Schirra, Glenn, and Scott Carpenter are the last remaining Mercury astronauts. Virgil "Gus" Grissom died in the Apollo 1 fire in 1967; Donald K. "Deke" Slayton died in 1993 of brain cancer; and Alan Shepard Jr. died of leukemia in 1998. In April 1959, Cooper was chosen as a Mercury astronaut. He died in July 1962 when his Vostok spacecraft crashed on its return to Earth. The only surviving member of the first group of astronauts is Gordon Cooper. He retired in 2004 after 44 years with NASA, most recently working from Houston as director of flight operations. The other members of this group are dead. Of the remaining astronauts, only three (Schirra, Glenn, and Carpenter) were alive when the Space Shuttle program began in 1981. They all flew on one mission: OA-3, which lasted 10 days and 10 hours and carried supplies for the International Space Station (ISS). Since then, Schirra has died, Glenn has retired, and Carpenter has stayed on at NASA until now. The only other man who has flown in space twice is Mike Hopkins, but he didn't count toward the six because his first trip was as part of the Russian crew of Soyuz 19 in 1975. There are currently only 12 people on Earth who have walked in space: five Russians and seven Americans.