Under the biggest crater in our solar system — the Moon’s South Pole-Aitken basin — a mysterious mass of material has been found and may contain metal from the asteroid that crashed into the Moon and created the crater, according to a research by Baylor University.
“Imagine taking a pile of metal five times larger than the Big Island of Hawaii and burying it underground. That’s roughly how much unexpected mass we detected,” said Peter James, lead author of the study and assistant professor of planetary geophysics in Baylors College of Arts & Sciences.
The crater itself is oval, as large as 2,000 kilometers — about the range between Waco, Texas, and Washington, D.C .— and a few miles profound. It can’t be seen from Earth despite its size because it’s on the far side of the Moon.
The study is published in the journal Geophysical Research Letters.
Researchers analyzed information from spacecraft used for the National Aeronautics and Space Administration (NASA) Gravity Recovery and Interior Laboratory (GRAIL) mission to assess subtle changes in gravity intensity around the Moon.
“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. “One of the explanations of this extra mass is that the metal from the asteroid that formed this crater is still embedded in the Moon’s mantle.”
The dense mass—”whatever it is, wherever it comes from “— weighs more than half a mile down the basin ground, he said. Computer simulations of big asteroid impacts indicate that an asteroid’s iron-nickel core may be distributed during an effect under the correct circumstances into the upper mantle (the layer between the Moon’s crust and core).
Another chance is that the big mass could be a thick oxide concentration connected with the last phase of solidification of the lunar magma ocean.