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Wednesday, November 12, 2014

Rosetta's comet sings a mysterious 'song'

© ESA/Rosetta/NavCam
Through some kind of interaction in the comet's
environment, 67P's weak magnetic field
seems to be oscillating at low frequencies.
SOTT | Nov 12, 2014 | Ian O'Neill

The Rosetta mission has detected a mysterious signal coming from Comet 67P/Churyumov-Gerasimenko.

The mission has five instruments in the Rosetta Plasma Consortium (RPC) that measure the plasma environment surrounding the comet.

Plasma is a charged gas and the RPC is tasked with understanding variations in the comet's activity, how 67P's jets of vapour and dust interacts with the solar wind and the dynamic structure of the comet's nucleus and coma.

But when recording signals in the 40-50 millihertz frequency range, the RPC scientists stumbled on a surprise - the comet was singing, they report.

Through some kind of interaction in the comet's environment, 67P's weak magnetic field seems to be oscillating at low frequencies. In an effort to better understand this unique 'song', mission scientists have increased the frequency 10,000 times to make it audible to the human ear.

First detected in August as Rosetta approached the comet from 100 kilometres, this magnetic oscillation has continued.

Rosetta scientists speculate that the oscillations may be driven by the ionisation of neutral particles from the comet's jets.

As they are released into space, they collide with high-energy particles from interplanetary space and become ionised. Because it is electrically charged, the plasma then interacts with the cometary magnetic field, causing oscillations. But to draw any conclusions about this, further work is needed.



"This is exciting because it is completely new to us," says Karl-Heinz Glaßmeier, head of Space Physics and Space Sensorics at the Technische Universität Braunschweig, Germany.

"We did not expect this and we are still working to understand the physics of what is happening."

Rosetta is currently lining up to deploy its robotic Philae lander to the comet at 20.00 AEDT.

During landing manoeuvers, the RPC is expected to help tracking Philae's descent to the comet's surface. The time between separation and landing is expected to take around seven hours.

It takes 28 minutes and 20 seconds for signals to travel at the speed of light from Rosetta to mission control in Germany.

ABC Science, Australia

Source: Discovery News

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