The original Arecibo message was designed by Dr. Frank Drake, with the help of Dr. Carl Sagan and the Arecibo Observatory (AO) staff (previously named NAIC - National Astronomy and Ionosphere Center), and was sent out on Nov 16th, 1974, characterizing the most powerful (3x1012 W) broadcast ever beamed into the deep space at the time.
In the 1974 transmission, a set of one-s and zero-s were combined into the famous 1679-bit picture representing a message from Earth to our possible extraterrestrial neighbors, telling them our address in the Solar System and a little bit of our nature.
The Arecibo message was sent in the direction of the globular star cluster M13, in the Hercules constellation, hoping to be heard by any kind of intelligent civilization living in the edge of the Milky Way.
At that time, there was no knowledge about Exoplanetary systems (the first Exoplanet was discovered at Arecibo Observatory in 1992) and no debate about the possible risks of interestellar messaging. Moreover, today we are able to use our communication on social medias as an example of the impacts of sharing personal information without filtering the recipients.
Numbers from 1 to 10 (white pixels): this shows how numbers are represented throughout the rest of the message. In all places where a number is shown, the pixels are colored white
Atoms (purple pixels): the atomic numbers (the number of protons, which uniquely identify each kind of atom) of hydrogen, carbon, nitrogen, oxygen, and phosphorus. These are the basic atoms needed for the biochemical description of life
Sugars and bases (green pixels): the chemical formulae, using the atoms described above, that are the sugars and bases that make up the nucleotides, the building blocks of DNA.
Double Helix (blue pixels): the DNA double helix; the number it winds around is the number of nucleotides in a strand of human DNA
Human Figure (red pixels): the DNA terminates on the organism it represents, the human figure. On the left is a bar and number representing the average height of a human (in wavelength = 1110x12.6=1.764m), and on the right is the total population of humans on Earth (4.29 bi in 1974)
Solar System Map (yellow pixels): a map of the solar system from where the message came; the third planet is offset toward the figure, indicating this is the organism that sent the message
Arecibo Telescope (purple pixels): a graphic of the telescope that sent the message, with a line and number underneath it telling how large it is: in wavelengths = 2430 x 12.6 ~ 300m.
On November 16, 1974, the Arecibo Observatory transmitted at 2380 MHz at an effective bandwidth of 10 Hz a message directed at the globular cluster M13. The message consists of a 1679-bit picture portraying a counting scheme, five biologically significant atoms (H, C, O, N, and P), the genetic structure of the four purines and pyrimidine bases of DNA; a schematic of the DNA double helix with an order-of-magnitude estimate of the number of base pairs; a representation of a human being and his or her dimensions; a depiction of the solar system with an indication that human beings inhabit the third planet and an estimate of the human population of the Earth; and finally, a schematic representation of the Arecibo Observatory and a description of its dimensions. - Received 16 June 1975, Available online 26 October 2002 through Cornell University Library.