GRAIL visualises man in the Moon

The Procellarum, a recess on the western edge of the moon, likely arose from a large plume of magma deep within the moon’s interior rather a massive asteroid strike. New data from NASA’s GRAIL mission has been used to create a high resolution map which revealed a series of linear gravitational anomalies forming a giant rectangle nearly 1,600 miles across running underneath the Procellarum region. These anomalies are the remnants of ancient rifts in the Moon’s crust say the authors in their Nature paper. Between 3 and 4 billion years ago, these rifts provided a vast magma plumbing system that flooded the region with volcanic lava, which solidified to form the dark basalts we see from Earth. “Instead of a central circular gravity anomaly like all other impact basins, at Procellarum we see these linear features forming this huge rectangle,” said Jim Head from Brown University. “This shape argues strongly for an internal origin and suggests internal forces.” The polygonal shape consists of sharp angles that could not have been created by a massive asteroid. Instead, researchers believe the angular outline was produced by tension cracks. The Procellarum – often referred to as the man in the moon – has a high concentration of uranium, thorium and potassium, which all produce heat. Researchers believe these elements may have caused the area to cool and solidify after the rest of the crust, pulling it away from the surrounding crust forming the giant rifts, which magma then flowed into. “We think this is a really good, testable alternative to the impact basin theory,” said Head. “Everything we see suggests that internal forces were critical in the formation of Procellarum.” [caption id="attachment_40114" align="alignright" width="350"] The moon as observed in visible light (left), topography (center, where red is high and blue is low), and the GRAIL gravity gradients (right). The Procellarum region is a broad region of low topography covered in dark mare basalt. The gravity gradients reveal a giant rectangular pattern of structures surrounding the region. Credit:
NASA/Colorado School of Mines/MIT/JPL/Goddard Space Flight Center[/caption] To test this, researchers modelled the region’s gravitational signal if it were to contain volcanic intrusions and the resulting simulation matched the gravity signal recorded by GRAIL, supporting the idea a plume caused the Procellarum. “How such a plume arose remains a mystery,” said Maria Zuber, principal investigator for the GRAIL mission. “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.” Proving the hypothesis may require a new lunar mission involving a long-lived geophysical network to monitor seismic and heat signals from the deep interior. Structure and evolution of the lunar Procellarum region as revealed by GRAIL gravity data Learn more about GRAIL here https://www.youtube.com/watch?v=_hknIsPNsl8