Just don't expect to see celestial fireworks. Next week's impact
near the moon's north pole by the washing machine-sized
spacecraft won't carve a gaping crater or kick up a lot of
debris. And it'll be dark when it happens. "We are not expecting
a big flash or a big explosion" that will be visible from Earth,
said mission chief scientist Maria Zuber of the Massachusetts
Institute of Technology. Still, it'll mark a violent end to a
successful mission that has produced the most high-resolution
gravity maps of Earth's closest neighbor. On Friday, engineers
will turn off the science instruments in preparation for
Monday's finale. Previous unmanned trips to the moon have
studied its lumpy gravitational field, but Ebb and Flow are the
first ones dedicated to this goal. Since entering orbit over New
Year's weekend, the formation-flying spacecraft have peered past
the craggy surface into the interior. Initially, the spacecraft
flew about 35 miles above the surface and later dropped down to
14 miles. About an hour befo