[meteorite-list] Cassini Discovers Music of the Rings

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Nov 9 20:34:49 2004
Message-ID: <200411100134.RAA10709_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99996639

Cassini discovers music of the rings
David L. Chandler
New Scientist
November 9, 2004

Saturn's magnificent ring system - a huge disc resembling an old
gramophone record - turns out to share another property with the LP: it
constantly emits a melodic series of musical notes.

The surprising discovery was made by radio and plasma wave detectors on
board the Cassini spacecraft as it passed over Saturn's rings during its
arrival at the planet in July.

The tones are emitted as radio waves. Don Gurnett of the University of
Iowa says his team reduced their frequencies by a factor of five to
bring them into the range of human hearing. Gurnett says he was
"completely astonished" when he heard the musical notes.

The tones are short, typically lasting between one and three seconds,
and unlike the ethereal sliding tones associated with other cosmic
processes, every one is quite distinct. The evidence suggests that each
tone is produced by the impact of a meteoroid on the icy chunks that
make up the rings.

Each hit, Gurnett says, creates a pulse of energy that is focused along
the surface of a cone from the point of impact. By estimating the energy
involved, he calculates that the impacting objects are about 1
centimetre across - although he cautions that his estimate could be out
by as much as a factor of 10.

The findings were reported on Monday at the annual meeting of the
American Astronomical Society's Division of Planetary Sciences.

Noisy collisions

Planetary scientists have assumed that meteoroids constantly collide
with Saturn's rings, says Cassini imaging team leader Carolyn Porco, and
that process has been suggested as a possible cause of the shifting,
spoke-like formations seen in the rings by Voyager 2. But nobody thought
it would be possible to detect the impacts so directly.

Cassini's close-up observations have produced a wealth of new
information about Saturn's ring system, including complex details in the
shapes and spacing of bands that have already revealed signs of three
new moons - in addition to the three other moons Cassini had already
discovered further out.

The craft's discovery of one of the new moons, and a thin ring near the
so-called F-ring, were reported by the International Astronomical Union
on Monday.
Received on Tue 09 Nov 2004 08:34:45 PM PST