At roughly 12:30AM ET early on Friday morning, a soda machine-sized NASA spacecraft slammed into the far side of the moon at 3,600 miles per hour. The impact was entirely planned by NASA engineers in order to conclude the Lunar Atmosphere and Dust Environment Explorer (LADEE) program, which launched late last year. After studying the composition of the lunar atmosphere for months, the spacecraft didn't have the fuel to continue flight and engineers decided it was best to place it down on the far side of the moon, out of sight and far from previous historic landing sites.
During six months of research, the spacecraft performed careful analysis of the lunar atmosphere. One of its discoveries was finding trace amounts of water in the atmosphere. However, NASA wasn't able to answer a decades-long question that it hoped to solve over the course of the mission. NASA was looking to explain reports from Apollo astronauts of an aurora borealis-like glow on the horizon just before sunrise. Scientists hypothesized that dust particles in the thin lunar atmosphere accounted for the reports, but the spacecraft was unable to confirm that was the case. Nevertheless, NASA was able to complete its analysis of the atmosphere and therefore the (relatively inexpensive) $280 million mission was a success.
Correction: One of NASA's primary goals for the LADEE mission was to investigate reports of a glow on the horizon, and while mission engineers weren't able to definitively explain the phenomenon, the spacecraft was successfully able to study the atmosphere. The mission therefore accomplished its goals — a previous version of this article was unclear on that point.