Astrobiology, Comets And the Origin of Life by Chandra Wickramasinghe

By Chandra Wickramasinghe

The concept that comets can be attached with the beginning of lifestyles on the earth was once thought of heresy a couple of a long time in the past, with scientists shying clear of this threat as though from a medieval superstition. but the case that comets can have contributed at the very least the complicated natural construction blocks of existence has develop into very robust, and mechanisms have now been pointed out wherein comets may well incubate and move microbial existence from one cosmic habitat to a different within the Galaxy. The latter strategy cometary panspermia was once pioneered by means of the past due Sir Fred Hoyle and one of many current authors within the early 1980's. A conception that used to be debatable is slowly gaining clinical respectability and aid. the hot surge of curiosity in astrobiology has ended in a spate of books in astrobiology -- combining astronomy and biology -- yet in each one of these, cometary panspermia is handled merely cursorily. the current publication units out the case for cometary panspermia in a cogent manner, combining proof from area technological know-how, celestial mechanics, geology and microbiology. it's going to be an important a part of any collage direction on astrobiology, and in addition function a reference textbook for researchers within the box.

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A tabulation of the principal infrared bands for comparison with the data in Figs. g. , 1993). The column for the biological aromatic ensemble is from the synthesised laboratory spectra obtained by Wickramasinghe et al. (1989, 1990). 46 Astrobiology, Comets and the Origin of Life 6 7 6 7 8 8 9 9 10 10 Fig. , 1999). 3 Distribution of principal infrared emission wavelengths. 5 Cosmic Dust and Life 47 Fig. , 2002). Fig. , 2002). , 2002). The extinction curve for this galaxy is reproduced in Fig. 21, with the dashed curve representing a scattering background attributed to hollow bacterial grains.

Fig. 2 Extinction efficiencies for spherical particles with various values of the refractive index. It is customary to perform calculations for spherical isotropic grains in the belief that a random orientation of irregular-shaped particles can be considered equivalent (as far as extinction goes) to a spherical grain. In order to assess the plausibility of any theoretical dust model we require first to know the relationship between extinction cross-sections of individual grains and the astronomically determined extinction of starlight.

Fig. 3 Interstellar extinction curve in the Galaxy decomposed into 3 components (Hoyle and Wickramasinghe, 1991). The smoothed-out mean extinction curve for the Galaxy from a compilation by Sapar and Kuusik (1978) is shown by the curve marked ‘Obs’ in Fig. 3. 02 µm and/or an unidentified molecular absorber to account for the peak of extinction at 2175A, and (3) dielectric grains of Cosmic Dust and Life 31 radii less than 200A. 6 and k ~ 0 in the visual and near ultra-violet spectral regions. Inorganic ices and silicates are possibilities, but infrared spectra reveal a different story as we shall see.

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