (1997) Galactic cosmic rays from supernova leumants. 11. Shock acceleration of gas and dust. Astrophys J 487 197-217 Engrand C, Maurette M (1998) Carbonaceous micrometeorites from Antarctica. Meteoritics Planet Sci 33 565-580... 

Space erosion. It is conceivable that meteoroids change their shape not only by a macroscopic collision but by continuous erosion by micrometeorites in space. This space erosion has occasionally been invoked to explain discrepant exposure ages based on various nuclide systems. However, no generally accepted space erosion rates appear to have been derived and space erosion is not routinely taken into account when deducing exposure ages of meteorites. Voshage (1984) estimated space erosion rates on the order of 0.1 mm/Myr for iron meteorites by comparing the minimum depths of iron meteorite... 

---