On July 8, 1947, a press release from the Roswell (New Mexico) Army Air Field noted the recovery of a crashed "flying disc". While the next day a higher command in the Army issued another press release calling the debris that of a weather balloon, rumors continued to circulate that alien bodies had been recovered. The press releases fueled public interest in UFOs and aliens and conspiracy theories that has flourished to today.
What I know of aliens and UFOs I learned from Hollywood films (or television shows from my childhood, like My Favorite Martian). And some of those films have great soundtracks. My favorite is the 1982 film E.T., with wonderful music by John Williams. Another film with music by John Williams is Close Encounters of the Third Kind. And there's James Horner's score to the 1986 film Aliens.
Celebrate the anniversary of the Roswell incident with a soundtrack from a sci-fi film, or watch the film, and remember that there may be aliens among us -- or all those UFOs could just be weather balloons.