At a press conference on 10 December, officials reported that Akatsuki's engines fired for less than three minutes, far less than what was required to enter into Venus orbit. Further research found that the likely reason for the engine malfunction was salt deposits jamming the valve between the helium pressurization tank and the fuel tank. As a result, engine combustion became oxidizer-rich, with resulting high combustion temperatures damaging the combustion chamber throat and nozzle.
I was wondering what would potentially cause salt buildups in the craft, especially in such a location as "the valves" and which valves? Was the salt a by-product of the specific combustion materials? It quotes an additional event "like this one" as:
A similar vapor leakage problem destroyed the NASA Mars Observer probe in 1993.
I guess my three questions here are:
Were these due to the same reaction? What reaction caused salt deposits on Akatusuki? And why would salt deposits cause the engines to run oxidzer-rich?
Note: Akatuski performed a recovery burn and reached its intended objective after the failure.