The following is an excerpt from Daniel Lametti | August 29, 2012 | Slate.com |
Yesterday, NASA’s Curiosity rover broadcast a song by singer-songwriter will.i.am from Mars. The rover, you might have heard, is currently roving the surface of the planet, and the new track sent back to Earth was titled “Reach for the Stars.” Although it’s tempting to criticize NASA for using a $2.6 billion dollar scientific instrument to transmit pop music, the event was marketed as educational. “Members of the team that successfully landed the rover on Mars earlier this month,” NASA wrote in a press release, “will explain to students the mission and the technology behind the song’s interplanetary transmission.” That’s interesting. But what would the tune sound like if it were played on Mars? Would it have that same “Boom Boom Pow”?
Not quite. If “Reach for the Stars” was recorded on Earth and then played from a rover-mounted speaker, the main thing we’d notice is that, ten meters from the sound source, the song would be imperceptible. Sound is perceived when our ears detect the vibrations of molecules in the atmosphere. Earth’s atmosphere consists mostly of nitrogen and oxygen; Mars’s atmosphere is, for the most part, made up of a very thin layer of carbon dioxide. The molecular structure of carbon dioxide makes it a great sound absorber, and, more generally, sound propagates poorly in a thin atmosphere. As Timothy Leighton, a professor of ultrasonics and underwater acoustics at the University of Southampton, told me, “Mars is quite dead acoustically. You’d have to be pretty close to the sound source to actually hear anything.”
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