More strangely, the Spirit had no memory of what it had done for that part of Sol 1800. The rover did not record actions, as it otherwise always does, to the part of its computer memory that retains information even when power is turned off, the so-called nonvolatile memory. "It's almost as if the rover had a bout of amnesia," said John Callas, the project manager for the rovers. Another rover system did record that power was being drawn from the batteries for an hour and a half. "Meaning the rover is awake doing something," Dr. Callas said. But before-and-after images showed that the Spirit ended the day exactly where it started.