In the past 40 years, space flight has encountered all sorts of failure modes. Propulsion systems have leaked and exploded. Power systems have short-circuited. Observation instruments have failed to work or have been pointed in wrong directions. But until this year no CFIT had occurred in outer space.Then, on 23 September, through a series of still-baffling errors, flight controllers at the Jet Propulsion Laboratory, a California Institute of Technology facility under contract to NASA, sent erroneous steering commands to the Mars Climate Observer as it neared the target planet. Obeying blindly like all true robots, the probe, metaphorically speaking, marched off the cliff and was destroyed.