[meteorite-list] Cassini's Flyby of Phoebe Shows a Moon With a Battered Past

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sat Jun 12 22:41:49 2004
Message-ID: <200406130241.TAA14953_at_zagami.jpl.nasa.gov>

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Heidi Finn (720) 974-5859
Cassini Imaging Central Laboratory for Operations
Space Science Institute, Boulder, Colo.

News Release: 2004-147 June 12, 2004

Cassini's Flyby of Phoebe Shows a Moon With a Battered Past

First images from the Cassini flyby of Phoebe reveal it to be a
scarred, cratered outpost with a very old surface and a
mysterious past, and a great deal of variation in surface
brightness across its surface.

"What spectacular images," said Dr. Carolyn Porco, Cassini
Imaging Team leader at the Space Science Institute in Boulder,
Colo. "So sharp and clear and showing a great many geological
features, large and small. It's obvious a lot of new insights
into the origin of this strange body will come as a result of all
this."

"What we are seeing is very neat. Phoebe is a heavily cratered
body. We might be seeing one of the chunks from the formation of
the solar system, 4.5 billion years ago. It's too soon to say,"
said Dr. Torrence Johnson, Cassini imaging team member at NASA's
Jet Propulsion Laboratory, Pasadena, Calif. "It's important to
see the big picture from all of the other instruments to get the
global view on this tiny moon."

Dr. Gerhard Neukum, an imaging team member from Freie University
in Berlin, said, "It is very interesting and quite clear that a
lot of craters smaller than a kilometer are visible. This means,
besides the big-ones, lots of projectiles smaller than 100 meters
(328 feet) have hit Phoebe." Whether these projectiles came from
outside or within the Saturn system is debatable.

There is a suspicion that Phoebe, the largest of Saturn's outer
moons, might be parent to the other, much smaller retrograde
outer moons that orbit Saturn.

Dr. Joseph Burns, an imaging team member and professor at Cornell
University, Ithaca, N.Y. said, "Looking at those big 50
kilometers (31 mile) craters, one has to wonder whether their
impact ejecta might be the other tiny moons that orbit Saturn on
paths much like Phoebe's."

All planned 11 instruments operated as expected and all data was
acquired. Scientists plan to use the data to create global maps of
the cratered moon, and to determine Phoebe's composition, mass and
density. It will take scientists several days to pour over the data
to make more concrete conclusions.

Cassini came within approximately 2,068 kilometers (about 1,285
miles) of the dark moon on Friday, June 11. The spacecraft was
pointing its instruments at the moon during the flyby. Several
hours later it turned to point its antenna to Earth. The signal
was received through the Deep Space Network antennas in Madrid,
Spain and Goldstone, in California's Mojave Desert, at 7:52 a.m.
PDT today. Cassini was traveling at a relative speed of 20,900
kilometers per hour (13,000 miles per hour) relative to Saturn.
It's been 23 years since a spacecraft last visited Phoebe. The
Voyager 2 flyby in 1981 was at a distance from 2.2 million
kilometers, (about 1.4 million miles), 1,000 times farther away.

With the Phoebe accomplished, Cassini is on course for Saturn. A
trajectory correction maneuver is scheduled for June 16. Cassini
will conduct a critical 96-minute burn before going into orbit
around Saturn on June 30 (July 1 Universal Time). During Cassini's
planned four-year tour it will conduct 76 orbits around the Saturn
system and execute 52 close encounters with seven of Saturn's 31
known moons.

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet
Propulsion Laboratory, a division of the California Institute of
Technology in Pasadena, manages the Cassini-Huygens mission for
NASA's Office of Space Science, Washington, D.C. The Cassini
orbiter and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team is based at the Space Science
Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission, visit

http://saturn.jpl.nasa.gov/index.cfm

and the Cassini imaging team home page,

http://ciclops.lpl.arizona.edu/ .

                              -end-
Received on Sat 12 Jun 2004 10:41:36 PM PDT