Surface composition of Hyperion.
Hyperion, Saturn's eighth largest icy satellite, is a body of irregular shape in a state of chaotic rotation. The surface is segregated into two distinct units. A spatially dominant high-albedo unit having the strong signature of H2O ice contrasts with a unit that is about a factor of four lower in albedo and is found mostly in the bottoms of cup-like craters. Here we report observations of Hyperion's surface in the ultraviolet and near-infrared spectral regions with two optical remote sensing instruments on the Cassini spacecraft at closest approach during a fly-by on 25-26 September 2005. The close fly-by afforded us the opportunity to obtain separate reflectance spectra of the high- and low-albedo surface components. The low-albedo material has spectral similarities and compositional signatures that link it with the surface of Phoebe and a hemisphere-wide superficial coating on Iapetus.
Cruikshank
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DP
NASA Ames Research Center, MS 245-6, NASA Ames Research Center, MS 211-3, Moffett Field, California 94035, USA. Dale.P.Cruikshank@nasa.gov
Dalton
J B
JB
Dalle Ore
C M
CM
Bauer
J
J
Stephan
K
K
Filacchione
G
G
Hendrix
A R
AR
Hansen
C J
CJ
Coradini
A
A
Cerroni
P
P
Tosi
F
F
Capaccioni
F
F
Jaumann
R
R
Buratti
B J
BJ
Clark
R N
RN
Brown
R H
RH
Nelson
R M
RM
McCord
T B
TB
Baines
K H
KH
Nicholson
P D
PD
Sotin
C
C
Meyer
A W
AW
Bellucci
G
G
Combes
M
M
Bibring
J-P
JP
Langevin
Y
Y
Sicardy
B
B
Matson
D L
DL
Formisano
V
V
Drossart
P
P
Mennella
V
V