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Gravitational lenses produce multiple images of single astronomical objects. The most widely separated images of a quasar ever found reveal the dark-matter content of the lensing galaxies.
Ken Chien is the director of the Institute of Molecular Medicine at the University of California, San Diego, and a professor in the university's department of medicine and at the Salk Institute (adjunct). His hobbies include wine tasting, oriental art and losing to his daughters at tennis.
Both Mars and Earth have experienced ice ages in geologically recent times. Coincidence of the phenomenon on two planets will further the scientific quest to answer the question of how ice ages originate.