Diversity and similarity of cometsThe evolution of comets from an early stage where they were all similar, to the later diversity is reviewed. The elemental abundances of all pristine comets are likely to be primitive, that is in solar abundance ratios for all elements including C, N, O, S, but with the exception of H (and assumedly He and Ne) that are severely depleted. The solid phase was originally in very fine grains, typically 0.1 micron or less, eventually sintered into larger grain clusters. The volatile phase contains H, C, N, O, and S molecules frozen in the pores of the grain clusters; cosmic ray plus solar irradiation changes the volatile to refractory ratio of the crust. Differences in dust tails, in plasma tails, in photometry between young and old comets, and in the variable carbon depletion of the gas phase seem to be induced by the decay processes.
Document ID
19880012501
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Delsemme, A. H. (Toledo Univ. OH, United States)
Date Acquired
September 5, 2013
Publication Date
September 1, 1987
Publication Information
Publication: ESA, Proceedings of the International Symposium on the Diversity and Similarity of Comets