Water and the Drake Equation: NASA will send a message to Europa

Following its long-standing tradition, NASA will install a metal plate on board the Europa Clipper. A symbolic message will be engraved on it.

Connected by water

The Europa Clipper mission will be launched in 2024. The purpose of the spacecraft is Europa— a moon of Jupiter, under the icy surface of which a huge ocean hides. According to some researchers, the conditions inside it may contribute to the emergence of life. Therefore, the mission developers decided to install a kind of message on the spacecraft — from one oceanic world to another.

The message is engraved on a metal plate. It is part of the structure that protects Europa Clipper electronics from radiation. The plate is made of tantalum, its dimensions are 18 cm by 18 cm, thickness is 1 mm. It is covered with graphic elements on both sides. 

The front side of the message plate mounted on the Europa Clipper. Source: NASA/JPL-Caltech

The outer side of the plate is dedicated to water. It connects all living things and all human cultures. The authors of the message have collected audio recordings of the word “water”, pronounced in 103 languages of the world (including Ukrainian). Then they were transformed into waveforms (a visual representation of sound waves) and engraved on the plate. The words diverge from the circular symbol representing the “water” sign in American sign language. It was created using a data processing and compression technique called Fourier transform.

Message in a bottle

The reverse side of the plate contains several blocks of information at once. Its main part is occupied by an engraved handwritten text of the poem, specially written for the mission by the poet laureate of the USA Ada Lemon. 

The reverse side of the message plate installed on the Europa Clipper. Source: NASA/JPL-Caltech

Along with the poem, the names of 2.6 million people that have participated in NASA’s “Message in a Bottle” initiative will also go to Europa. They are engraved on a silicon chip the size of a fingernail. It will be installed in the center of a drawing depicting the orbits of Jupiter’s four largest moons. In the center of the drawing is a bottle symbolizing the NASA initiative.

Life in the Universe

One of the main sources of inspiration for the Europa Clipper message, as well as other similar letters to space, is the idea of the habitability of other worlds. Unsurprisingly, the famous Drake equation was engraved on the plate. This is a mathematical formula describing the probability of detecting a developed and able to maintain contact civilization in the Milky Way. Despite the controversy over its scientific validity, the Drake equation has become an important source of inspiration for a number of studies related to astrobiology. Therefore, the authors of the message decided to pay tribute to it.

Drake equation, engraved on a plaque mounted on board the Europa Clipper. Source: NASA/JPL-Caltech

The message also contains an engraved schematic image of the so-called “water hole”. This is what astronomy calls the range between the hydrogen emission line at a frequency of 1420 megahertz and the hydroxyl line at a frequency of 1660-1666 megahertz. They are relatively free from background noise and are therefore considered by some researchers to be ideal for interstellar communication. These lines are also a scientific and mathematical way of expressing the word “water” — because the chemical symbols of hydrogen and hydroxyl, H and OH, represent the products of splitting water molecules (H₂O).

And finally, the message also featured a portrait of Ron Greeley (1939-2011), considered one of the founders of planetary science. He participated in a number of space missions and was a mentor to many researchers, including those who are now members of the Europa Clipper scientific group.

According to https://europa.nasa.gov

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