PASADENA, Calif. - A pair of NASA spacecraft crashed into a mountain near the moon's north pole on Monday, bringing a deliberate end to a mission that peered into the lunar interior.
Engineers commanded the twin spacecraft, Ebb and Flow, to fire their engines and burn their remaining fuel. Ebb plunged first followed by Flow about 30 seconds later.
Afterward, NASA said it had dedicated the final resting spot in honor of mission team member, Sally Ride, the first American woman in space who died earlier this year. By design, the impact site was far away from the Apollo landings and other historical sites.
Ride's sister, who huddled in the NASA control room for the finale, said it might be time to dust off Ride's first telescope to view the newly named site.
"We can look at the moon with a new appreciation and a smile in the evening when we see it knowing that a little corner of the moon is named after Sally," the Rev. Bear Ride said in an interview.
Since the back-to-back crashes occurred in the dark, they were not visible from Earth. The Lunar Reconnaissance Orbiter circling the moon will pass over the mountain and attempt to photograph the skid marks left by the washing machine sized-spacecraft as they hit the surface at 3,800 mph.
After rocketing off the launch pad in September 2011, Ebb and Flow took a roundabout journey to the moon, arriving over the New Year's holiday on a gravity-mapping mission.
More than 100 missions have been flung to Earth's nearest neighbor since the dawn of the Space Age including NASA's six Apollo moon landings that put 12 astronauts on the surface.
The loss of Ebb and Flow comes on the same month as the 40th launch anniversary of Apollo 17, the last manned mission to the moon.
Ebb and Flow focused exclusively on measuring the moon's lumpy gravity field in a bid to learn more about its interior and early history. After flying in formation for months, they produced the most detailed gravity maps of any body in the solar system.
Secrets long held by the moon are spilling out. Ebb and Flow discovered that the lunar crust is much thinner than scientists had imagined. And it was severely battered by asteroids and comets in the early years of the solar system - more than previously realized.
Data so far also appeared to quash the theory that Earth once had two moons that collided and melded into the one we see today.
Besides a scientific return, the mission allowed students to take their own pictures of craters and other lunar features as part of collaboration with a science education company founded by Ride, who died in July of pancreatic cancer at age 61. About 3,600 classrooms around the world participated, sending back 114,000 photos.
Scientists expect to sift through data and images from the $487 million mission for years.
Obtaining precise gravity calculations required the twins to circle low over the moon, which consumes a lot of fuel. During the primary mission, they flew about 35 miles above the lunar surface. After getting bonus data-collecting time, they lowered their altitude to 14 miles above the surface.
With their fuel tanks almost on empty, NASA devised a controlled crash to avoid contacting any of the treasured sites on the moon. Mission controllers at the NASA Jet Propulsion Laboratory applauded when they lost signal, one of the rare celebrations of a spacecraft's demise.
Mission chief scientist Maria Zuber approached Ride's family about a month ago about naming the impact site. Zuber said she will also petition the International Astronomical Union to name mountain after the late astronaut as well.
"We looked very hard to find a very prominent feature on the near side of the moon that didn't have a name," said Zuber of the Massachusetts Institute of Technology.