( CNN ) -- A pair of robotic twins that have been diligently mapping the moon this year went out with a bang Monday . As scheduled , the Gravity Recovery and Interior Laboratory probes Ebb and Flow crashed into a mountain on the moon , ending a fruitful mission to study the surface and composition of the celestial body . `` The two probes were sent purposely into the moon because they no longer had enough altitude or fuel to continue science operations , '' NASA said . The agency named the site where the spacecraft crashed for Sally Ride , the first American woman astronaut in space . She died in July . Ebb and Flow crashed on a mountain near the moon 's north pole at 2:28 p.m. PT and 2:29 p.m. PT at a speed of 3,760 mph , NASA said . They were about the size of a washer and dyer . `` We will miss our lunar twins , but the scientists tell me it will take years to analyze all the great data they got , and that is why we came to the moon in the first place , '' said GRAIL project manager David Lehman of NASA 's Jet Propulsion Laboratory . `` So long , Ebb and Flow , and we thank you . '' Thanks to GRAIL , scientists now have the highest-resolution gravity field map of any celestial body , NASA has said . That means the probes have been making a high-quality map of the gravitational field of the moon , giving scientists unprecedented insight into what 's below the surface and how the moon may have formed . Results from this mission have delivered several other important findings , principal investigator Maria Zuber of the Massachusetts Institute of Technology told reporters last week . These include : . -- Evidence that the crust of the moon is much thinner than scientists believed . -- Some of the large impact basins dug into the moon 's mantle , which is useful because scientists want to understand the moon 's composition . It is believed that the composition of the Earth 's mantle is similar to that of the moon . -- The moon 's crust is much more fractured than scientists thought . -- It appears the crusts of planets , including Mars , have been bombarded in a similar way . If there was water on Mars , as scientists believe there may have once been , where would it have gone ? GRAIL , looking at the moon , provides a clue : . `` These fractures provide a pathway deep inside the planet , and it 's very easy to envision now how a possible ocean at the surface could have found its way deep into the crust of a planet , '' Zuber said . Another major finding : large , lava-filled cracks ( dykes ) , which are hundreds of miles long and exist about 6 miles below the surface . There 's no record of them at the surface of the moon . `` These dykes actually provide evidence for early expansion of the moon shortly after it formed , '' Zuber said . `` This had been predicted by models , but no evidence had been found . '' CNN 's Elizabeth Landau contributed to this report .
GRAIL probes Ebb and Flow crash into a mountain near the moon 's north pole . The site is named for the late American astronaut Sally Ride , who died in July . The probes have been diligently mapping the moon and collecting evidence this year .