Ziggy is Homo-Superior (the coming race).
Any road up I'd be interested to see if there is any direct connection between the end of Prometheus and the last flight of the Nostromo.
Was Nostromo diverted on it's return journey to Acheron because of a company suit unearthing information about the earlier story?
Ash was put onboard the ship before take off so it seems unlikely to me that it was a standard Ore collection that by fluke discovered the derelict's signal.