Twin NASA spacecraft built in Colorado crashed into the surface of the moon Monday at 3:29 p.m. MST and about 1.9 miles apart after completing a relatively brief but successful mission.

"The probes' mission objective was to obtain a gravity map of the moon in unprecedented detail," said Cavan Cuddy, Spacecraft Team system lead with Lockheed Martin in Waterton Canyon. "The mission has produced the highest resolution of any planetary body to date."

Lockheed Martin workers in Colorado designed, built and operated the two craft, named Ebb and Flow, under NASA's $500 million Gravity Recovery and Interior Laboratory or GRAIL program.

A key finding the probes made is that the moon's crust is not as thick as originally thought, and comparable to the earth's crust. That supports models that the moon originated out of an impact with Earth rather than being captured by it, said Mark Wieczorek, GRAIL co-investigator, in a statement.

The two craft, about the size of washing machines, traveled at a synchronized distance from each other with equipment that could measure minute fluctuations resulting when they encountered changes in the gravitational pull.

NASA launched the craft together in September 2011, and they began mapping the moon at the start of the year from an altitude of 34 miles.


By May, they had completed their initial mission with enough fuel to start a second round, which they did at the end of August at a lower altitude of 14 miles. The lower orbit required weekly adjustments to keep the craft synchronized, Cuddy said.

Eventually, the fuel ran out. Rather than have the probes crash uncontrolled at an unknown spot, the Lockheed Martin team brought them down near the Goldschmidt crater, far removed from historic areas like the Apollo landing sites.

The twin spacecraft, named Ebb and Flow, are shown being assembled in Colorado under NASA&#8217;s Gravity Recovery and Interior Laboratory program.
The twin spacecraft, named Ebb and Flow, are shown being assembled in Colorado under NASA's Gravity Recovery and Interior Laboratory program. (Provided by Lockheed Martin)

"It is extremely rare to have an end of the mission like this," Cuddy said.

Ebb and Flow, built at the foot of the Rocky Mountains, met their demise traveling an estimated 3,760 mph on another rocky mountain slope, one near the moon's north pole.

The area where the spacecraft made impact was renamed after astronaut Sally Ride, who in 1983 became the first American woman to enter low-earth orbit. Ride died in July of pancreatic cancer.

Elementary school students in Montana won a contest to name the probes, which contained four cameras each. Students and enthusiasts could take pictures of the lunar surface as part of a public outreach program by NASA.

Cuddy said about 150,000 images of the moon were taken.

Aldo Svaldi: 303-954-1410, or

34 miles

The altitude at which the twin craft, built in Colorado and launched in September 2011, mapped the moon.

14 miles

The altitude the craft mapped the moon in their second round.


The miles per hour that the craft were traveling when they crashed near the moon's north pole on Monday.


The number of images taken by the four cameras mounted to each probe.