I get press releases from various astronomy sources, and the headlines are usually pretty descriptive. But when you get one that says "Mars surface probably can't support life" you kinda have to say, well duh. It's cold, the Sun's UV zaps the surface, the air is 1% that of Earth's, and what's there is mostly CO2 and argon.
However, another press release was issued about the same topic (sometimes the universities of different team members will produce their own releases), and in it one of the astronomers says:
the intense ultraviolet exposure, the low temperatures, the lack of water and the oxidants in the soil would make it difficult for any microbe to survive on Mars.
... so I feel better.
The story itself is that electrical storms on Mars-- which can be real doozies-- can zap the carbon dioxide and water in the air there and create hydrogen peroxide (H2O2). That will snow down onto the surface, and any little microscopic critter there will get sterilized. When I pour hydrogen peroxide on a cut, it fizzes merrily as it oxidizes bacteria, sending them to the Great Petri Dish in the Sky. So having that toxic stuff snowing down might very well make sure that nothing grows in the martian soil (and by looking at that image above, having giant pluses and minuses flying around can't help either). Bummer.
What's very cool about this idea is that it might explain an old apparent paradox from Viking, the first martian lander. It had some experiments on board that looked for life. One said no, and one said maybe, in seeming contradiction. It may be that the one that said no was because it really didn't detect any organic matter (which is what it was designed to look for), and the one that said maybe might have been because it was detecting the chemical reactivity of hydrogen peroxide, and couldn't distinguish between that and the reactions due to life.
It's not for sure if this is what happened or not. We're sending more probes to Mars, including the Mars Science Lab, which is a monster compared to the two rovers there now. More sophisticated landers will yield a lot more info about the Red Planet, and hopefully answer some of these long-standing questions. If, that is, they can avoid the monster storms, solar UV, low temperatures, H2O2 snowflakes, and of course the giant pluses.