Researchers are using data from the "lunar-orbiting twins of NASA's Gravity Recovery and Interior Laboratory (GRAIL)" to get a closer look at the moon's iconic craters, and have run into some surprises.
"Since time immemorial, humanity has looked up and wondered what made the man in the moon," Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology in Cambridge said in NASA Jet Propulsion Laboratory news release. "We know the dark splotches are large, lava-filled, impact basins that were created by asteroid impacts about four billion years ago. GRAIL data indicate that both the near side and the far side of the moon were bombarded by similarly large impactors, but they reacted to them much differently."
There is "lack of consensus" on the craters' size because many of the craters on the near facing side of the moon are filled to the brim with lava, making it hard to tell.
The GRAIL mission aimed to redefine the dimensions of these craters by measuring the "internal structure of the moon in unprecedented detail for nine months in 2012."
The data revealed more large impact basins on the near-side hemisphere (the moon's face) than the far side. This finding was unusual because the entire moon is believed to have received relatively equal bombardment from outside space objects.
Past research has shown the near-hemisphere of the moon is much hotter than the far-side and has a more abundant presence of the heat-producing elements uranium and thorium.
"Impact simulations indicate that impacts into a hot, thin crust representative of the early moon's near-side hemisphere would have produced basins with as much as twice the diameter as similar impacts into cooler crust, which is indicative of early conditions on the moon's far-side hemisphere," lead author Katarina Miljkovic of the Institut de Physique du Globe de Paris, said.
The GRAIL study has also helped researchers gain insight into the "late heavy bombardment," which was a proposed spike in asteroid impact on the moon four billion years ago.
"The late heavy bombardment is based largely on the ages of large near-side impact basins that are either within, or adjacent to the dark, lava-filled basins, or lunar maria, named Oceanus Procellarum and Mare Imbrium. However, the special composition of the material on and below the surface of the near side implies that the temperatures beneath this region were not representative of the moon as a whole at the time of the late heavy bombardment," the news release reported.
The difference in temperature profiles would have caused researchers to overestimate the severity of the
