Researchers have discovered something massive lurking underneath the far side of the moon: a mysterious blob with the mass akin to a pile of metal.
The structure, described in a recent study published in Geophysical Research Letters, sits at least three hundred kilometres beneath the main crater on the moon, the South Pole-Aitken basin—a colossal crater punched into the lunar landscape billions of years ago.
The team discovered the anomalous blob by combining data from NASA’s Gravity Recovery and Interior Laboratory, (GRAIL), mission with topography from the Lunar Reconnaissance Orbiter. This data helped them refine past calculations for the thickness of the crater’s crust and the density of the mantle, revealing the odd underground excess of mass.
The blob is likely related to the crater’s formation, and it may be the remnants of an ancient impactor’s metal core, says study coauthor Peter James of Baylor University. While the excess mass isn’t immediately obvious from the surface, it does seem to be having quite an effect, dragging down the lunar landscape in a curious ovoid depression that sits around two kilometres lower than the surrounding crater floor, a feature known as the central depression.
The only way to know for sure, though, is to send a lander or people to further study the basin.
That might be a real possibility: Just two months out from the 50th anniversary of the Apollo 11 moon landing, NASA announced this past May that it is planning to return to the moon in 2024.
The research relied on two key missions in NASA’s moon-exploration portfolio. The GRAIL mission included two spacecraft, which spent more than a year orbiting the moon, with each spacecraft using the other to map the gravitational tug of the moon. The Lunar Reconnaissance Orbiter has spent nearly 10 years at work and has made billions of measurements of the precise height of the moon’s surface.
