Date: August 20, 2010

Title: Music on a Planetary Scale


Podcaster: Sandy Antunes


Description: Listen to Mars, now listen to me, now listen to Mars. This is what Mars could sound like, if it sounded like me. Today, we listen to sonification of data, artistic interpretation, and discuss which is ‘better’ and which is ‘more real’. Can we hear a point to converting astronomy data to sound? I’m on a podcast.

Bio: Sandy looks at the science and the people in today’s 9-5 pro astronomy world. Born in the heart of a dying star (as we were all), Alex draws from his research, writing, and game design work to bring you the joy of science twice a week at– and to launch the first personal science/music satellite via

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the Physics Department at Eastern Illinois University: “Caring faculty guiding students through teaching and research” at


(all spoken by Sandy):

Today’s question: What’s the difference between an astrologer and an astronomer?

The answer is: Astrologers get paid more. Rim shot there. Thank you very much. Tip your waitress.

Also, astrologists get to just make stuff up. That is a luxury we don’t have in astronomy, unfortunately. So from this we’re going to segue awkwardly to the classical music piece, Holst the Planets.

As a music piece, it’s brilliant! Let’s listen to the first planet, and I’m really going somewhere with this, “Mars: Bringer of War”

[CLIP 1, Percy Grainger directs]

That’s Great stuff. It Sounds like movie themes, and I don’t mean that as an insult. It’s just very sweeping, evocative, you get visual imagery. Now, here’s what Mars actually sounds like, as captured by the Phoenix lander and relayed through the Mars Express orbiter. Go ESA!

[CLIP 2, EDL_signal_received_by_MELACOM_versus_time_converted_in_Audio_v3.mp3]

That was the Phoenix lander actually landing, so you have Mars– windy, cold, thin air. It’s not as majestic in audio as the classical music piece, but it is way more real.

Now, Holst self-admitted he based his work on astrology, not astronomy, so I have no expectation of physical accuracy for his composition. And I can forgive him putting the planet order starting with Mars, jumping to Venus, then popping out to Jupiter. That’s dramatic license

I can even forgive him for neglecting Pluto as a planet. A later composer added a ‘Pluto’ composition to the mix, and, after Pluto got down-voted to ‘not-planet’, they even pulled the Pluto piece. Poor Pluto, even in the music business it can’t get a break.

Anyway, let’s hear Holst’s take on Jupiter:

[CLIP 3, Percy Grainger directs]

And here is a sonification of Jupiter radio emissions. Real data to compare with the artistic license. This is a transcript of “Voyager 2 Passing Through Jupiter’s Outer Magnetosphere”.

[CLIP 4, jovefuh-dag.wav]

Now the formal definition of these sonification from the NASA site is “These melodious tones are created at a special frequency in a plasma with a magnetic field. The frequency is set by the number of electrons in a given volume (the electron density) and the strength of the magnetic field. Hence, the frequency of these waves, called upper hybrid waves, can provide a very accurate measure of the density of the plasma; a fundamental property of the Jovian environment of interest to scientists. These emissions were acquired by Voyager 2 as it passed through the outer magnetosphere in 1979.”

Now, what do these all have in common, the classical music and the sonifications? Very little, actually. The Holst bits are just concepts, they’re fictional stories that happen to share their names with various planets. The actual sound, the actual data, what little we’ve captured, are basic reality, whether we like it or not.

And that weird middle ground, sonification of data, is an odd critter. Sonification means taking data from one non-sound realm (such as radio emission from Jupiter) and shifting it to audio so we can try to pick out patterns with our ears. Our ears and brain are a really good pattern-matcher– so much so that we sometimes perceive patterns where they don’t exist.

I like sonification of data. It’s like adding false color to X-ray images of stars, or mapping out radio data into contours to better show how the radio emission actually stack up or change in a picture.

Now, from, they have this great explanation of sonifying radio data, “The power of a radio signal is analogous to the volume of a sound. The radio signal also varies in terms of the frequency and wavelength of the radio waves, which is like the variation in pitch of sound waves. So scientists sometimes translate radio signals into sound to better understand [those] signals.”

Back to my take on it. Sonification is very accurate, in that it takes the real data and translates it with fidelity to another realm– that of sound. Yet it’s also an artistic effort of sorts, a translation that intends to reveal more at the risk of drifting from the original raw source.

I’m working on a sonification project myself, a satellite called Project Calliope, that will convert the Earth’s ionosphere to real-time sound. And what will that sound like?

The answer is, it will sound like the ionosphere, mapped to mimic any sound that you wish. Which is as close to a non-answer as I dare risk. So let me cover that in a future podcast. For now, this is Dr. Sandy Antunes, the Daytime astronomer, signing off.

You can read my work twice a week at (the new name for, focusing on exploring the new field Science 2.0). Until next month, happy listening!

End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the Astrosphere New Media Association. Audio post-production by Preston Gibson. Bandwidth donated by and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at or email us at Until tomorrow…goodbye.