Working with Charles Cockell, an astrobiologist at Edinburgh, Wadsworth looked at what happened to Bacillus subtilis, a common soil bacterium and regular Earthly contaminant found on space probes, when it was mixed with magnesium perchlorate and blasted with ultraviolet rays similar to those witnessed on Mars. She found that the bugs were wiped out twice as fast when perchlorate was present. Other perchlorates found on Mars had a similar bactericidal effect.
Further tests found that the UV rays broke down the perchlorate into other chemicals, namely hypochlorite and chlorite, and it is these that appear to be so destructive to the bacteria.
The scientists followed-up with another round of experiments that looked at the toxic effects of iron oxides and hydrogen peroxide, which are also found in Martian soil. These tests yielded even more bad news for microscopic Martians: when the bacteria were hit with UV rays in the presence of perchlorates, iron oxide and peroxide, the bugs were killed 11 times faster than with perchlorates alone. Writing in Scientific Reports, the researchers say that the inhospitable conditions on Mars are caused by a “toxic cocktail of oxidants, iron oxides, perchlorates and UV irradiation.”
This is not the Mars Edgar Rice Burroughs had me hoping for.