The possibility of the perchlorate-metabolizing microbes being present might have a bearing on the failure of the TEGA instrument on Phoenix to detect free chlorine to confirm the presence of perchlorate. The TEGA scientists looked only for chlorine gas. This was based on the fact that free oxygen was detected from one of the samples. However, the perchlorate-metabolizing microbes release oxygen in reducing perchlorate to chlorate, then chlorite,
then chloride. Then what might be needed to search for instead might be one of these compounds.
This would require TEGA being programmed to search for them specifically since in its normal mode of operation it does not do a wide spectrum search but focuses on only certain expected compounds only.

I was also interested to see that CO2 was seen to be evolved in one of the TEGA samples. This could possibly be due to carbonates in some form or it may signal that organics were present but were catalytically decomposed by the iron compounds.
Because of the known decomposing effects of the Mars iron compounds on organics, perhaps some ways need to be explored where this effect could be mitigated in the current TEGA instrument. For instance, estimated amounts of ice in soil in the north polar region from orbital observations could be 25% and above. Perhaps if a high ice containing sample is successfully delivered to TEGA, we could heat the soil first only to the level that would allow this water to remain liquid. Then perhaps the iron compounds would become oxidized and this would reduce the oxidizing effects of the iron compounds on the
organics. This might be helped by free oxygen that was found to be evolved in one of the TEGA samples. Or perhaps the iron compounds would dissolve in water
after a sufficiently long period of time.
Then after the iron-compounds were oxidized or decomposed, the temperatures would be raised to the level to volatilize the organics and detect them then.

Bob Clark