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What does a
waterfall sound like in space?
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Photo: Steve Shrimpton
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The
answer to this fascinating question may be found on
Titan, Saturn's largest moon. Professor Tim Leighton of
the University's Institute of Sound and Vibration
Research (ISVR) has speculated how the sound of
splashing liquid in deep space might differ to that
heard on Earth. It is possible that his theory could be
proved later this year by NASA's Cassini mission to
Saturn. In the meantime, he has recreated the sound he
believes it makes and put it on the
Internet.
NASA's Cassini space craft went
into orbit around Saturn on 1 July. It will study the
planet, its moons and rings for four years. However, in
Professor Leighton's view, possibly the most interesting
aspect of the Cassini Mission, is the European Space
Agency's probe Huygens, which will study Titan. After a
seven-year journey strapped to the side of Cassini, the
probe will separate from it on Christmas Day 2004 and
coast for 20 days before parachuting through the thick
atmosphere to become the first man-made object to land
on the moon of another planet on 14 January
2005.
Titan's thick smog has prevented previous
spacecraft photographing its surface, but there are
suggestions that the moon may be home to seas and
streams made, not of water, but of liquid ethane. The
main focus of Huygens' mission is to sample the
smog-laden atmosphere, but three minutes of battery time
will be used for investigations immediately after
landing. Although the probe's microphone is on board
primarily to monitor atmospheric buffering, Professor
Leighton has suggested that, were the microphone to
detect a splash-down as opposed to a crunch on landing,
the question of what a splash in space might sound like
would be answered.
Professor Leighton, who has
speculated for several years on sounds in space,
explains: 'I began asking if the noise of splashes,
which is so familiar to us on Earth, would be
recognisable in a sea of liquid ethane at a temperature
of 180 degrees below zero. NASA's specially-commissioned
painting of a waterfall-actually a methane fall-on Titan
inspired me to attempt to predict how it would
sound.
I set up the equations and measured the
sound of a small waterfall in nearby Romsey. My
colleague Dr Paul White then processed the signal to
obtain what we believe would be the sound of a methane
fall on Titan.
'Given that the last decade has
seen an explosion in the amount we can learn about the
oceans simply by listening to them, from storms to
seabed properties to coastal erosion, acoustics
represent a potentially exciting and comparatively
low-cost method of space exploration.'
Professor
Leighton outlines his ideas for the role of acoustics in
space exploration in an article entitled 'The Sound of
Titan' to be published in the July/August edition of
Acoustics Bulletin. The sound of the methane fall as
calculated by Professor Leighton and Dr Paul White can
be heard online at www.isvr.soton.ac.uk/fdag/uaua
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