The disclosure meeting ... an alien artifact is discovered in the moon.
Contact with the unknown.
18-Months Later... A mission to Jupiter is sent to seek out extraterrestrial intelligence near the moon Io.
"Eighteen months ago the first evidence of intelligent life off the Earth was discovered. It was buried 40 feet below the lunar surface near the crater Tycho. Except for a single very powerful radio emission aimed at Jupiter the four-million year old black monolith has remained completely inert. Its origin and purpose are still a total mystery..." - Dr. Heywood Floyd, National Committee for Aeronautics.
From Europa, the sole survivor of the failed mission to Jupiter is taken through a Star Gate from another Monolith.