Messages are to be beamed to a planet 20 light years from Earth in the hope they will reach intelligent alien life, BBC reported.
Some 501 photos, drawings and text messages are being transmitted by a giant radio-telescope in Ukraine normally used to track asteroids.
The target planet was chosen as it is thought capable of supporting life.
Any reply to the messages - collated through a competition by the social networking website Bebo - would not reach Earth for 40 years.
The competition - A Message From Earth - invited Bebo`s 12m users to send in missives they would like extra-terrestrials to receive.
Topics submitted ranged from the environment, politics and world peace to family relationships and the sender`s first kiss.
Having been translated into a binary format, the 500 selected will be sent 120 trillion miles into space via high-powered radio waves from the National Space Agency of Ukraine`s RT-70 radar telescope in Evpatoria.
Here we are
The beamed communication will be transmitted at 0600 GMT, passing the moon in just 1.7 seconds and taking less than seven hours to leave our solar system.
Organisers hope the hi-tech package will reach its target - the planet Gliese 581C - in early 2029.
Bebo spokesman Mark Charkin said: "A Message From Earth presents an opportunity for the digital natives of today... to reconnect with science and the wider universe in a simple, fun and immersive way."
Seth Shostak, a senior astronomer from the Search for Extra Terrestrial Intelligence Institute in California, said whether aliens who might receive the messages would understand them was beside the point.
"The point might simply be: well, here we are; we`re clever enough to build a radio transmitter," he told the BBC.
"So if anybody`s out there and they find that signal, they at least know it that, in the direction of that star system over there, there must be a planet with some pretty clever things on it."