[MIham] OT NASA News On Jupiter's And Saturn's Rings

[Duane Fischer, W8DBF]

March 31, 2011

Dwayne C. Brown 

Headquarters, Washington 

202-358-1726 

dwayne.c.brown at nasa.gov 

Jia-Rui Cook 

Jet Propulsion Laboratory, Pasadena, Calif. 

818-354-0850 

jccook at jpl.nasa.gov 





RELEASE: 11-095

NASA SPACECRAFT REVEAL MYSTERIES OF JUPITER AND SATURN RINGS

PASADENA, Calif. -- In a celestial forensic exercise, scientists 

analyzing data from NASA's Cassini, Galileo and New Horizons missions 

have traced telltale ripples in Saturn and Jupiter's rings to 

specific collisions with cometary fragments that occurred decades, 

not millions of years, ago. 

Jupiter's ripple-producing culprit was comet Shoemaker-Levy 9. The 

comet's debris cloud hurtled through the thin Jupiter ring system on 

a collision course into the planet in July 1994. Scientists attribute 

Saturn's ripples to a similar object - likely another cloud of comet 

debris - plunging through the inner rings in 1983. The findings are 

detailed in two papers published Thursday in the journal Science. 

"We're finding evidence that a planet's rings can be affected by 

specific, traceable events that happened in the last 30 years, rather 

than a hundred million years ago," said Matthew Hedman, a Cassini 

imaging team associate, lead author on one of the papers, and a 

research associate at Cornell University in Ithaca, N.Y. "The solar 

system is a much more dynamic place than we gave it credit for." 

Scientists learned about the patchy patterns in Jupiter's rings in the 

late 1990s from Galileo's visit to Jupiter. Unfortunately, the images 

from that mission were fuzzy, and scientists didn't understand why 

such patterns would occur. Not until Cassini entered orbit around 

Saturn in 2004 and started sending back thousands of images did 

scientists have a better picture of the activity. A 2007 science 

paper by Hedman and colleagues first noted corrugations in Saturn's 

innermost ring, dubbed the D ring. 

A group including Hedman and Mark Showalter, a Cassini co-investigator 

based at the SETI Institute in Mountain View, Calif., saw that the 

grooves in the D ring appeared to wind together more tightly over 

time. Playing the process backward, Hedman demonstrated the pattern 

originated when something tilted the D ring off its axis by about 300 

feet (100 meters) in late 1983. The scientists found Saturn's gravity 

on the tilted area warped the ring into a tightening spiral. 

Cassini imaging scientists received another clue around August 2009 

when the sun shone directly along Saturn's equator and lit the rings 

edge-on. The unique lighting conditions highlighted ripples not 

previously seen in another part of the ring system. Whatever happened 

in 1983 was big - not a small, localized event. 

The collision tilted a region more than 12,000 miles (19,000 

kilometers) wide, covering part of the D ring and the next outermost 

ring, called the C ring. Unfortunately, spacecraft were not visiting 

Saturn at that time, and the planet was on the far side of the sun 

out of sight from ground or space-based telescopes. 

Hedman and Showalter, the lead author on the second paper, wondered 

whether the long-forgotten pattern in Jupiter's ring system might 

illuminate the mystery. Using Galileo images from 1996 and 2000, 

Showalter confirmed a similar winding spiral pattern by applying the 

same math they had applied to Saturn and factoring in Jupiter's 

gravitational influence. Galileo was launched on a space shuttle in 

1989 and studied Jupiter until 2003. 

Unwinding the spiral pinpointed the date when Jupiter's ring was 

tilted off its axis between June and September 1994. Shoemaker-Levy 

plunged into the Jovian atmosphere in late July. The Galileo images 

also revealed a second spiral, which was calculated to have 

originated in 1990. Images taken by New Horizons in 2007, when the 

spacecraft flew by Jupiter on its way to Pluto, showed two newer 

ripple patterns, in addition to the fading echo of the Shoemaker-Levy 

impact. 

"We now know that collisions into the rings are very common - a few 

times per decade for Jupiter and a few times per century for Saturn," 

Showalter said. "Now scientists know that the rings record these 

impacts like grooves in a vinyl record, and we can play back their 

history later." 

Launched in Oct. 15, 1997, Cassini began orbiting Saturn in 2004 and 

sends back data daily. 

"Finding these fingerprints still in the rings is amazing and helps us 

better understand impact processes in our solar system," said Linda 

Spilker, Cassini project scientist, based at NASA's Jet Propulsion 

Laboratory in Pasadena, Calif. "Cassini's long sojourn around Saturn 

has helped us tease out subtle clues that tell us about the history 

of our origins." 

The Cassini-Huygens mission is a cooperative project of NASA, the 

European Space Agency and the Italian Space Agency. The mission is 

managed by JPL for NASA's Science Mission Directorate in Washington. 

The imaging team is based at the Space Science Institute in Boulder, 

Colo. For more information about Cassini, visit: 

http://www.nasa.gov/cassini 

Pluto New Horizons launched in 2006 on the first mission to study 

Pluto and the Kuiper Belt. The mission is managed by the Johns 

Hopkins Applied Physics Laboratory in Laurel, Md., for NASA. The 

mission is part of the New Frontiers program managed at the agency's 

Marshall Space Flight Center in Huntsville, Ala. For more information 

about Pluto New Horizons, visit: 

http://www.nasa.gov/newhorizons 



Duane Fischer, W8DBF - WPE8CXO
E-Mail: dfischer at usol.com
Hallicrafters web site: www.w9wze.net
HHRP web site: hhrp.w9wze.net