• The Programmable Artificial Cell Evolution (PACE) project mentioned in our feature on artificial life (12 February, p 28) has, contrary to what the feature said, begun lab experiments, though these do not involve evolution of artificial cells.
• The terrestrial micro-organisms that synthesise methane are archaea, not bacteria as we stated in “A whiff of life on the Red Planet” (19 February, p 6). The archaea are, like bacteria, single-celled organisms that lack a nucleus. They were mistaken for bacteria when first discovered, but are now recognised as an entirely separate kingdom of life.
• Data tracks on computer hard discs lie in concentric circles, not a spiral as we stated (26 February, p 26). CDs, however, do have spiral tracks.
• We failed to check what turned out to be a spoof report when we said (12 February, p 34) that a Segway transporter was used in a drive-by shooting in Los Angeles in February 2004. Sorry.
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