A year and a half ago, NASA announced that one of its
scientists, Felisa Wolfe-Simon, had found a bacterium that could
use arsenic instead of phosphorus in its DNA. This revelation,
published in Science, had enormous implications for our
understanding of what’s necessary for life—we’ve always thought
phosphorus was essential and arsenic poisonous, and having that
disproven might mean life could exist in environments where it
had been thought impossible. Almost immediately, though,
scientists and science journalists began to pick apart this
paper. DISCOVER blogger Carl Zimmer rounded up the case against
in a Slate article shortly after the paper’s publication. Ever
since, he’s kept track of the story’s evolution—including
experiments posted by microbiologist Rosie Redfield on her blog
that provided evidence against the claim—here on his blog. All
the way along, Wolfe-Simons refused to comment on Redfield’s
experiments, saying she would wait until they were published by
a peer-reviewed journal. Now, Redfield’s