Listening to Alien Worlds

For decades, our exploration of other worlds has been dominated by images. We picture distant planetary objects through panoramas, mosaics, and false-colour maps; an achievement that I cover in great detail in my second book here. However, there is another way to experience some of these worlds: by listening to them.

Although several planets and moons possess atmospheres dense enough to transmit sound, only a small number of space missions have carried microphones. The most successful example to date is the Perseverance rover, which has been operating on Mars since 2021. Perseverance carries two microphones: one integrated with the SuperCam instrument, and another that documented the dramatic entry, descent, and landing sequence. These instruments do far more than satisfy curiosity. The SuperCam microphone listens to laser-induced shockwaves as rocks are vaporised, providing clues about their hardness and composition. It also records Martian wind, allowing scientists to study turbulence and atmospheric dynamics in ways that visual data alone cannot capture. Recently, the rover even recorded the crackle from dozens of 'mini-lightnings' on the surface of the red planet, as studied in this paper and heard here.

This success, however, came after decades of near misses. In 1999, the Mars Polar Lander carried the first serious attempt at a “Mars microphone,” developed as part of a Russian lidar instrument and funded by The Planetary Society. Had it worked, it would have been the first time humans heard the Martian environment directly. Unfortunately, the lander was lost during the descent stage, and the microphone never returned data. Nearly a decade later, the Phoenix lander also carried a microphone, this time attached to its descent camera. Once again though, no sound was returned as the lander encountered electrical problems, and the microphone was never switched on.

The idea of listening to other planets is even older. In the early 1980s, the Soviet Venera 13 and 14 landers descended through the crushing atmosphere of Venus. Alongside cameras and drills, they carried microphones designed to capture the sounds of the Venusian surface. These landers survived only minutes after touchdown, yet they demonstrated a bold willingness to treat sound as legitimate scientific data rather than a gimmick. In Venus’s dense atmosphere, acoustic measurements could, in principle, reveal wind behaviour, surface interactions, and mechanical responses in ways impossible on thinner worlds. The sound from Venera 13 can be found here, and Venera 14 here.

Sound has also been “heard” in less direct ways. During its descent through the atmosphere of Titan in 2005, the Huygens probe recorded acoustic data derived from pressure fluctuations and instrument responses. While not a traditional microphone recording audible sound, these measurements were later converted into sound-like representations, called “sonification”,⁠ offering insights into Titan’s thick, hazy atmosphere and surface interactions. The sounds of Titan can be heard here. Back on Mars, the InSight lander did not have a dedicated microphone. Still, it recorded the first-ever sounds of Martian wind using its highly sensitive seismometer and air-pressure sensor. These instruments captured vibrations from 10-15 mph winds blowing over the solar panels, which were then converted into audible sound as heard here. When the Parker Solar Probe picked up natural radio signals emanating from Venus' ionosphere during a flyby of the planet, this data was then converted into sound that can be heard here. All these are a reminder that sound does not need ears; it needs sensors and interpretation.

The gradual use of microphones or sonification in planetary missions reflects a broader shift in exploration philosophy. As we move from brief flybys to long-term presence, the goal is no longer just to see other worlds, but to experience them as physical environments. Sound adds texture to our understanding: the whisper of wind, the crack of stressed materials, the subtle signatures of atmosphere and surface interacting.

Listening to other worlds will not answer the grand questions of life or habitability on its own. But like all good science, it adds another dimension. And in doing so, it brings distant planets just a little closer, transforming them from silent images into places that feel, unmistakably, real.

As always, onwards and upwards.