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Luna 16's flight should pay handsome scientific dividends. The Sea of Fertility is thought to be one of the oldest lunar maria, and the soil that was retrieved from below its surface could yield important clues to the early history of the moon. The successful mission also rekindled the old debate about relative merits of manned v. unmanned exploration of space. Although the two U.S. manned lunar landing missions brought back 130 Ibs. of moon rock and performed a number of other important scientific experiments, Soviet commentators asserted that unmanned spacecraft could be built to perform many of those tasks at 1/20 to 1/50 the cost and at no risk to human life. In fact, Luna 16's triumphant return makes it more probable that an unmanned craft will bring back samples of soil and rocks from Mars long before the first astronauts—or cosmonauts —land there.