Amalthea, the Largest of the Four Innermost Satellites of Jupiter

Amalthea, the largest of the four innermost satellites of Jupiter, has a distinct reddish color. What is the origin of this?

A) material from volcanic plumes on Io
B) iron oxide (rust) in the rocks on the surface (like Mars)
C) colors produced in the aurora created when Amalthea passes through the intense magnetic field from Jupiter
D) particles carried to Amalthea from Jupiter across the intense magnetic field tube connecting the two bodies