Lava surprise found in the Moon
2012-02-20 14:05
Cape Town - Far from being a dead satellite, scientists have found strong evidence of hot molten lava deep within the Moon's interior.
On Earth, the pressure of lava produces volcanoes, but on the Moon, the molten interior could be so dense that it is simply too heavy to rise to the surface, the team led by Mirjam van Kan Parker and Wim van Westrenen from VU University Amsterdam reported.
The scientists produced microscopic copies of Moon rock collected by the Apollo missions and melted them at the extremely high pressures and temperatures found inside the Moon.
Researcher Renee Weber and her colleagues claim that the deepest parts of the lunar mantle, bordering on the small metallic core, are partially molten, by up to 30%.
On Earth, these bodies of magma would move toward the surface and create volcanoes, but the surface of the Moon is quiet by comparison.
Bubble
The driving force for vertical movement of magma is the density difference between the magma and the surrounding solid material, making the liquid magma move slowly upwards like a bubble. The lighter the liquid magma is, the more violent the upward movement will be.
A study made public in 2011 found a set of dormant volcanoes on the far side of the moon.
Data and photos from Nasa's Lunar Reconnaissance Orbiter revealed the presence of silicate volcanoes, not the more common basaltic volcanoes that litter the moon's surface, the researchers said.
To determine the density of the magma, the scientists at the European Synchrotron Radiation Facility (ESRF) in Grenoble used a powerful synchrotron X-ray beam.
"We had to use the most brilliant X-ray beam in the world for this experiment because the magma sample is so tiny and confined in a massive, highly absorbing container. Without a bright beam of X-rays, you cannot measure these density variations," said Mohamed Mezouar from the ESRF.
The scientists concluded that large vertical movements must have occurred early in the history of the Moon, during which titanium-rich rocks descended from near the surface all the way to the core-mantle boundary.
The cooling action resulted in highly enriched titanium accumulating.
"After descending, magma formed from these near-surface rocks, very rich in titanium, and accumulated at the bottom of the mantle - a bit like an upside-down volcano," said Van Westrenen.
