Sounding Off on Mars

The Martian atmosphere is 0.7% as dense as Earth's, so one would expect sound (pressurized waves of moving air molecules) to fade in intensity quickly on Mars. Unfortunately, the 1999 Mars Polar Lander, which was equipped to record sounds directly in the Martian atmosphere, was lost before it could conduct the tests.

Fortunately, in yet another report from last week's Acoustical Society of America meeting, researchers have run a molecule-by-molecule computer simulation of how sound would travel in the Martian atmosphere. The results of this analysis show that sounds die off rather quickly - the absorption is 100 times greater than on Earth, in fact. On Earth a sound in the ultrasonic spectrum might extend for kilometers, but on Mars it will die off within a few tens of meters. (Due to the nature of the experiment, it was conducted with low-wavelength, ultrasonic simulations and extrapolated to the audible sound range.)

Though this die-off was expected, having a means to actually analyze the sound will be crucial for any future Mars missions. Explorers on Mars will need to understand what they can expect in that terrain. To communicate audibly, for example, there may need to be some sort of device to transmit sound in lower frequencies, which would be more clearly transmitted on Mars.

Related articles:
• AIP News: "Your Neighbors Would Love You on Mars"
• Science: "On Mars, No One Can Hear You Scream"

Other reports from the Acoustical Society of America meeting:
• Lay Language Papers from the 151st ASA meeting
• Ultrasound Laser ("uaswer") Built
• Nanowires Get Plucked

Special thanks to Ben Stein, of the American Institute of Physics, for making me aware of this report. (No, before you ask, I don't think it's that Ben Stein.)