Presolar grains

Presolar minerals, often called presolar grains or star dust, tiny crystals are part of the fine-grained matrix of primitive meteorites and existed before the formation of our solar system.

It is believed that they originated in supernova explosions or around red giant stars. They were later part of those molecular cloud from which ultimately separated the solar nebula and collapsed to our solar system. The collapse of the solar nebula and the subsequent formation of planetesimals from which descended the primitive meteorites, they probably have survived because they are made of tough, so-called refractory minerals.

There are different types of presolar crystals were of which have been identified the following:

• Diamond (C )
• Graphite (C )
• Silicon nitride ( Si3N4)
• Corundum ( Al2O3)
• Spinel ( MgAl2O4 )
• Hibonite ( (Ca, Ce) (Al, Ti, Mg) 12O19 )
• Rutile ( TiO2)

In the mid- 1960s, rare gases have been found with unusual isotopic ratios in primitive meteorites. This has already led then to the conclusion that there are presolar minerals that act in these meteorites as a carrier of these rare gases. But only in 1987 was tiny diamond and silicon carbide grains are identified as carriers. Since the solar matter has a reasonably homogeneous isotopic composition, prove the additional isotopic anomalies discovered in the minerals the presolar origin of these unusual crystals.

Presolar diamonds have only a size of a few nanometers, which is why they are also called nanodiamonds. Although nanodiamonds, in addition to silicon carbide crystals, the crystals were first discovered presolar, relatively little is known about them. The remaining pre-solar crystals have a typical size in the micrometer range and are therefore easier to examine.

Presolar crystals are mainly through

• Electron microscopy ( SEM / TEM) and
• Mass spectrometry ( noble gas mass spectrometry, resonance ionization mass spectrometry ( RIMS), secondary ion mass spectrometry (SIMS, NanoSIMS ) )

Examined.