[meteorite-list] Rosetta's Singing Comet

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4374

Rosetta's Singing Comet
Jet Propulsion Laboratory
November 11, 2014

[Audio File]
Sound wave superimposed on an image of comet 67P/Churyumov-Gerasimenko 
A set of instruments on the European Space Agency's Rosetta spacecraft 
has picked up a mysterious "song" from Comet 67P/Churyumov-Gerasimenko. 
Image credit: ESA/NASA/JPL-Caltech

A set of instruments on the European Space Agency's Rosetta spacecraft 
has picked up a mysterious "song" from Comet 67P/Churyumov-Gerasimenko. 
On Wednesday, Nov. 12, Rosetta will attempt the first-ever soft landing 
on a comet when it dispatches its Philae lander to the surface of comet 
67P.

The sounds are thought to be oscillations in the magnetic field around 
the comet. They were picked up by the Rosetta Plasma Consortium -- a suite 
of five instruments on the spacecraft that is orbiting the comet.

The comet's song would not be audible to the human ear because it is being 
emitted at 40 to 50 millihertz, far below the range of human hearing, 
which typically picks up sound between 20 hertz and 20 kilohertz. To make 
the sounds audible to humans, Rosetta scientists have increased the frequencies 
by 10,000 times.

The Rosetta's Rosetta Plasma Consortium consists of five instruments on 
the Rosetta orbiter that provide a wide variety of complementary information 
about the plasma environment surrounding Comet 67P/C-G. Plasma is the 
fourth state of matter -- an electrically conductive gas that can carry 
magnetic fields and electrical currents.

The consortium instruments are designed to study a number of phenomena, 
including the interaction of 67P/C-G with the solar wind, a continuous 
stream of plasma emitted by the sun; changes of activity on the comet; 
the structure and dynamics of the comet's tenuous plasma atmosphere, known 
as the coma; and the physical properties of the comet's nucleus and surface.

The comet sounds were heard clearly by Rosetta's magnetometer experiment 
for the first time in August, when Rosetta drew to within 62 miles (100 
kilometers) of 67P/C-G. Scientists think the sounds must be produced by 
the comet's activity, perhaps as it releases neutral particles into space 
where they become electrically charged, or ionized. The precise physical 
mechanism behind the oscillations remains a mystery.

"This is exciting because it is completely new to us. We did not expect 
this and we are still working to understand the physics of what is happening," 
said Karl-Heinz Glassmeier, head of Space Physics and Space Sensorics 
at the Technical University of Braunschweig, Germany.

Rosetta is a European Space Agency mission with contributions from its 
member states and NASA. Rosetta's Philae lander is provided by a consortium 
led by the German Aerospace Center, Cologne; Max Planck Institute for 
Solar System Research, Gottingen; National Center of Space Studies of 
France (CNES), Paris; and the Italian Space Agency, Rome. NASA's Jet Propulsion 
Laboratory in Pasadena, California, a division of the California Institute 
of Technology, manages the U.S. participation in the Rosetta mission for 
NASA's Science Mission Directorate in Washington.

For more information on the U.S. instruments aboard Rosetta, visit:
http://rosetta.jpl.nasa.gov

More information about Rosetta is available at:
http://www.esa.int/rosetta

Media Contact
DC Agle
818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle at jpl.nasa.gov

Dwayne Brown
202-358-1726
NASA Headquarters, Washington
dwayne.c.brown at nasa.gov

Markus Bauer
011-31-71-565-6799
European Space Agency, Noordwijk, Netherlands
markus.bauer at esa.int

2014-393