In June 2019, scientists discovered something strange buried 180 miles beneath the lunar surface. While the discovery does sound eerily similar to the beginning of Stanley Kubrick’s film, 2001: A Space Odyssey, scientists have a much more scientific explanation for this particular anomaly. Instead of an alien monolith, scientists think that it is actually an estimated 4.8 quintillion pounds of metal — a deposit formed from leftover shrapnel from an asteroid impact.
“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,” Peter B. James, assistant professor at Baylor University who was involved in the study, said in a statement at the time.
The deposit is underneath the Moon’s largest impact crater, the South Pole-Aitken basin, which itself measures 2,000 kilometers (roughly 1243 miles) across. These kinds of lunar pockmarks are not uncommon for the Moon (as evidenced by its iconic cratered surface), and are better preserved than the Earth’s thanks to the Moon’s lack of erosion, tectonics, or volcanism. If anything dents the moon, the dent is there to stay.
It was discovered when NASA scientists were reviewing information about the Moon’s interior gathered from the GRAIL mission in 2011.
“When we combined [that data] 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.”
Using computer simulations of an asteroid impact, the scientists determined that it would be possible for the iron-nickel core of such an asteroid to be dispersed into the upper lunar mantel (between its core and crust.)
While there isn’t much new information about this anomaly since it’s discovery in the summer, there may be opportunities to learn more about it in years to come as science agencies begin to focus their attention toward the Moon once more.
At the beginning of 2019, the China National Space Administration became the first nation to land a rover, Chang’e-4 in this basin, which is on the Moon’s “dark” side. In 2020, they plan to send a second rover, Chang’e-5, to the same location for sample retrieval and return.
NASA is also aiming to return astronauts to the moon — though not necessarily the far side — by 2024 as part of its Artemis program. These astronauts will be testing out technology and living practices necessary for eventual Martian spaceflights, too.
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