This artist rendering released by NASA shows the twin spacecraft Ebb and Flow orbiting the moon. The duo found evidence that the moon’s interior is more battered than previously thought and the crust is thinner than expected.
LOS ANGELES—After nearly a year circling the moon, NASA’s Ebb and Flow will meet their demise when they crash — on purpose — into the lunar surface.
Just don’t expect to see celestial fireworks. The washing-machine-sized spacecraft, which will make impact on Dec. 17 near the moon’s north pole, won’t carve a gaping crater or kick up a lot of debris. And it’ll be dark when it happens.
“We are not expecting a big flash or a big explosion” that will be visible from Earth, said mission chief scientist Maria Zuber of the Massachusetts Institute of Technology.
Still, it’ll mark a violent end to a successful mission that has produced the most high-resolution gravity maps of Earth’s closest neighbour. On Friday, engineers will turn off the science instruments in preparation for Monday’s finale.
Previous unmanned trips to the moon have studied its lumpy gravitational field, but Ebb and Flow are the first ones dedicated to this goal. Since entering orbit over New Year’s weekend, the formation-flying spacecraft have peered past the craggy surface into the interior.
Initially, the spacecraft flew about 55 kilometres above the surface and later dropped down to about 20 kilometres. Roughly an hour before Monday’s impact, they will fire their engines until they run out of fuel and slam at more than 6,100 km/h into a predetermined target — a mountain near the north pole that’s far away from the Apollo landing sites.
Ebb will hit first, followed by Flow 20 seconds later. Though the drama won’t be visible from Earth, the Lunar Reconnaissance Orbiter will fly over the crash site afterward and attempt to spot them.
The last time NASA aimed at the moon was in 2009. The world watched through telescopes and over the Internet as a spacecraft and its booster rocket smashed into a permanently shadowed crater — a one-two punch that fizzled when spectators saw little more than a fuzzy white flash.
The mission’s end will also mark the close of a student campaign that used cameras aboard the spacecraft to image lunar targets, including on the moon’s far side. The MoonKAM project was spearheaded by a science education company founded by Sally Ride, the first American woman in space. Ride died of pancreatic cancer in July at age 61.
Even after Ebb and Flow complete their mission, scientists will continue to pore over the bounty of data they collected.
Among their findings so far: The moon is more beat up than previously imagined. The crust is much thinner than thought. And there’s no evidence that Earth once had two moons that collided to form the one we see in the night sky.