Nice article. Thanks for the link.
I like the fact in the paper itself the authors cite Levin's work. They also refer to work that suggests liquid water could exist on Mars for short periods. They cite as well the experiments that show the Viking GCMS experiment was insensitive to low numbers of microbes.
I have some quibbles with the press release however. The paper itself shows at least endospores could survive the strongest oxidant suggested to exist on Mars and UV radiation with a 5 mm cover of soil. It seems therefore the phrasing of the news release should be changed.
The paragraph:

"Soil on Mars is thought to be rich in oxidising chemicals that are known to destroy life. The high levels of ultraviolet radiation on the surface of the planet make it unlikely that any organism could survive. Ronald Crawford and colleagues from the University of Idaho have investigated whether bacterial endospores can exist in Mars's hostile environment"

should be changed to indicate that it USED to be believed these conditions were inimical to life, but the new Crawford experiments cast doubt on this idea. And furthermore this means the biology explanation of the Viking life experiments should be given just as much credance as the non-life explanations.

Bob Clark