[meteorite-list] Cassini Observes Meteors Colliding With Saturn's Rings

[Ron Baalke]

April 25, 2013

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

Jia-Rui C. Cook 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-0850 
jccook at jpl.nasa.gov 

RELEASE: 13-120

NASA PROBE OBSERVES METEORS COLLIDING WITH SATURN'S RINGS

WASHINGTON -- NASA's Cassini spacecraft has provided the first direct 
evidence of small meteoroids breaking into streams of rubble and 
crashing into Saturn's rings. 

These observations make Saturn's rings the only location besides 
Earth, the moon, and Jupiter where scientists and amateur astronomers 
have been able to observe impacts as they occur. Studying the impact 
rate of meteoroids from outside the Saturn system helps scientists 
understand how different planet systems in the solar system formed. 

Our solar system is full of small, speeding objects. Planetary bodies 
frequently are pummeled by them. The meteoroids at Saturn range from 
about one-half inch to several yards (1 centimeter to several meters) 
in size. It took scientists years to distinguish tracks left by nine 
meteoroids in 2005, 2009 and 2012. 

Details of the observations appear in a paper in the Thursday edition 
of Science. 

Results from Cassini already have shown Saturn's rings act as very 
effective detectors of many kinds of surrounding phenomena, including 
the interior structure of the planet and the orbits of its moons. For 
example, a subtle but extensive corrugation that ripples 12,000 miles 
(19,000 kilometers) across the innermost rings tells of a very large 
meteoroid impact in 1983. 

"These new results imply the current-day impact rates for small 
particles at Saturn are about the same as those at Earth-- two very 
different neighborhoods in our solar system, and this is exciting to 
see," said Linda Spilker, Cassini project scientist at NASA's Jet 
Propulsion Laboratory (JPL) in Pasadena, Calif. "It took Saturn's 
rings acting like a giant meteoroid detector -- 100 times the surface 
area of the Earth -- and Cassini's long-term tour of the Saturn 
system to address this question." 

The Saturnian equinox in summer 2009 was an especially good time to 
see the debris left by meteoroid impacts. The very shallow sun angle 
on the rings caused the clouds of debris to look bright against the 
darkened rings in pictures from Cassini's imaging science subsystem. 

"We knew these little impacts were constantly occurring, but we didn't 
know how big or how frequent they might be, and we didn't necessarily 
expect them to take the form of spectacular shearing clouds," said 
Matt Tiscareno, lead author of the paper and a Cassini participating 
scientist at Cornell University in Ithaca, N.Y. "The sunlight shining 
edge-on to the rings at the Saturnian equinox acted like an 
anti-cloaking device, so these usually invisible features became 
plain to see." 

Tiscareno and his colleagues now think meteoroids of this size 
probably break up on a first encounter with the rings, creating 
smaller, slower pieces that then enter into orbit around Saturn. The 
impact into the rings of these secondary meteoroid bits kicks up the 
clouds. The tiny particles forming these clouds have a range of 
orbital speeds around Saturn. The clouds they form soon are pulled 
into diagonal, extended bright streaks. 

"Saturn's rings are unusually bright and clean, leading some to 
suggest that the rings are actually much younger than Saturn," said 
Jeff Cuzzi, a co-author of the paper and a Cassini interdisciplinary 
scientist specializing in planetary rings and dust at NASA's Ames 
Research Center in Moffett Field, Calif. "To assess this dramatic 
claim, we must know more about the rate at which outside material is 
bombarding the rings. This latest analysis helps fill in that story 
with detection of impactors of a size that we weren't previously able 
to detect directly." 

The Cassini-Huygens mission is a cooperative project of NASA, the 
European Space Agency and the Italian Space Agency. JPL manages the 
Cassini-Huygens mission for NASA's Science Mission Directorate in 
Washington. JPL designed, developed and assembled the Cassini orbiter 
and its two onboard cameras. The imaging team consists of scientists 
from the United States, England, France and Germany. The imaging 
operations center is based at the Space Science Institute in Boulder, 
Colo. 

For images of the impacts and information about Cassini, visit: 

http://www.nasa.gov/cassini 
	
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