[meteorite-list] Cassini Spacecraft 'Sandblasted' by Dust from Saturn System in 2004

[Ron Baalke]

Office of News Services
University of Colorado-Boulder
Boulder, Colorado

Contact:
Mihaly Horanyi, (303) 492-6903, horanyi at argos.colorado.edu
Jim Scott, (303) 492-3114

Jan. 19, 2005

Note to Editors: Contents embargoed until 1 p.m. EST on Wednesday, Jan. 19.

Cassini Spacecraft "Sandblasted" By Dust From Saturn System In 2004

New results from the Cassini mission indicate the spacecraft was pelted with 
sporadic bursts of interplanetary dust as it approached Saturn last year, 
according to a University of Colorado at Boulder space scientist.

Mihaly Horanyi of CU-Boulder's Laboratory for Atmospheric and Space Physics said 
the dust particle bursts grew more frequent and intense as the Cassini 
spacecraft closed in on the planet from 40 million miles away in early 2004. 
Horanyi, also a CU-Boulder physics professor, said the dust might have escaped 
into space from the planet's outer "A" ring or perhaps its icy moons, Dionne and 
Rhea.

A paper on the subject was published in the Jan. 20 issue of the journal Nature. 
In addition to Horanyi, authors include Sascha Kempf, Ralf Srama, Stefan 
Helfert, Georg Moragas-Klostermeyer and Eberhard Grun of Germany's Max Planck 
Institute, and Marcia Burton and Mou Roy of NASA's Jet Propulsion Laboratory.

Prior to 1993, researchers believed such interplanetary dust particles were made 
up of primitive material originating from interstellar space, asteroid 
collisions or from comets whizzing through the solar system, Horanyi said.

But in 1993, Horanyi and colleagues found that peculiar bursts of microscopic 
dust observed streaming from the Jupiter region by the Ulysses spacecraft were 
emanating from the volcanic plumes of Io, a moon of Jupiter. "That was the first 
indication that dust can escape from planetary systems," he said.

The dust particles escaping from the Saturn system also are microscopic in size, 
ranging from one-tenth of a micron to one-hundredth of a micron, he said.

"Grains larger than that would be dominated by the gravity of the planet, while 
smaller grains would be dominated by the electromagnetic fields. Only those 
within these size limits can escape the system."

The dust detector aboard Cassini collects electrical signals from each grain of 
dust it traps, allowing scientists to infer the mass and speed of the particles, 
he said. "The energetics of the dust particles indicate that the A ring of 
Saturn is a good candidate for the origin of the dust," Horanyi said.

The burst-like phenomenon of dust grains -- which were traveling at an 
astounding 60 miles per second -- was due to the planet's magnetic field and the 
solar wind "bending" the dust trajectories as they streamed from the Saturn 
system, he said. "The dust is probably coming from the Saturn system at a fairly 
constant rate, but the spacecraft was not always in the right place to detect 
it," he said.

Horanyi also is a member of a CU-Boulder team that has designed and built a dust 
detector to fly on NASA's 2006 New Horizons mission to Pluto. The New Horizons 
instrument, designed and built primarily by students, is expected to provide new 
information on the structure and early formation of the solar system.

An identical instrument also built by LASP will be launched in September 2006 on 
the Aeronomy of Ice in the Mesosphere, or AIM, mission to monitor the dust 
influx into Earth's atmosphere, he said.