Measurements from the Vikings in the '70's, suggested taht the environment on Mars would be too ixidating to support any life. But new analysis af samples from the Phoenix lander, shows that the oxidation-reduction potential of the soil is only moderate.

Martian soils. Some Viking measurements indirectly suggested that the soils contained highly oxidizing compounds, which could present extremely harsh conditions for life. But recent observations from the Phoenix Mars Mission pointed to evidence of perchlorate, a potentially highly oxidizing compound, in the Martian soils.

However, some studies have noted that because perchlorate is highly stable, its presence in Martian soils cannot explain the Viking measurements. Quinn et al. (2011) present a new analysis of Mars soil samples using the Wet Chemistry Laboratory, a component of the Microscopy, Electrochemistry, and Conductivity Analyzer on the NASA Mars Phoenix Lander.

They found that although low levels of oxidizing compounds may be present, the oxidation-reduction potential of the soil is moderate and well within the range expected for habitable soils.

Source: Geophysical Research Letters