"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", James said in the statement. To me, this story about scientists discovering a massive metallic mass underneath a crater on the Moon has exactly the same vibes. "That's roughly how much unexpected mass we detected", said lead author Peter B. James, Ph.D., assistant professor of planetary geophysics in Baylor's College of Arts & Sciences.
Unfortunately the crater - and the mysterious substance below - aren't visible to mere earthbound humans, since they're on, literally, the far side of the moon.
This false-color image shows the South Pole-Aitken (SPA) basin region in a topographical map.
The South Pole-Aitken basin on the far side of the moon is said to be the largest crater in the solar system and extends several miles deep.
Researchers studied data obtained from the spacecrafts used for NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission. According to the published study, "Plausible sources for this anomaly include metal from the core of a differentiated impactor or oxides from the last stage of magma ocean crystallization", which hypothesizes the moon's surface was once a molten liquid ocean of magma. Beneath this basin lies a odd anomaly-an excess of mass extending at least 300 kilometers down, more than 10 times the depth of the Earth's crust. This large mass may be a remnant of the asteroid that crashed into the Moon and formed the crater - which would also mean that it could be made up nearly entirely out of metal.
This mass, the researchers believe, is weighing the floor of the basin downward by more than 800 metres, around 10 percent of its total depth, explaining a depression in the bottom of the basin previously attributed to contraction. The team of researchers ran computer simulations that show the iron-nickel core of an asteroid could have been placed into the upper mantle of the Moon following impact. Perhaps some process caused certain materials to concentrate beneath the basin as the lunar mantle cooled.
"The South Pole-Aitken basin - thought to have been created about 4 billion years ago - is the largest preserved crater in the Solar System", Dr. James said. Other larger impacts may have taken place, including on Earth, there is no lasting trace of them.
Finding out how the South Pole-Aitken basin formed is important to understanding the history of the moon and its evolution.