Compositional maps of Saturn's moon Phoebe from imaging spectroscopy

Area of Science:

• Planetary Science
• Astrobiology
• Solar System Exploration

Background:

• Phoebe, Saturn's outermost large moon, has an unusual inclined, retrograde orbit.
• This orbit suggests Phoebe was gravitationally captured by Saturn.
• Its capture implies accretion outside Saturn's formation region, unlike regular satellites.

Purpose of the Study:

• To investigate the composition of Phoebe using data from the Cassini-Huygens spacecraft.
• To understand Phoebe's origin and its implications for early Solar System materials.

Main Methods:

• Imaging spectroscopy during the Cassini-Huygens spacecraft encounter on June 11, 2004.
• Mapping of surface composition, including minerals and organic compounds.

Main Results:

• Detected ferrous-iron-bearing minerals, bound water, and trapped carbon dioxide (CO2).
• Identified probable phyllosilicates, organics, nitriles, and cyanide compounds on Phoebe's surface.
• Phoebe exhibits remarkable compositional diversity, one of the most diverse objects in the Solar System.

Conclusions:

• Phoebe's surface likely contains primitive materials from the outer Solar System.
• The composition suggests a cometary origin for Phoebe.
• This finding provides insights into the early Solar System's composition and satellite formation processes.