Lyric discussion by noirling 

Cover art for Tombstone lyrics by Midnight Juggernauts

I don't think Songmeaning1's interpretation is entirely correct. Drawing from the songs alone, it sounds like the album has to do with the destruction of mankind, but not necessarily by alien hands.

The lyrics of this song are spoken as if through some technological vocoder, as if an advanced society came upon some object and couldn't tell what it was. They determine that it is a Tombstone. The end of human civilization.

I fail to see where aliens have anything to do with this. They have not been mentioned in any of the songs on the album.