Nitrogen

The measurements performed until 2000 indicated a low concentration of this element, which was near the limit of sensitivity (about 0.1%) of our technique of electron energy loss spectroscopy in a high voltage electron microscope. With this limit, only a few AMMs gave a weak signal above background around 400 eV, which was too small to be quantified. Thus the upper limit of the nitrogen content of AMMs is approximately 0.1%. Recently, Matrajt et al. (2001) measured the C and N contents of both AMMs and two HCCs

Fig. 3.2. A beam of deuterons was used in a nuclear microprobe to get the mi-cromappings of the carbon and nitrogen concentrations in a fine-grained Antarctic micrometeorite collected at Cap-Prudhomme (top), throughout the 12C(d,po)13C and 14N(d,p0)15N reactions. The C and N concentrations are clearly correlated. They yield average values of the N/C ratio ranging from about 20 to 40. This indicates that the dominant C-rich component of micrometeorites is related to "kerogen." (Courtesy of J.P. Gallien and G. Matrajt).

Fig. 3.2. A beam of deuterons was used in a nuclear microprobe to get the mi-cromappings of the carbon and nitrogen concentrations in a fine-grained Antarctic micrometeorite collected at Cap-Prudhomme (top), throughout the 12C(d,po)13C and 14N(d,p0)15N reactions. The C and N concentrations are clearly correlated. They yield average values of the N/C ratio ranging from about 20 to 40. This indicates that the dominant C-rich component of micrometeorites is related to "kerogen." (Courtesy of J.P. Gallien and G. Matrajt).

relying on a nuclear microprobe with a much improved lower limit of detection (Fig. 3.2). The minimum nitrogen content of micrometeorites was thus found to be approximately 0.03%.

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