Compositional maps of Saturn's moon Phoebe from imaging spectroscopy.
The origin of Phoebe, which is the outermost large satellite of Saturn, is of particular interest because its inclined, retrograde orbit suggests that it was gravitationally captured by Saturn, having accreted outside the region of the solar nebula in which Saturn formed. By contrast, Saturn's regular satellites (with prograde, low-inclination, circular orbits) probably accreted within the sub-nebula in which Saturn itself formed. Here we report imaging spectroscopy of Phoebe resulting from the Cassini-Huygens spacecraft encounter on 11 June 2004. We mapped ferrous-iron-bearing minerals, bound water, trapped CO2, probable phyllosilicates, organics, nitriles and cyanide compounds. Detection of these compounds on Phoebe makes it one of the most compositionally diverse objects yet observed in our Solar System. It is likely that Phoebe's surface contains primitive materials from the outer Solar System, indicating a surface of cometary origin.
Clark
Roger N
RN
US Geological Survey, MS964, Box 25046, Federal Center, Denver, Colorado 80225, USA. rclark@usgs.gov
Brown
Robert H
RH
Jaumann
Ralf
R
Cruikshank
Dale P
DP
Nelson
Robert M
RM
Buratti
Bonnie J
BJ
McCord
Thomas B
TB
Lunine
J
J
Baines
K H
KH
Bellucci
G
G
Bibring
J-P
JP
Capaccioni
F
F
Cerroni
P
P
Coradini
A
A
Formisano
V
V
Langevin
Y
Y
Matson
D L
DL
Mennella
V
V
Nicholson
P D
PD
Sicardy
B
B
Sotin
C
C
Hoefen
Todd M
TM
Curchin
John M
JM
Hansen
Gary
G
Hibbits
Karl
K
Matz
K-D
KD