The far side of the moon has brought a fresh surprise to scientists when they discovered a rare volcanic hot spot on the mysterious 'other side' of the moon hidden from the earth.

A set of dormant silicate volcanoes were spotted on the far side of the moon, indicating that the moon has been more geologically active than initially thought. Created by the upwelling of silicic magma, the volcanic 'hot spot' is a concentration of the radioactive element thorium, residing between the Compton and Belkovich impact craters. It was first observed in 1998 by a space mission Lunar Prospector's gamma-ray spectrometer.  

The "far side" of the Moon is that part of the Moon which is not visible from Earth, or what is called the lunar hemisphere permanently unseen from Earth. This happens because the Moon's rotation is affected by tidal forces between Earth and the Moon. The latest images obtained by NASA have gone to prove that volcanoes of a rare type had been active on the far side, which resulted in dome-like formations above the surface.  

Recent observations with NASA's Lunar Reconnaissance Orbiter's (LRO) powerful optical cameras allowed scientists to distinguish volcanic features in terrain at the center of the bull's-eye, revealing geological features diagnostic of silicic volcanism, much rarer than the more common basaltic volcanoes which litter the moon's surface, said researchers.

The volcanic province has an irregular depression at its center and at its edge has domes with features that suggest they were formed by the intrusion of high-viscosity silicic lava.

Silicic lava is very unusual, says Bradley Jolliff, of Washington University in St. Louis, who led the team that analyzed the LRO images.

"There are only about a half dozen other features on the Moon that are thought to be silica-rich, because the Moon, unlike the Earth, does not reprocess rock materials in a way that concentrates silica."



This image from NASA's Lunar Reconnaissance Orbiter shows a region on the far side of the moon between the Compton and Belkovich craters. The colored region marks a high amount of the mineral thorium, which is thought to have been deposited by rare silicate volcanoes in the past. (NASA/GSFC/ASU/WUSTL, processing by B. Joliff)



The presence of the volcanic province will lead scientists to reconsider ideas about the moon's volcanic history. 

"To find evidence of this unusual composition located where it is, and appearing to be relatively recent volcanic activity is a fundamentally new result and will make us think again about the Moon's thermal and volcanic evolution," said Jolliff.

These findings are described in the current issue of the journal Nature Geoscience.



Small dome in the Compton-Belkovich region (61.33 °N, 99.68 °E). Evidence indicates a volcanic origin for this and other intriguing features in the region. Incidence angle is 64°, Sun is from the SSW, image is ~510 m across. [NASA/GSFC/Arizona State University].



Geology lecturer Ian Graham from the University of New South Wales said the discovery is highly significant, according to Discovery News. "It's much higher in silicon and potassium than the basaltic volcanism seen elsewhere on the moon" Graham said.

"It's also the first evidence of such young volcanic activity on the lunar surface, meaning the moon was still geologically active just 800 million years ago, rather than 1.2 billion years ago as previously thought." 


"It's been 42 years this month since we first walked on the moon and we're still finding out new things."  

Surprises from the moon aren't exhausted quite yet.