Two enduring mysteries from the 1960s came closer to being solved in the past year with the discovery of astronaut Gus Grissom's space capsule, Liberty Bell 7 (being raised at right), in July 1999 and the Israeli submarine Dakar in May.The seas recently have given up two secrets—at least partially so. After lengthy searches, the Mercury capsule flown by the second American to fly in space and an Israeli submarine lost with all hands have been located on the ocean floor.