On the New Scientist website there's an interesting article about the Viking landers and some new interpretations of their Mars soil sampling. According to some researchers, there's two possible interpretations of the Viking data which support the current existence of microbial life on Mars. The first is that the landers simply didn't have sensitive enough sensors to find life in the first place. Using the same system on the Viking mission, researchers found that they couldn't detect life in some locations here on Earth, which certainly do contain life.

In some soils – including samples taken from Rio Tinto in Spain, which contain iron compounds similar to those detected in Mars soils by NASA's rover Opportunity, the sensitivity of the GCMS was actually a million times lower than its claimed threshold for detection.

The second interpretation is that microbes in Mars may have evolved to use water and hydrogen peroxide as an intracellular fluid, rather than just water, as Earth organisms do. This possibility would not only explain the low level of organics detected, since they would be oxidized by the hydrogen peroxide, and the high reactivity of the soil, it would also give the organisms a greater ability to maintain liquid in their cells at very cold temperatures.

It's amazing how we're still debating the results of experiments that were carried out so long ago. It certainly looks like the latest results may shed some light on the mysterious results obtained by the landers and boost the idea that there's currently life on Mars at the same time.