Listen Up! Microphones to Fly to Mars

What does Mars sound like?  We’ll get another chance to find out. The Mars 2020 mission has announced that microphones will fly on board their rover, a near-copy of Curiosity but with different instruments. There will be JPL-provided Entry, Descent, and Landing (EDL) microphones, and there will be a microphone included in the SuperCam science instrument, led by Roger Wiens at Los Alamos National Laboratory in partnership with the French Space Agency, CNES. This is very exciting news for The Planetary Society and its members, who have been trying to get microphones to Mars for the last 20 years, including flying the first-ever Mars Microphone on the failed Mars Polar Lander mission. The Planetary Society and its members, and their efforts, were crucial in continually putting the idea of microphones forward into the consciousness of Mars exploration. Congratulations, microphones will fly again!

Microphones will finally enable us to add a second human sense to all the amazing visual imagery we have seen from Mars, adding a visceral reality to a distant world. Sounds from Mars have been something the public has long found fascinating and, as a result, that The Planetary Society has embraced and pursued.

"One test is worth a thousand expert opinions," said Bill Nye, CEO of The Planetary Society, in response to the news. "At last we will hear the sounds of Mars. Stay tuned, and get ready to turn this mission up loud!"

A Brief History of No Martian Sounds

Co-founder of The Planetary Society Carl Sagan was perhaps the first to formally suggest the idea of placing a microphone on Mars. Sagan wrote in a 1996 letter to NASA, "Even if only a few minutes of Martian sounds are recorded from this first experiment, the public interest will be high and the opportunity for scientific exploration real."

The Planetary Society flew the Mars Microphone on NASA’s Mars Polar Lander mission in 1998 as part of a Russian LIDAR instrument. It was not only the first microphone to go to Mars, but also was the first privately funded planetary experiment. Sadly, Mars Polar Lander crashed on Mars in 1999, but The Planetary Society didn't give up.

The Planetary Society Mars Microphone was selected to fly on the ultimately cancelled CNES Mars Netlander missions. The Society, including the creator of the Mars Microphone, Dr. Greg Delory of UC Berkeley, worked with the acoustic sensor on Cassini-Huygens to turn science data into sound for the public from Titan in 2005, "hearing" the wind sound of descent through the atmosphere. In 2007, The Planetary Society partnered with Malin Space Science Systems on their microphone in the Phoenix descent imager. This second microphone to fly to Mars, on Phoenix, was never turned on because of the potential for an electronic problem.

Mars remained silent. Well, really, it was really more of a question of if a dust devil moves over your spacecraft on Mars, but no microphone is there to hear it…well, you get the idea. The Planetary Society alone or with partners tried to get microphones on every lander that has gone to Mars since Mars Polar Lander. Some were detailed proposals and technical studies; some were quick rejections. None were scrapped due to technical flaws. So why has it been so hard to fly microphones to Mars?

The gist of the challenge has been convincing space agencies that microphones are worth the resources in terms of time, mass, data, and added complexity. Microphones have trouble competing with other instruments on a science or engineering basis alone, which is often the determining factor for what flies and what doesn’t. Microphones have come close to flying again before now, but in the end, each mission team has not wanted one more thing to think about among the rest of their engineering challenges. I go into more detail about this in a Q and A piece just came out in Astronomy magazine on why microphones are hard to get on Mars missions. 

What is Flying on Mars 2020?

The SuperCam microphone ties specifically into their science. SuperCam, the follow-on to ChemCam on Curiosity, uses Laser Induced Breakdown Spectroscopy (LIBS)—vaporizing rock with a laser and analyzing the spectral result to determine composition of the rock. Its microphone can enhance their science, since testing on Earth indicates that analysis of the volume of the sound (kind of a crack or loud pop) can be used to study the mass of material vaporized by a laser shot. You can find more details in our previous blog post about this microphone having been proposed.

It also should be able to detect other sounds of science, engineering, and public interest, from blowing winds to the crunch of the wheels rolling across the surface. The Planetary Society has been working with the SuperCam team and discussing possible ways to collaborate with their microphone. We’ll be bringing you more details on the SuperCam microphone in the future.

The EDL microphones, which will have an engineering angle in addition to public interest, were mentioned in the NASA press release and Facebook Live Update, including "There will be a suite of cameras and a microphone that will capture the never-before-seen or heard imagery and sounds of the entry, descent and landing sequence. Information from the descent cameras and microphone will provide valuable data to assist in planning future Mars landings, and make for thrilling video."  Thrilling indeed.

Mars 2020 Deputy Project Manager Matt Wallace of JPL said, "This will be a great opportunity for the public to hear the sounds of Mars for the first time, and it could also provide useful engineering information."

Quick Tutorial on Martian Sound

Mars’ atmosphere is much thinner than Earth’s, mostly carbon dioxide, and colder than Earth’s. Since sound utilizes the medium it is in, in this case the Mars’ atmosphere, things change on Mars. One big effect is sound attenuation: a given sound will not travel as far as it would on Earth. The Planetary Society, SuperCam, and others have studied this and found that we still should have plenty of volume for nearby sounds for the sensors.

Another interesting thing to ponder is that if one spoke in the Mars atmosphere (suspend your disbelief for the sake of science for a moment), your voice would come out lower in frequency. This is basically the opposite effect of speaking after breathing in Helium. Below is a Random Space Fact video where my voice is simulated as it would sound on Mars. And, here you can learn more about Mars sounds and hear several people with simulated Mars voices including Ray Bradbury, Bill Nye, and James Cameron. In general, you can find more about Mars Microphones in our planetary sounds section.

Hear It!

The Planetary Society is ecstatic with the news of microphones heading back to Mars. I personally have been working on getting more Mars Microphones for almost 15 years, and The Planetary Society has been pushing for two decades. Carl Sagan himself began the push. And, if you are one of The Planetary Society members or supporters who have helped us in this endeavor, I hope you are not only ecstatic but feel proud as well. We made some noise, while hoping to one day be able to listen to Martian noise. We raised awareness of the very concept of a planetary microphone as something that would be of enormous public interest as well as of potential science and engineering benefit. We seeded the process by building and flying the first Mars Microphone. And now, some extremely capable organizations have picked up the ball and microphones are headed to Mars once again. We’re listening!