Wednesday, July 09, 2008

Water in Moon's Interior













Two news stories that talk about the water and the moon.


New study finds water in moon rocks

BEIJING, July 10 (Xinhuanet) --

U.S. researchers have found water in rocks from the moon -- prompting new questions about its origin, said a study published in Thursday's British weekly journal Nature.


The discovery was made by analysing small glass beads from lunar sand scooped up by Apollo mission astronauts nearly 40 years ago. They used a new method of analyzing elements in the lunar sand samples to show strong evidence of water, dating back 3 billion years.


The standard "giant impact" theory for the formation of the moon assumes that a huge body crashed into the early Earth, sending massive amounts of molten magma into orbit. This disc of magma gradually coalesced and cooled into the moon as it is today.

But since the moon is too small to maintain an atmosphere, any volatile gases or liquids, such as water, were thought to have bubbled away and escaped into space.

Now a team at Brown University, Rhode Island, has thrown this theory into doubt by finding water in the titanium glass beads that are scattered all over the lunar surface. These are the result of huge lunar volcanic eruptions that occurred billions of years ago.


Importantly, the beads are made from material that originates from deep within the moon -- avoiding any chance that the water could have come from external sources such as comets hitting the surface.


Using high precision secondary ion mass spectrometry (SIMS), the team was surprised to discover that the beads contain around 45 parts per million of water.


By modelling the dynamics of the volcanic eruption and rate of cooling, researchers calculated that approximately 95 percent of any water would have been lost during volcanic activity that brought the beads to the surface.

This leads to an estimate that lava deep within the moon contains water at up to 745 parts per million -- similar to that in Earth's upper mantle.


"Our model is not perfect - so although we know there is water there, we cannot be sure exactly how much," said Alberto Saal, lead author on the research. Even so, Saal added, the presence of water should definitely be considered in future models of the moon's formation.

"This is a surprising and important result," said David Stevenson, an expert on the evolution of planets at the California Institute of Technology. "Water lowers the melting point of rocks, so it could change the evolution of a body such as the moon."

"But one important thing to note is that the moon is probably heterogeneous," Stevenson added. "It is possible that during a giant impact some areas of water could have become trapped. The discovery of water in one place doesn't necessarily mean the rest of the moon is the same."

Here is the link to the original story:
Moon



Here is the second story


U.S. scientists find evidence of water in Moon's interior

WASHINGTON, July 9 (Xinhua) --


A team of U.S. scientists have for the first time discovered evidence of water that came from deep within the Moon, a revelation that strongly suggests water has been a part of the Moon since its early existence -- and perhaps ever since it was created by a cataclysmic collision between the early Earth and a Mars-sized object about 4.5 billion years ago.

In a paper published in the July 10 issue of the journal Nature, the team, led by Alberto Saal from Brown University, believes that the water was contained in magmas erupted from fire fountains onto the surface of the Moon more than 3 billion years ago.


About 95 percent of the water vapor from the magma was lost to space during this eruptive "degassing," the team estimates. But traces of water vapor may have drifted toward the cold poles of the Moon, where they may remain as ice in permanently shadowed craters.


NASA plans to send its Lunar Reconnaissance Orbiter later this year to search for evidence of water ice at the Moon's south pole. If water is found, the researchers may have figured out the origin.


The water clue came from lunar volcanic glasses, pebble-like beads collected and returned to Earth by NASA's Apollo missions in the late 1960s and early 1970s.

In the decades since, scientists have sought to determine the content and origin of a class of chemical elements known as volatiles in the multicolored glasses. In particular, they searched the glasses for signs of water. But such evidence had remained elusive, consistent with the general consensus that the Moon is dry.

Now, that evidence has been found. Based on their observations that nearly all the water in the lunar magma was lost to space during the eruptions, the researchers calculated that the pre-eruption magma may have contained water up to 750 parts per million -- similar to the water content of primitive magmas that erupted on the Earth's seafloor at midocean ridges.

"This suggests the very intriguing possibility that the Moon's interior might have contained just as much water as the Earth's depleted upper mantle," said Erik Hauri, participating researcher from the Carnegie Institution for Science.


Hauri used secondary mass ion spectrometry, a technique that measures the elemental composition of solid materials, to detect the minute amounts of water in the samples. "We developed a way to detect as little as five parts per million of water," Hauri said. "We were really surprised to find a whole lot more in these tiny glass beads, up to 46 parts per million."


The team then confirmed through a series of tests that hydrogen had been present all along, and the samples had not been infused by hydrogen-rich solar winds or tainted by other volatiles. "This confirms that water comes from deep within the mantle of the Moon," Saal said. "It has nothing to do with secondary processes, such as contamination or solar wind."


The researchers this summer will study volcanic glasses gathered from other Apollo missions for evidence of water.


Here is the link to the original story:
Water

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