Chemical Abundances of Rock-forming Elements of Cometary Streams Obtained from Meteor Spectroscopy

Introduction: Up to now, only cometary dust from comet 1P/Halley has been analyzed in situ by mass spectrometry techniques. In contrast, numerous studies have been performed in the laboratory over interplanetary dust particles (IDPs) thought to be related to comets. Another discipline that addresses the study of the chemical composition of small meteoroids is meteor spectroscopy, which focuses on the light emitted upon the process of ablation and fragmentation of these particles into the atmosphere due to the high velocity encounter with the Earth. We have derived the relative chemical abundances of Si, Mg, Fe and Ca of eight fireballs belonging to well-known cometary streams (5 Perseids, 1 κ Cignid, 1 Andromedid and 1 Leonid) and compared them to the chemical composition of 1P/Halley dust as well as IDPs. Methods: All spectral records were obtained with fixed cameras (focal length 360 mm, focal ratio 1:4.5) equipped with prisms (resolution 130 Å mm at 4000 Å to 550 Å mm at 6000 Å) or diffraction gratings (resolution 50 Å mm) and registered on 18x24 cm plates (Agfa 100 and Orwo NP27) at the Ondrejov Observatory. As a representative example, figure 1 shows the spectrum recorded for a meteor belonging to the Perseid stream. Each spectrum was corrected from the spectral sensitivity of the spectrograph and plate sensitivity. Data reduction and relative chemical composition of meteoroids were obtained following the procedure developed by Borovicka [1].