The exercise will not be for the advance of science, but rather something of a garbage-disposal operation, to make sure that the probes — which are running out of fuel — do not come to rest in a historically significant place, like on Neil Armstrong’s footprints. The Moon has been affronted this way many times before, especially during the space race of the 1960s, but NASA is now trying to dispose of its litter more carefully. This time, the first impact will come 40 seconds past 5:38 p.m. Eastern Standard Time on Dec. 17 when Ebb slams into a mountain near the Moon’s north pole at 3,760 miles per hour. The second, from Ebb’s twin, Flow, will come 20 seconds later. Unfortunately, since the action will happen on the dark side of the Moon, there will be nothing for earthlings to see."
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