Mathematics – Logic
Scientific paper
Feb 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990plr....10a..20c&link_type=abstract
Planetary Report (ISSN 0736-3680), vol. 10, Jan.-Feb. 1990, p. 20-23, 30.
Mathematics
Logic
Biological Evolution, Earth Atmosphere, Earth Surface, Halley'S Comet, Sea Water, Apollo 11 Flight, Giotto Mission, Marine Chemistry, Organic Compounds, Sea Ice, Earth, Comets, Bombardment, Photographs, Spacecraft Observations, Ice, Organic Material, Composition, Molecules, Grains, Comet Nuclei, Orbits, Impacts, Impact Effects, Water, Abundance, Cratering, Mass, Volume, Source, Origin, Isotopic Ratios, Deuterium, Atmosphere, Halley, Formation, Oceans
Scientific paper
Observations by the Giotto and Vega spacecraft, complemented by observations made on the ground, with sounding rockets and with high-altitude aircraft, verified the long-standing hypothesis that comets consist largely of frozen water. The assumption that comets are loaded with organic molecules, the kind needed for the earliest stages in the evolution of life on earth, was also confirmed. Here the result of a cometary collision with a planet is investigated and it is suggested that, striking the surface of the planet, the comet would excavate a crater and vaporize almost entirely in the ensuing explosion. The comet's steam might form a tenuous atmosphere of water and vapor, or perhaps clouds if the planet already has an atmosphere. The impact of a Halley-type comet would deliver to the surface of the target a certain amount of organics and a great deal of water. Thus it is suggested that water covering the earth today may have originated in comets that condensed in the outer regions of the solar system. Additional examples and depictions are cited to further support this hypothesis. However, if comets brought a significant amount of water to earth, it would be expected that they delivered water to the other planets as well. Comets may also have contributed to the terrestrial inventory of organic molecules necessary for the origins of life. Further perspectives are examined to show that comets may have provided an important extraterrestrial link for the origins of terrestrial life.
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