While Mars-Pluto aspects in Solar Return imply actions that are unconsciously motivated.
Mars-Neptune aspects in Solar Return indicate actions which have no obvious motivation at all, or which involve a great deal of uncertainty or confusion as to direction, goal, timing, and the possibility of success. Actions may entail an act of faith or be totally aimless. For those who are spiritually minded, this can be a test of trust. You know deep down that you are to proceed, but cannot explain your motivation.