There was a peculiar sensation of the duality of time — the swift rush of events that characterizes all our lives — and the ponderous parade which marks the aging of the universe. Both kinds of time were evident — the first, by the routine events of the flight, whose planning and execution were detailed to fractions of a second — the latter by rocks around us, unchanged throughout the history of man — whose 3-billion-year-old secrets made them the treasure we sought.