[AstralTraveller (David)]

Well the big news wasn't poo, it was perchlorate - ClO4 (2minus) [boy, would subscripts and superscripts be useful!]. This is a strong oxidizing agent which will attack organic material and so be harmful to Earth-like life forms. It is also used in rocket engines as a source of oxygen and so its presence may be due to contamination by the Phoenix lander itself.

The tame relative of perchlorate, chlorite (ClO2) is used in common household bleach and toilet cleaners because it will also attack organic matter but is not as aggressive.

Full story at http://www.nasa.gov/mission_pages/ph...-20080804.html