[meteorite-list] Spongy-Looking Hyperion Tumbles Into View

[Ron Baalke]

MEDIA RELATIONS OFFICE				
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.		   

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

Image Advisory: 2005-114			July 11, 2005

Spongy-Looking Hyperion Tumbles Into View

Two new Cassini views of Saturn's tumbling moon Hyperion offer 
the best looks yet at one of the icy, irregularly-shaped moons 
that orbit the giant, ringed planet.

The image products released today include a movie sequence and 
a 3D view, and are available at http://saturn.jpl.nasa.gov, 
http://www.nasa.gov/cassini and http://ciclops.org .

The views were acquired between June 9 and June 11, 2005, 
during Cassini's first brush with Hyperion.

Hyperion is decidedly non-spherical and its unusual shape is 
easy to see in the movie, which was acquired over the course of 
two and a half days.  Jagged outlines visible on the moon's 
surface are indicators of large impacts that have chipped away 
at its shape like a sculptor.

Preliminary estimates of its density show that Hyperion is only 
about 60 percent as dense as solid water ice, indicating that 
much of its interior (40 percent or more) must be empty space.  
This makes the moon more like an icy rubble pile than a solid 
body.

In both the movie and the 3D image, craters are visible on the 
moon's surface down to the limit of resolution, about 1 kilometer 
(0.6 mile) per pixel. The fresh appearance of most of these 
craters, combined with their high spatial density, makes Hyperion 
look something like a sponge.

The moon's spongy-looking exterior is an interesting coincidence, 
as much of Hyperion's interior appears to consist of voids.   
Hyperion is close to the size limit where, like a child compacting 
a snowball, internal pressure due to the moon's own gravity will 
begin to crush weak materials like ice, closing pore spaces and 
eventually creating a more nearly spherical shape.

The images used to create these views were obtained with Cassini's 
narrow-angle camera at distances ranging from approximately 815,000 
to 168,000 kilometers (506,000 to 104,000 miles) from Hyperion.  
Cassini will fly within 510 kilometers (317 miles) of Hyperion on 
Sept. 26, 2005.

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 Science Mission Directorate, 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.

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