NASA is planning on crashing a pair of lunar probes into the moon next week at the end of a yearlong mission to learn what lies underneath the lunar surface.
The probes are twin Gravity Recovery and Interior Laboratory spacecraft (GRaIL), named Ebb and Flow. They will take their suicidal plunge on Monday into a mountain located near the moon’s north pole, reports The Guardian.
The impacts likely won’t be visible from Earth, partially because of how small the probes are and also because the impacts will take place when the moon’s northern part is dark. They will take place about 20 seconds apart at 5:28 pm EST on Monday.
The two lunar probes are currently flying about seven miles above the moon’s surface and are about the size of a washing machine. They are almost out of gas but have enough make one final steering maneuver before their science instruments are shut down in preparation for Monday’s impact.
Gravity maps made from the first part of the probes’ mission showed that the moon has a much shallower and broken up crust than scientists expected. The fracturing is the result of several asteroid and comet impacts made billions of years ago.
Wired notes that, despite the success of CRaIL, the mission’s project manager, David Lehman, of JPL, stated:
“I’m hoping tonight, a gas station will pull up next to our spacecraft, refuel it, and we can continue on for another six months. The mission is almost over. It’s king of sad for me. I think our team’s done an outstanding job.”
The impact site for the twin probes was chosen in part to avoid historical heritage sites that are associated with the Apollo, Surveyor, Luna, and Lunokhod programs. GRaIL’s principal investigator, Marka Zuber of MIT, explained:
“The impacts are going to occur in the dark, so we will not have live images. We’re not expecting a flash that is visible from Earth. But nonetheless, LRO, which has extremely, extremely sensitive instruments, will attempt to make some observations.”
The twin probes will impact the surface of the moon at about 3,760 miles per hour. The scientists will use the craters left by the probes to study other impacts on the moon’s surface.