After little over a year in space, NASA's twin GRAIL probes are expected to crash onto the moon's surface only days from Thursday.
According to Reuters, NASA plans to crash its twin Gravity Recovery and Interior Laboratory (GRAIL) spacecraft into a mountain near the north pole of the moon on Monday, Dec. 17.
The site, where they will crash just before 5:30 p.m. EST on Monday, was selected in order to prevent the probes from damaging any iconic moon relics when they crash land.
"They're going to be completely blown apart," GRAIL project manager David Lehman, with NASA's Jet Propulsion Laboratory in Pasadena, California, told reporters on a conference call.
The two GRAIL probes, named Ebb and Flow, launched in September 2011 from a United Launch Alliance Delta II rocket at Cape Canaveral Air Force Station's Complex 17, and arrived at their destination in January. The main objective of the probes was to map lunar gravity between March and May.
As Science News reports, the twin probes discovered that the moon's crust is thinner and more fractured by meteorite impacts than scientists had come to realize. The fractures had been caused by asteroids and comets striking the moon's surface some billions of years past.
"We know that the moon had been bombarded by impacts but what we found is just how broken up and fractured the crust of the moon is," lead scientist Maria Zuber, with the Massachusetts Institute of Technology, told Reuters.
That finding was significant in helping scientists develop theories over one of outer space's biggest questions--what happened to the water that was once on Mars?
"All planetary crusts have been bombarded in a similar way. Earth has...Mars has. With Mars, there's a lot of questions about where did the water that we think was on the surface of Mars go," Zuber said, according to Florida Today. "Well, if a planetary crust is that fractured, these fractures provide a pathway deep inside the planet, and it's very easy to envision now how a possible ocean at its surface could have found its way deep into the crust of a planet."
Another key discovery the probes helped discover was that the amount of aluminum in the crusts of the moon and Earth are nearly equal. This, Zuber said, could mean that the moon was in fact created when a large body from outer space, roughly the size of Mars, collided into Earth.
While the two probes are estimated to be the size of two washing machines, scientists expect that the crash landing of the probes won't make for any dramatic effect, such as explosions.
Still, Lehman said, that the crash would not be safe for anyone to be near.
"It would be like a washing machine coming in and landing on you, and it would be a very bad day for you," Lehman told Florida Today.