'Man in the Moon' Created by Mega Volcano

Whenever you look up at the near side of the moon, you see a face looking back at you. This is the “Man in the Moon” and it has inspired many questions about how it could have formed.

There has been some debate as to how this vast feature — called Oceanus Procellarum, which measures around 1,800 miles wide — was created. But after using gravity data from NASA’s twin GRAIL spacecraft, researchers have found compelling evidence that it was formed in the wake of a mega volcanic eruption and not the location of a massive asteroid strike.

The key issue with understanding how the Procellarum basin could have formed is that the moon is pockmarked with billions of years worth of impact craters. These craters have excavated the lunar surface, wiping out features that could have pointed to Procellarum’s origins.

In new research published today in the journal Nature, geophysicist Maria Zuber, of Massachusetts Institute of Technology (MIT), used data from GRAIL to find the basin is actually of a polygonal shape, rather than a smooth circle (or oval) that is commonly associated with impact craters. Its edges are composed of straight edges linked at 120 degree angles.

GRAIL — an acronym for Gravity Recovery and Interior Laboratory — consisted of two spacecraft, one chasing the other, above the moon’s surface. Their mission started in January 2012 and ended, spectacularly, in the following December when they were deliberately steered to crash into the moon’s terrain.

During their mission, as one spacecraft orbited over a region of dense rock, the gravitational field of the moon would slightly increase, speeding the leading probe up. Likewise, when traveling over a less dense region, the leading spacecraft would slow down. As a result, the distance between the two spacecraft would vary, providing NASA with very precise data about the distribution of lunar gravity and, therefore, a density map of the hidden rock beneath the surface.

After discovering the density of rock represented a massive lava flow rather than a massive asteroid strike, Zuber’s team set out to model how such a huge quantity of lava could have spilled onto the surface, creating the basin we see today.

By simulating volcanic intrusions below the surface and interpreting how that gravitational signal may have been recorded by GRAIL, the researchers found that GRAIL recorded a similar rock density structure below Procellarum. Therefore, shortly after the moon had formed and cooled, a huge plume of molten rock was pushed up from the moon’s interior. The steep temperature difference between the basin and the surrounding rock caused the surface to contract, fracturing the lunar crust, creating routes for molten material to escape to the surface.

Read more at Discovery News