As we seek to get a deeper understanding of the known objects in the Solar System, under-utilized senses may become a critical asset. Take sound, for instance.
Sound can be an approach to model data. It can portray the motion of hot gas as it responds to lighting on Saturn. In one technique called sonification, information from space telescopes can be put to musical sounds.
But there’s nothing quite like the real deal. In 2021, NASA’s Perseverance rover began to capture sounds from Mars. In a way, hearing a dust devil roaming over the alien landscape, along with the whirring of the wind, the flight of the first working helicopter on another planet, and a laser boring into Martian rocks feels slightly familiar.
But, obviously, they aren’t quite the same as their sonic counterparts would sound on Earth. This is a point highlighted by a panel at the 184th Meeting of the Acoustical Society of America on Thursday, where researcher Timothy Leighton, a professor of ultrasonics at the University of Southampton, and colleagues used available data on four Solar System worlds — Earth, Mars, Venus, and Saturn’s moon Titan — to show how sound changes from world to world.
As part of the session “Acoustic Sensing in Planetary Environments”, Leighton describes a software he created that can distort the human voice and other sounds to the predictions of what they’d sound like on other planets, based largely on atmospheric pressure. The point of this exercise, he tells Inverse, is to inspire a sense of awe and urgency about the perplexities of sound across the Solar System.
Soon-to-fly missions like NASA’s Europa Clipper will launch with a hardy suite of science instruments. Though this potentially-habitable world has been studied several times, there’s always more to learn.
One project scientist from the Clipper mission, Don Blankenship, thinks that microphones would be a nifty tool to use down the line. The spacecraft, launching next year, is not a landing mission, and will have plenty on its plate as it performs challenging flybys amidst the most perilous radiation environment in the Solar System, found around Jupiter. But microphones could eventually be a fantastic tool.
If the team wanted to know what Europa sounded like, the microphone would have to be able to do “everything,” Blankenship tells Inverse.
“Ice has an amazing capacity to propagate sound over very long distances without much attenuation (energy decay), which means that the sound from local cracking in the near-surface could be deafening and that sound from very deep cracking (even very small ones) could be detectable at very great distances,” Blankenship says.
Ahead of Leighton’s software development, he transformed Earthly recordings into audio clips of what they’d sound like on Venus, Mars, and Saturn’s moon Titan.
Titan is the most distant object ever visited by NASA. In 2005, the European Huygens landed on the surface of the frigid world, and it recorded about three hours of observations during descent and after touchdown. “If [Huygens] had had its back to a babbling brook, a microphone might have perhaps heard that,” Leighton says.
The warped audios that Leighton created account for how the alien environments would change the physics encountered by the sound’s producer — in each case, reality is suspended and it’s assumed that the vocal cords and the musical instruments are indestructible where they are.
On Venus, for example, Leighton says that vocal cords would have to work against the planet’s thick atmosphere. This would bring the pitch down, and even a child’s voice sounds quite bass.
Leighton’s goal is twofold, he says. First, he’d like to inspire the imagination. After all, sound can elicit a very personal feeling connecting us deeply to our surroundings. Second, he’d like to showcase the value of knowing how to interpret sound recordings from other worlds to account for local distortions that would signal one reality if they were coming from Earth, but which arise from another set of conditions someplace else. Ultimately, sound is an interpretation.
Take for instance, being underwater. Leighton says that if a swimmer is under the water’s surface in a pool, and someone is speaking on land, most of the sound would bounce off the liquid surface. This is a similar phenomenon that scientists encountered with NASA’s InSight mission when they’d try to listen to quakes below Mars’ surface, and would notice seismic waves that bounced off the surface of the Red Planet’s liquid core.
But if the person splashes into the pool, the swimmer already below the water’s surface may not just hear it with their ears, but with their bodies, too, Leighton says.
Back to the babbling brook of methane and ethane that Leighton envisioned on Titan when Huygens probe landed. In addition to our visceral reactions to that alien sound, such an audio file would also carry a lot of useful information. Bubbles in a stream of water are created when the water encounters different-sized rocks, Leighton says, and when each bubble bursts, “it sings one note.”
Maybe someday we’ll put our ears to the Universe in new creative ways.
