Can you hear me now? Not on Mars:

She said a sound's lower pitch is the result of the differences in the speed of sound. This is because of the Red Planet's atmospheric makeup -- mostly carbon dioxide, with small percentages of nitrogen and argon with trace amounts of water vapor and oxygen.

"When you breathe in a helium balloon and speak, your voice is a high pitch," Hanford explained. "Assuming you could breathe in carbon dioxide (which is very toxic), your voice would be a lower pitch."

Someday, someone is going to actually experience this for themselves, and no doubt remark in a deep yet faint voice, "By golly, their simulations were right!"...before promptly dropping dead from asphyxiation.

The distance sound can travel is also greatly affected by the Martian atmosphere.

"The lower pressure makes it so sound doesn't travel far," she said. According to the paper, sound generated by a human scream on Earth can travel a little over a kilometer before being absorbed by the atmosphere. On Mars, the sound from that same scream would only move about 16 yards at best.

Even if propagation is weak, I would expect surface suits to have an external audio pickup. Holding a conversation through the air would have little utility given the availability of radio links, but surface ambient sound would still be useful for nonverbal purposes -- for instance, the auditory cues one uses to determine whether a power tool is functioning properly or is being over-worked, or a warning that a rover (or a fellow astronaut with cabin fever and a claw hammer) is approaching from behind. Beyond the functional utility, there may also be psychological benefits from being able to hear the surface, offsetting the sense of isolation or alienation from the Martian environment that comes from only ever experiencing it through protective gear.

Posted by T.L. James on July 3, 2006 08:27 PM | TrackBack