NASA’s twin GRAIL satellites, currently maneuvering into position for an innovative moon mapping mission, have new names: Ebb and Flow.

That might sound a bit strange, but it’s actually an apt description of how the two probes work.

To map the moon’s gravity, which will tell scientists a great deal about what’s inside, the spacecraft will follow one another in circles over the lunar poles. Regions that are denser with matter will cause first one satellite and then the other to momentarily speed up.

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By constantly measuring the distance between the two probes, scientists can generate maps of the moon’s gravity and create models of its interior, a key piece of missing data despite more than 100 previous missions to the moon.

Naming rights went to a group of fourth-graders from Bozeman, Mont., who won a national essay competition with their entry “Ebb and Flow.”

“The students of Nina DiMauro’s class at the Emily Dickinson Elementary School have really hit the nail on the head,” Maria Zuber, lead scientist for NASA’s Gravity Recovery And Interior Laboratory (GRAIL) mission, said in a press release.

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“We were really impressed that the students drew their inspiration by researching GRAIL and its goal of measuring gravity. ‘Ebb and Flow’ truly capture the spirit and excitement of our mission,” she said.

NASA and its educational partner, Sally Ride Science, received 890 entries from students across the United States and abroad.

For their prize, the Dickinson Elementary School students will get to choose the first picture to be taken with the satellite’s camera, another educational outreach program called MoonKAM (short for Moon Knowledge Acquired by Middle school students).

Nearly 2,000 schools have registered to participate in MoonKAM.

Launched in September 2011, Ebb and Flow arrived at the moon on Dec. 31 and Jan. 1 respectively. They are in the process of maneuvering into near-polar, circular orbits about 34 miles above the lunar surface.

Image: The twin GRAIL probes communicating with Earth and each other. Credit: NASA