Extraordinary claims require extraordinary evidence, as
astronomer Carl Sagan once said. Sagan was talking about UFOs
and aliens, but his words now stand as a watchword for
skepticism in science. But how do we know when a claim is
extraordinary? Say, maybe when the aliens don't arrive from
space? Consider the controversial "arseniclife", short for
arsenic-based life, bacteria study. Rather than arriving on a
UFO, the microbe was unveiled at NASA headquarters, announced at
an "astrobiology" news briefing on Dec. 2, 2010, as "the first
known microorganism on Earth able to thrive and reproduce using
the toxic chemical arsenic." Arsenic is a poison. How did the
finding that the bacteria called GFAJ-1 replaced phosphorus, a
basic chemical constituent of biochemistry, with arsenic even in
its DNA make its way into the hallowed journalScience, and onto
the stage at NASA? The idea turned out to be too good to be
true, as two studies also published by Science that refuted the
claim showed this summer. Both showed that