Arsenic-based life: How sure are they?

NASA astrobiologist Felisa Wolfe-Simon, who led the team reporting on life that used arsenic as a chemical building block. wrote that she checked her work carefully at every step and was 100% sure when she submitted her paper. Doubters do exist, though. Quite a few doubters, with good credentials of their own, are pointing out where the experiments could have been done better, where contamination could have crept in, and where the results seem odd (the bacteria were grown in water, but arsenic bonds are weak in water.) A NASA spokesperson dismissed criticisms on the web or in blogs, saying they should be published in papers, which raises an interesting question about form v. content making a critique valuable. One of the original paper's authors did agree on this: " The only way this is going to get settled is if people reproduce these experiments on their own.”