I think the problem you are having is due to the fact that
Solar System is a 'Coast/Ocean' feature and that the default Extraction Facility improvement is setup to be used on 'land' only.
Since improvements can't (by default) be set to be Build on both 'water' and 'land' (even though they can be forced to exist on both), I would suggest trying to make a second Extraction Facility.
Quick HowTo:
CIV4ImprovementInfos.xml (Terrain folder)
- copy existing <ImprovementInfo> <Type>IMPROVEMENT_EXTRACTION_FACILITY ... </ImprovementInfo>
- rename copy IMPROVEMENT_EXTRACTION_FACILITY2
- change <bWater> to 1
CIV4BuildInfos.xml (Units folder)
- copy existing <BuildInfo> <Type>BUILD_EXTRACTION_FACILITY ... </BuildInfo>
- rename copy BUILD_EXTRACTION_FACILITY2
- change <ImprovementType> to BUILD_EXTRACTION_FACILITY2
CIV4UnitInfos.xml (Units folder)
- locate <Type>UNIT_CONSTRUCT_SHIP
- copy existing <Build> <BuildType>BUILD_EXTRACTION_FACILITY ... </Build>
- rename copy BUILD_EXTRACTION_FACILITY2
Enjoy (hopefully

)