QUESTION:
What type of fuel do Galileo's engines use?

ANSWER from FAQ:
Galileo uses monomethylhydrazine for fuel. The fuel has to be
oxidized in order to ignite, so nitrogen tetroxide is mixed into the
fuel right before a burn. There are two separate tanks of helium
pressurant. In all, Galileo carried 932 kg (2,050 lbs) of propellant
at launch.