The long-held theory that the “Man in the Moon” craters on the moon’s surface were created by asteroids is now under investigation. Many scientists believe the craters may have come from a drastically different source — from within.
CNET reports that new NASA data released this week supports the theory that magma from within the moon itself, not an asteroid strike, created that famous face-like craters. Scientists know the face-like basin as the Procellarum region which stretches nearly 1,800 miles in diameter.
What tipped scientists off in the new theory? The rims of the basin tell the story. Researchers from the Massachusetts Institute of Technology, Colorado School of Mines and other institutions used gravity data from NASA’s GRAIL probes that orbited the moon in 2012 to create a map of the Procellarum region that showed the rims of the basin are actually more angular than circular or elliptical, as one would expect from an asteroid impact. Jim Head, a Professor of Geological Sciences at Brown University, explains what the rim of the basin tells us.
“Instead of a central circular gravity anomaly like all other impact basins, at Procellarum we see these linear features forming this huge rectangle. This shape argues strongly for an internal origin and suggests internal forces.”
The internal forces that created the feature are still under debate. However, the going theory is that a plume of magma rose to the surface, then cooled and contracted, creating formations that could easily be misidentified as impact craters. However, it is currently unknown what caused the plume to rise. Could an asteroid impact still come into play at some point in creating the massive basins?
MIT professor Maria Zuber doesn’t think an asteroid is a likely candidate, but rather radioactive decay of internal elements.
“It could be due to radioactive decay of heat-producing elements in the deep interior. Or, conceivably, a very early large impact triggered the plume. But in the latter case, all evidence for such an impact has been completely erased. People who thought that all this volcanism was related to a gigantic impact need to go back and think some more about that.”
Even prior to the GRAIL mission, there was debate in the science community over how the basins came about. The report notes that the familiar face of the Moon’s near side is dominated by the lunar maria, the dark patches etched across the surface. Most of the large circular features — like Mare Serenitatis (Sea of Serenity) and Mare Imbrium (Sea of Rains) — have been shown to be impact basins that later filled with volcanic lava, which eventually cooled to form the dark basalts. Samples gathered during the Apollo missions, and data gathered by subsequent unmanned missions, helped to confirm that idea.
But the origin of Oceanus Procellarum remained up in the air, largely because it simply doesn’t look like the known basins. It is shaped a bit like a horseshoe, while the other basins are round. Procellarum also lacks surrounding mountains and radial grooves scoured by impact ejecta, both telltale signs of an impact basin.
Still, the idea that Procellarum was indeed formed by an impact surfaced in the mid-1970s. Proponents of the impact theory argued that Procellarum looked different simply because it was much older than the other basins. Because of its age, the telltale mountains and grooves had been eroded away and debris had partially filled the basin’s midsection, giving it the horseshoe shape. However, the new data suggests that there were more differences than originally thought making an impact basin less likely.
This isn’t the first new piece of research to make waves. A new “alien” molecule recently discovered may also hold hints to the origin of life.
How do you think the asteroid-impact theory camp respond to the new claims over the moon’s origin?