Instant death puzzles have no place in a Metroid game. Acid pools, 300-foot falls that make you have to climb all the way up again, deadly spike plants, these are all standard Metroid fare.
Instant death puzzles are not.
Anywho... I'm stuck now. I've been to all four planets/space stations and collected the 4 octoliths there. I'll keep exploring; there's probably something I missed, but I was expecting something a bit more climactic for the halfway point.