'Imagine taking a pile of metal five times larger than the big Island of Hawaii and burying it underground, ' said lead author Peter B. James, from Baylor University's College of Arts & Sciences.
Researchers studied data obtained from the spacecrafts used for NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission.
"The dense mass - whatever it is, wherever it came from - is weighing the basin floor downward by more than half a mile".
A mysterious mass of material has been spotted by researchers under the surface of the Moon.
Deep below the moon's South Pole-Aitken basin (the largest preserved impact crater anywhere in the solar system), researchers have detected a gargantuan "anomaly" of heavy metal lodged in the mantle that is apparently altering the moon's gravitational field.
This false-color graphic shows the topography of the far side of the Moon. At about 2,000 km wide the South Pole-Aitken basin is the largest crater known to scientists, with the newly-discovered mass underneath it being large enough to affect the moon's gravity. According to new research, this mass anomaly may contain metal from a massive asteroid that crashed into the Moon and formed the crater. Larger variations helped tease out information about the moon's core, and subtler ones revealed unseen mineral deposits, asteroid impact sites, and subsurface features.
"When we combined that with lunar topography data from the Lunar Reconnaissance Orbiter, we discovered the unexpectedly large amount of mass hundreds of miles underneath the South Pole-Aitken basin", he said. All of that metal, and basically the entire area surrounding the mass and the crater, could tell them a lot about how the asteroid impact happened and what the solar system was like when it did.
The team ran complicated computer simulations of large asteroid impacts which suggested that - under the right conditions - an asteroid which had an iron-nickel core could have dispersed into the moon's upper mantle during an impact.
While there have been many craters that have formed due to asteroid impacts over time, none are as well-preserved as the Aitken basin, which is thought to have been formed four billion years ago. The Lunar Reconnaissance Orbiter has spent almost 10 years at work and has made billions of measurements of the precise height of the moon's surface.
The colliding body is sometimes called Theia, named after the mythical Greek Titan who was the mother of Selene, the goddess of the Moon.
Several different theories have emerged over the years to explain the similar fingerprints of Earth and the moon. Things like when researchers successfully brought some frozen 40,000-year-old worms back to life last year or when Harvard's astronomy chair theorised that 'Oumuamua, the first interstellar object ever documented passing through our solar system, could be a solar-sail-powered alien probe.
A third possibility is that the moon formed from Earthen materials, rather than from Theia, although this would have been a very unusual type of impact.