If it had a metallic exterior or regular geometry....
If Amalthea had a metallic exterior or regular geometry then it would be a prime candidate for my nut theory about ET's spent decellerator stages. However Amalthea looks like a garden variety rock. I suspect(?) it's a Kuiper belt object that was recently captured. It's so close to Jupiter that there could be all sorts of funky interactions between Amalthea despinning and circularizing its orbit. Too bad its exterior is not metallic.....
Gary
p.s. In all seriousness, we should be discovering wrecked ET hardware about now. Where is it? This is a more profound nondiscovery than SETI's failure.