Yesterday, NASA’s GRAIL (Gravity Recovery and Interior Laboratory) twin spacecraft Ebb and Flow ended their mission by crashing on the Moon.

Their final maneuver was initiated on December 14, when almost all the propellant still available for Ebb and Flow was used to change their orbit lowering it even more than it already was. In this way, the trajectory of the GRAIL spacecraft was directed to a mountain near the Moon’s north pole.

The mission of Ebb and Flow lasted almost until the last minute as less than an hour before the impact the two GRAIL spacecraft started a rocket burn that went on until they ran out of propellant. This maneuver was intended to determine exactly how much propellant they still had in their tanks, a piece of data that’s added a huge amount obtained during this mission. This is not mere curiosity but information that will help NASA engineers to improve computer models regarding propellant needs for future missions.

The decision to destroy Ebb and Flow generated a controversy among a part of the public who read the news. Even if it’s a sad choice it was the right one. The GRAIL project manager at JPL David Lehman said that NASA wanted to avoid any risk that the GRAIL spacecraft might crash on one of the sites of the past lunar missions. The odds of hitting one of those historical places were very low but it was right to have zero risk.

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The impact of Ebb and Flow occurred at 30 seconds from each other. It was a complete success, like the whole mission. Just a few days ago, NASA showed the first gravitational maps of the Moon obtained from data sent by the GRAIL spacecraft but the study of the enormous lot of data will go on, particularly of the more accurate data sent during their extended mission.

The site of Ebb and Flow impact was named Sally K. Ride Impact Site in honor of the first American woman to travel in space, who unfortunately passed away last July. The choice is not accidental because Sally Ride founded Sally Ride Science, a company that aims to produce scientific material for educational use, and worked with the GRAIL mission.

The MoonKAM (Moon Knowledge Acquired by Middle School Students), the camera that each of the GRAIL spacecraft was provided, took more than 115,000 photographs of the Moon in areas chosen by students in American schools. This secondary mission was directed by Sally Ride, another success for a mission of great scientific value which has also involved the students, who are the new generations that hopefully one day will be able to regularly travel in space.