And water that contains an oxidizer...
Toxin in soil may mean no life on Mars
From Miles O'Brien and Kate Tobin
CNN
(CNN) -- NASA's Phoenix lander has discovered a toxic chemical in soil near Mars' north pole, dimming hopes for finding life on the Red Planet, the probe's operators said Monday.
The chemical, perchlorate, is an oxidant widely used in solid rocket fuel. Researchers are still puzzling over the results and checking to make sure the perchlorate wasn't carried to Mars from Earth, the University of Arizona-based science team said.
Since there’s a budding drive to ban perchlorate in rockets (IOW, a Luddite / Socialist drive to end US spaceflight), this story about the precipitate will probably be fodder at some point (soon), and this “make sure the perchlorate wasn’t carried to Mars” sounds like the beginning of it.