March 2021 Newsletter: Mars Bars

With the world watching, Perseverance successfully touched down on Mars on February 18, 2021. This car-sized rover is there to identify signs of ancient life, collect soil and rock samples, and test oxygen production to prepare for future crewed missions. In addition to a cadre of scientific instrumentation, the rover is equipped with two microphones, which allow us to listen to sounds on Mars for the first time. Read on to learn more about Martian murmurs.

One of the microphones is part of the SuperCam instrument on top of the rover’s mast.  SuperCam fires a laser at distant rock targets to help determine their composition.  Based on the results of that laser pop, scientists may get more information about the rock hardness, mass, and type.  Listen here for the first recording of the laser’s firing. 

 SuperCam with microphone location circled in blue.

The second mic is an off-the-shelf commercial product attached to the side of the rover.  Interestingly, the microphone was not expected to survive the descent, but it did and is now recording the sounds of Mars!   NASA’s website has samples of the audio that has been recorded thus far on the surface of Mars.

 Microphone location circled in blue.

You may be wondering what everyday noises on Earth sound like on Mars, which has an unusual atmosphere compared to Earth with very different temperature, density, and chemistry.  The average surface temperature on Mars is -80°F, which reduces the speed of sound propagation – around 540 mph compared to about 760 mph on Earth. You probably wouldn’t notice close to a sound source, but over longer distances you would notice a larger delay between an event and the sound associated with it, like when you see a batter hit a home run at Citizen’s Bank Park from the nosebleed section and hear the thunk of the hit a moment later.  

Because the Martian atmosphere is about 100 times less dense than on Earth, sounds are attenuated much more by the atmosphere as they propagate through it.  You’d have to be much closer to the source of a sound to hear it on Mars at the same level as you would on Earth.  The third difference is the sound quality; the atmosphere of Mars, made up of 96% carbon dioxide, would absorb much more high-frequency sound energy, so only lower-pitched sounds would travel long distances: an apt comparison is the sharp crack of thunder from a nearby strike to the low rumble from a distant strike.  This link has a comparison of everyday sounds on Earth compared to how they would sound on Mars.

 Mars surface from Rover.

It will be quite a while before humans can hear themselves on Mars, but as for sounds on Earth, we have missed many this past year during COVID. Some favorites that come to mind include live music, crowds cheering at a sporting event, laughing with friends and family, and the happy sounds of children playing nearby.  We look forward to hearing those and more very soon!

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