The present state of knowledge of the chronology of comets -other than that relating to their brief history as visitors to the inner solar system -is limited to conjecture. Primarily it is based on our knowledge of the time of formation of the solar system from meteorite studies coupled with a widespread but not universal belief that comets formed at the same time. The possibility that some carbonaceous chondrites may be samples of cometary cores only weakly supports that view. The possibility that interplanetary dust particles are in part cometary has not helped so far because of the limitations of current dating techniques. The continued development of a wide range of dating techniques and the subsequent application to returned cometary material are important goals relevant to understanding comets.
It is unlikely that the development of remote dating methods will be of sufficient use to justify the effort involved. Bulk in situ measurements of K, Ar, U, and Pb will probably do no more than whet the appetite. The development of remote 4~ dating, using a transuranic neutron source such as 252Cf, is possible but would probably compromise experiments far more appropriate to rendezvous science. The major results from a non-sample-return mission -as far as chronology is concernedwill be a knowledge of the chemical, mineralogical, and petrological state of the cometary surface material from which to prepare the appropriate laboratory techniques for age studies of returned samples.