Elemental and Isotopic Abundances of the Volatile Elements in the Outer Planets (Article published in the Space Science Reviews special issue on 'Outer Solar System Exploration - An Overview', ed. by J. E. Long and D. G. Rea.)

Certain fundamental scientific problems of a cosmological as well as cosmogonic character, may be solved by the insertion of entry probes into the atmospheres of the outer planets. It is recommended that attempts be made to determine the elemental and isotopic abundances of H, D, He³, He⁴, C, N, O, S, and the rare gas elements. These determinations should cast much light on the processes which participated in the assembly of the giant planets. This would give powerful boundary conditions on theories of the origin of the solar system, and would also give additional experimental information bearing on cosmology.