Lots of red dust, but not much noise

In space, no one can hear you scream. A new analysis suggests that it’s pretty quiet on Mars, too.

When NASA lost the Mars Polar Lander as it arrived at the Red Planet in December 1999, scientists lost their first chance to hear the sounds of another planet—there was a microphone on board that craft.

To simulate how sounds are transmitted on Mars, acoustics researchers Amanda D. Hanford and Lyle N. Long of Pennsylvania State University in University Park used a computer model that considered the density, temperature, and composition of the Martian atmosphere.

For instance, the average atmospheric pressure on the surface of Mars is only about 0.7 percent of that found on Earth at sea level, says Hanford. In that environment, molecules travel about 6 micrometers between collisions with each other, or roughly 120 times farther than they do in Earth’s atmosphere. Therefore, sound isn’t transmitted as effectively on Mars as it is here.

The researchers’ simulations suggest that the sound of a loud scream—which on Earth can be heard as much as 1,000 meters from its source—would travel only 16 m on Mars.

Besides merely satisfying curiosity, results of this study have many implications, including how loudspeakers used during Martian exploration should be designed and how much electrical power would be needed to create sounds that could be heard over long distances, says Hanford. She and Long reported their results at the Acoustical Society of America meeting in Providence, R.I., on June 6.