r-newsComet Chemistry

Hyakutake Produces Another Surprise

Science  31 May 1996:
Vol. 272, Issue 5266, pp. 1263-1264
DOI: 10.1126/science.272.5266.1263


When comet Hyakutake sped past Earth last March, it offered a revelation about comet makeup that is hard to reconcile with standard explanations of how these objects originated. A paper in this issue (p. 1310) reports that sensitive infrared spectroscopy reveals that Hyakutake is rich in methane—a compound expected in comets but never before seen clearly—and in ethane, which was entirely unexpected. Its presence, say researchers, implies that Hyakutake could not have formed from unaltered interstellar material in the primordial cloud that gave birth to the solar system. Instead, Hyakutake and other comets probably formed later, after ultraviolet radiation from the newborn sun had "processed" the ice grains, driving chemical reactions that yielded ethane.