The continuing seesaw of evidence for and against life on Mars (past or present) took another swing back toward the negative today when NASA announced new findings from the Opportunity rover. While both rovers on Mars continue to accumulate compelling evidence that the planet was once awash with water, the data from Opportunity seems to suggest that this water would have been very salty and acidic, which would be far from ideal for live to prosper. However, let's not get too despondent. News stories published today all seem to be keen to headline the negative, but read the details and it's not at all cut and dry. Yes, the water would have been pretty nasty, but Rover team member Dr Andrew Knoll is reported as saying "It was really salty - in fact, it was salty enough that only a handful of known terrestrial organisms would have a ghost of a chance of surviving there when conditions were at their best." So not a slam-dunk for the absence of life. Something could have survived, and lets not forget either that Opportunity has surveyed a tiny fraction of the land surface of Mars. Were an alien probe to land in some of the truly inhospitable locations on earth, it would send back gloomy messages as well. This case is definitely not closed.