The nature and origin of interstellar diamond.
Microscopic diamond was recently discovered in oxidized acid residues from several carbonaceous chondrite meteorites (for example, the C delta component of the Allende meteorite).  Some of the reported properties of C delta seem in conflict with those expected of diamond.  Here we present high spatial resolution analytical data which may help to explain such results.  The C delta diamond is an extremely fine-grained (0.5-10 nm) single-phase material, but surface and interfacial carbon atoms, which may comprise as much as 25% of the total, impart an 'amorphous' character to some spectral data.  These data support the proposed high-pressure conversion of amorphous carbon and graphite into diamonds due to grain-grain collisions in the interstellar medium although a low-pressure mechanism of formation cannot be ruled out.
Blake
D F
DF
NASA Ames Research Center, Moffett Field, California 94035, USA.
Freund
F
F
Krishnan
K F
KF
Echer
C J
CJ
Shipp
R
R
Bunch
T E
TE
Tielens
A G
AG
Lipari
R J
RJ
Hetherington
C J
CJ
Chang
S
S
D002244:Carbon / Q000737:chemistry*; D018130:Diamond / Q000032:analysis*; D019418:Evolution, Chemical; D018559:Exobiology; D005118:Extraterrestrial Environment; D019110:Meteoroids; D008855:Microscopy, Electron, Scanning; D016082:Solar System
D002244:Carbon; D018130:Diamond