Humans have long wondered on the origins of the "Man in the Moon," the craters on the moon that roughly form the shape of the human face.
Old stories suggest that the figure belonged to a man who was banished to the lunar orb for committing a crime, which of course isn't plausible. Earlier scientific theories, on the other hand, propose that the Oceanus Procellarum or the Ocean of Storms, as the feature is also known, was formed by an asteroid impact. Unfortunately, this idea is also marked by loopholes in that the Procellarum, which measures about 1,800 miles in diameter, does not have the features of an impact basin.
Findings of a new study provide proof that volcanic plume has something to do with the lunar feature. For the study, which was described in the journal Nature on October, the researchers used data from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission, which uses high-quality gravitational field mapping of the moon to study its structure.
The researchers identified linear gravitational anomalies that form a giant rectangle about 1,600 miles across that run underneath the Procellarum region and this casted doubts on the asteroid impact theory.
"The discontinuous surface structures that were earlier interpreted as remnants of an impact basin rim are shown in GRAIL data to be a part of this continuous set of border structures in a quasi-rectangular pattern with angular intersections, contrary to the expected circular or elliptical shape of an impact basin," the researchers wrote.
The researchers said that the shape was not likely formed by collision as this would have produced a more circular rim. Instead, the shape may have been the result of geological activity within the crust of the moon.
"Instead of a central circular gravity anomaly like all other impact basins, at Procellarum we see these linear features forming this huge rectangle," said study researcher James Head III, from the Department of Earth, Environmental and Planetary Sciences at Brown University. "This shape argues strongly for an internal origin and suggests internal forces."
The researchers interpreted this series of anomalies as valleys where the moon's crust has been stretched and thinned which were later filled by volcanic lavas more than 3 billion years ago.
"We interpret the gravity anomalies discovered by GRAIL as part of the lunar magma plumbing system -- the conduits that fed lava to the surface during ancient volcanic eruptions," said GRAIL mission principal investigator Maria Zuber.
