Quick Time Movie for PIA06243 Cassini's First Close Brush with Hyperion (Animation)
This movie sequence provides the record of Cassini's first close brush
with Hyperion, Saturn's chaotically tumbling moon. As the spacecraft
whizzes past, Hyperion's unusual shape is most apparent. The jagged
outlines are indicators of large impacts chipping away at Hyperion's
shape as a sculptor does to marble.
Hyperion's unusual dimensions are 328 by 260 by 214 kilometers (204 by 162 by 132 miles).
These Cassini images are the best views yet of one of the large,
low-density objects that orbit Saturn. Hyperion is close to the size
limit where, like a child compacting a snowball, internal pressure due to
the moon's gravity will begin to crush weak materials like ice, closing
pore spaces and eventually creating a more spherical shape.
However, this moon has a very irregular shape and preliminary estimates
of its density show that it is only about 60 percent as dense as solid
water ice. This suggests that much of its interior (40 percent or more)
must be empty space.
The low density further suggests that Hyperion is mostly made of water
ice, with a low rock and metal content. If the moon had significant
higher density components, its implied porosity would be significantly
higher than 50 percent. The dark material on the surface is therefore
likely a minor component, possibly originating from impacts of dark
material, as seen on Iapetus.
Hyperion's elliptical orbit and irregular shape influence its chaotic
tumbling. Further, because it is in a resonance orbit with the giant moon
Titan, impact debris ejected with sufficient energy does not come to rest
again on Hyperion. Instead, debris is tugged gravitationally into Titan's
orbit, where it impacts the large smoggy moon.
This series of 25 images was taken over a period of nearly two and a half
days, between June 9 and June 11, 2005, as Cassini's orbit took it close
to Hyperion.
Cassini will have one close, targeted flyby of Hyperion on September 26,
2005.
At the beginning of the movie Cassini was approximately 815,000 kilometers
(506,000 miles) from Hyperion; at the end, the spacecraft was 327,000
kilometers (203,000 miles) distant. The closest image was acquired from a
distance of 168,000 kilometers (104,000 miles). The images were taken
using the narrow-angle camera and a spectral filter sensitive to
ultraviolet wavelengths centered at 338 nanometers. Image scale ranges
from 5 kilometers (3 miles) per pixel at most distant to 1 kilometer
(0.6 mile) at best. The images have been enhanced to improve the
visibility of surface features.
A stereo (3D) version of the image from this encounter is also available (see
PIA06244).
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 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.
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov.
For additional images visit the Cassini imaging team homepage http://ciclops.org.
