An alternative scenario: aliens pick up our first broadcast message capable of travelling through outer space - featuring one A. Hitler at the 1936 Olympics - and decide they should investigate.

They arrive to find nothing but a scorched planet, and a hologram of Charlton Heston repeating on loop 'You maniacs! You blew it up! Damn you all to hell!'.

'Nothing to see here,' they shrug. And head off in search of intelligent life elsewhere...