The Soviet state media attempted to downplay the tragic end of the mission and instead emphasized its accomplishments during the crew's stay aboard Salyut 1. Since they did not publicly announce the exact cause of the cosmonauts' deaths for almost two years afterwards, United States space planners were extremely worried about the upcoming Skylab program, as they could not be certain whether prolonged time in a micro-g environment had turned out to be fatal. However, NASA doctor Charles Berry maintained a firm conviction that the cosmonauts could not have died from spending too many weeks in weightlessness. Until the Soviets finally disclosed what had really happened, Dr. Berry theorised that the crew had died from inhaling toxic substances.