April 13, 2024

NASA’s mission to an ice-covered moon will contain a message between water worlds

NASA’s Europa Clipper spacecraft, headed for Jupiter’s ice-covered moon Europa in October 2024, will carry a laser-engraved message that celebrates humanity’s connection to water. The message pays homage to previous NASA missions that conveyed similar messages.

As president of Messaging Extraterrestrial Intelligence, or METI, International, I helped design the message in Clipper with two fellow members of our board of directors: linguists Sheri Wells-Jensen and Laura Buszard-Welcher. METI International is a scientific organization dedicated to transmitting powerful radio messages to extraterrestrial life.

We collect audio recordings in 103 languages ​​and decide how to convert them into waveforms that show these sounds visually. NASA colleagues recorded these waveforms on the metal plate that protects the spacecraft’s sensitive electronics from Jupiter’s strong radiation.

I also developed another part of the message that visually represents the wavelengths of water constituents, because water is very important to the search for intelligent life in the universe.

NASA’s design for the Clipper message heading to Jupiter’s moon Europa.

Recording messages on spacecraft is not a new practice, and Clipper’s message fits into a decades-old tradition started by astronomer Carl Sagan.

In 1972 and 1973, two Pioneer spacecraft headed for Jupiter and Saturn carrying metal plaques engraved with scientific and pictorial messages. In 1977, two Voyager spacecraft went to Jupiter, Saturn, Uranus and Neptune carrying gold-plated copper phonograph records. These records contained math and chemistry tutorials, as well as music, photos and sounds of the Earth, and greetings in 55 languages.

water words

As water is essential for life on Earth, the search for its presence in other places has been fundamental to many NASA missions. Astronomers suspect that Europa, where Clipper is headed, has an ocean beneath its icy surface, making it an excellent candidate for searching for life in the outer solar system.

Part of Clipper’s message features the word water in 103 languages. We started with audio files collected online, but then we needed to analyze them and find an output that could be recorded onto a metal plate. I ended up going back to some of the techniques I used in some of my early psycholinguistic research, where I explored how emotions are encoded in speech.

The 103 spoken words we recorded represent a global snapshot of the diversity of Earth’s languages. The outside of the Clipper board displays the words as waveforms that track the varying intensity of the sound as each word is spoken.

The waveform of the Catalan word for water – ‘aigua’ – is engraved on the Clipper sign. It also appears on the NASA website.
NASA/JPL-Caltech

Every person we recorded saying the word “water” to the waveform had a connection to water. For example, the lawyer who contributed the Uzbek word for water – “suv” – organizes an annual music festival in Uzbekistan to raise awareness about the desertification of the Aral Sea.

The native speaker of the Catalan word for water – “aigua” – hunts for exoplanets, discovering potentially habitable planets orbiting other stars.

Wavy lines radiating outward from a central point.
The Europa Clipper spacecraft, to be launched at Jupiter’s water moon in October 2024, includes a tantalum metal plate laser-etched with the word water in 103 languages ​​from around the world. Each word is shown as a waveform.
NASA/JPL-Caltech

The Drake Equation

Clipper’s message also pays tribute to astronomer Frank Drake, the father of SETI – the Search for Extraterrestrial Intelligence – by presenting the Drake Equation, his namesake formula. Based on scientific data as well as some educated guesses, the Drake Equation estimates the number of extraterrestrial civilizations in the galaxy that are currently sending messages into the cosmos.

According to one widely cited estimate, there are one-tenth as many extraterrestrial civilizations as the average human lifespan in years. If civilizations survive for a million years, for example, there should be about 100,000 in the galaxy. If they only last a century on average, scientists would estimate there are about 10.

An equation in cursive writing.
The Drake Equation is inscribed on the top of the inward-facing side of the plaque containing the Clipper’s message. It is written in Frank Drake’s handwriting.
NASA/JPL-Caltech

Radio astronomers study the universe by examining the radiation emitted by chemical elements in space. They spend much of their time mapping the distribution of the most abundant chemical substance in the universe – hydrogen.

Hydrogen emits radiation at a certain frequency called the hydrogen line, which radio telescopes can detect. During Project Ozma, the first modern SETI experiment, Drake looked for artificial signals at the same frequency because he imagined that scientists from other worlds might recognize hydrogen as universally significant and transmit signals at that frequency.

The water hole

As our team developed our water word message, I realized that the message would only make sense if it was discovered by someone already familiar with the content on the sign. The Drake Equation would only make sense if someone already knew what each of the terms in the equation represents.

The Europa Clipper will collide with Jupiter or one of its other moons, with Ganymede or Callisto being the main candidates. But if for some reason the mission changes and it survives that fate, then humans in the distant future, with a radically different cultural background and different linguistic conventions, could recover it millennia from now as an ancient artifact.

To ensure we had at least part of the message that a distant future scientist could understand, I also projected a pictorial representation of the same frequency that Drake used for Project Ozma: the hydrogen line. We record this on the Clipper board, along with a frequency called the hydroxyl line.

When hydrogen (H+) and hydroxyl (OH-) combine, they form water. Scientists call the band of frequencies between these lines the “water hole”. The well represents the part of the radio spectrum where astronomers conducted the first SETI experiments.

The inside of the Clipper's metal plate includes radio wave diagrams.
The inner side of the Europa Clipper message includes wavelengths from the hydrogen and hydroxyl emission lines. These represent the components of water. The band of frequencies between these lines is called the ‘water well’.
NASA/JPL-Caltech

We display the hydrogen and hydroxyl lines using their wavelengths in the Clipper message. The metal plate also has diagrams showing what hydrogen and hydroxyl look like at the atomic level.

We hope that future chemists will recognize these chemical components as ingredients in water. If they do, we will have managed to communicate at least some fundamental scientific concepts across time, space and language.

Waveforms allow our team to stitch messages together on both sides of the Clipper board. On the water words side, more than a hundred words are represented by their waveforms. On the other hand, the wavelengths of hydrogen and hydroxyl – the constituents of water – are engraved on the plate.

METI International funded the collection and curation of the water words, as well as my hydrogen and hydroxyl lines project, providing them free of charge to NASA.

When designing the message for the Europa Clipper, we had to reflect on the importance of water on Earth and think about why astronomers feel so compelled to look for it beneath the icy crust of Jupiter’s moon Europa. The spacecraft is scheduled to enter Jupiter’s orbit in April 2030.

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