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Just a few weeks before their one year anniversary in space, two twin probes capturing what the inside of the moon looks like, will smash themselves into a lunar mountain while the world (or, at least, the Internet) watches.

NASA will livestream the planned crash today at 5pm Eastern Time (2pm Pacific Time).

The probes named Ebb and Flow have been circling the moon for a year, mapping the internal structure of the moon. Researchers says it is the “highest-resolution gravity field map of any celestial body.” To get this, Ebb and Flow had to fly closer to the moon’s surface, as Ars Technica notes, and do not have enough fuel to leave its gravitational pull. NASA researchers decided the safest move was to smash them into the moon’s surface as opposed to letting them fly aimlessly as this might cause one of the probes to crash into a historical site, such as the Apollo landing site.

Before they go down, however, Ebb and Flow will conduct one last test, burning off all remaining fuel. This will help researchers determine how much fuel to use in future missions.

“Our lunar twins may be in the twilight of their operational lives, but one thing is for sure, they are going down swinging,” said GRAIL project manager David Lehman of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Even during the last half of their last orbit, we are going to do an engineering experiment that could help future missions operate more efficiently.”

Ebb will head to the mountain near the Goldschmidt crater first, followed soon thereafter by Flow.

Thumbnail via Shutterstock