Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

Seventeen stratospherically collected particles-eight of which are classified as interplanetary dust particles (IDPs), seven of which are classified as probable terrestrial contaminants, and two of which have uncertain origins-were studied with a microprobe two-step laser mass spectrometer. Many polycyclic aromatic hydrocarbons(PAHs) and their alkylated derivatives were identified in two of the eight IDPs. The PAHs observed include a high-mass envelope not found in meteorites or terrestrial contaminants and prominent odd-mass peaks suggestive of nitrogen-containing functional groups attached to aromatic chromophores. In addition, the complexity of the IDP mass spectra has no precedence in previous studies of meteorite samples or their acid residues. Extensive checks were performed to demonstrate that the PAH signals are not caused by terrestrial contaminants.

We have developed a mlcroanalytlcal Instrument to analyze the organk constltuonts of partlculates and Inhomogeneous samples wtth aspaUal ramlutbn ol approxlmatdy 40 pm. Om method, two-step laser desorptlon/laser lonlzatlon mass spectrometry (L2MS), uses an Infrared laser to volatlllze constttuent mokuks Intact and an ultraviolet l a w to lonlze desorbed molecules In a selective manner with Imle or no frcrqrwntcrtion. In partlcular, our lnrtrwnent Is currently tuned to detect polycycllc aromatic hydrocarbons (PAHs), whlch have a strong aboorptlon cross section at the lonlzatlon laser wavelength of 266 m. The detection lhnlt of our Instrmnt k approxbnately 6 hnol for the compound wonene (CUH,*). We demonstrate the use of thk Instrument to analyze acld reddues from SIX motrltw the samples cor#kt of particles that are about 200 pm In dlameter. Quantltatlve and qualltatlve trends In PAH comporltlon are IdentHled for different classes of metwrltes. SgnHIcant dMeronces are seen between the carbonaceous and ordlnary chondrftes. Moreover, wlthln a rlngk clam of ordlnary chondrltes we see an Increase h dkybtbn wtth Increasing petrographk type (thennal metamorphlsm).

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