The Slow Sound of a Scream on Mars

In space, no one can hear you scream, the saying goes. But what about on the surface of Mars?

A new computer simulation reveals just how far sound waves travel on the red planet. And if you're screaming for help, you better hope people are nearby.

Sound in air, water or any medium travels in waves that propagate as one molecule collides into the next, and so on. Because the Martian atmosphere is much thinner than Earth's, the distance between molecules is 120 times as far as in your back yard.

Scientists from Penn State University set up a computer simulation to figure out how far a sound wave would travel in Mars' thin air.

On Earth, the sound from an average scream might travel about three-quarters of a mile, depending on conditions. But it would only make it about 53 feet on Mars, according to Amanda Hanford, a researcher on the project.

Similarly, sound produced by a lawnmower travels several miles in open air on Earth, but would go only a couple hundred feet on Mars.

Sound on Mars also travels more slowly, and Hanford said that means you might not recognize your own voice.

"If you were able to produce vocal sounds on Mars-that is, if you were able to breathe carbon dioxide-your voice would be lower," Hanford told

It's the reverse of talking like a chipmunk after inhaling helium. Helium gas has a higher speed of sound than the air we normally breathe, which causes our voices to sound a few octaves higher.

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