One of the coauthors here Bada is working on an improved organic detector that will probably be sent on upcoming lander missions (it's not on the 2003 MER landers):

Life on Mars? Before We Go, We've Got To Know
By Greg Clark (<--- That's not me.)
Staff Writer
posted: 08:30 am ET
09 December 1999
http://www.space.com/news/heds03_mod_991209.html

It's supposed to be thousands of times more sensitive to organics than the Viking GCMS. I'd like to see Bada do tests with the MOD detector on the Atacama Desert samples. My guess is he would find some organics in those samples the GCMS-like instrument said were sterile.
BTW, I'm researching the possibility that a recently discovered microorganism may be the cause of the results found by the Viking biology experiments. Interestingly, the enviromental conditions in Atacama may support the existence of this microbe as well. Specific searches for it might therefore detect it in Atacama.
Details soon.

Bob Clark