At the time of the mission, the results of the LR experiments were interesting but not conclusive and while this further analysis of the data may lead one to suspect a positive result there are other factors that have to be worked into the calculus of any conclusion.
At the time of the Viking planning and experiment design we did not know that the surface soil of Mars has a high ratio of percholorates. On Earth, percholorates are oxidizers providing oxygen to any reaction. They are frequently used in explosives and rocket propellants.
There is recent research that suggests that Mars has been both cold and arid for a longer period than we may have once thought. James Head, the plenary speaker at the Lunar and Planetary Science conference paints a picture of Mars where temperatures have never risen above freezing in the mid-latitude region of the planet.
The warm-wet verses cold-dry dichotomy has always been a problem for planetary science because if Mars went through a warm-wet period, where did the heat come from?
The Mars Science Laboratory (Curiosity) will touch down in just a little over three months and we'll learn much more about the surface geology and the geologic history during the coarse of the mission.
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