As Cosmos: A Spacetime Odyssey reminded us during its final episode, “No other objects touched by human hands have ever ventured this far from home.” Indeed, the two Voyager spacecraft are sailing ever farther from home, exploring the solar system’s frontier like the maritime surveyors of yesteryear.

Except these explorers are never coming back.

For the next decade or so, the spacecraft will continue to send messages full of data to their home planet. But then, eventually, their power supplies will dwindle and those messages will fade. As the silent spacecraft sail through an even quieter cosmic sea, their primary mission will no longer be to gather data. It will be to ferry the murmurs of Earth, inscribed onto those