Moon's interior water casts doubt on formation theory
11 June BBC
An analysis of sediments brought back by the Apollo 17 mission has
shown that the Moon's interior holds far more water than previously
The analysis, reported in Science, has looked at pockets of volcanic
material locked within tiny glass beads.
It found 100 times more water in the beads than has been measured
before, and suggests that the Moon once held a Caribbean Sea-sized
volume of water.
The find also casts doubt on aspects of theories of how the Moon
A series of studies in recent years has only served to increase the
amount of water thought to be on the Moon.
The predominant theory holds that much of the water seen on the lunar
surface arrived via impacts by icy comets or watery meteorites.
But this recent find is shedding light on how much water is contained
in the Moon's interior, which in turn gives hints as to how - and from
what - it formed.
In 2008, a team of researchers from the Carnegie Institution and
Brown and Case Western Reserve universities analysed the water content
found in samples of lunar magma returned by Apollo missions.
They wrote in a Nature paper that the samples contained about 10
times more water than they expected.
However, the magma they studied had formed in "fire fountain"
volcanic events, much like those seen in locations on Earth such as
Hawaii, which would have boiled off much of the water that they
Now the same team has found a number of geological "time capsules"
among the beads. "What we've done now is find samples of magma that are
present as 'inclusions' that are trapped inside solid crystals called
olivine," explained Erik Hauri, a geochemist from the Carnegie
Institution and lead author of the new research.
"Because this magma is trapped inside a crystal, during an eruption
it can't lose its water, so these melt inclusions preserve the original
water content of the magma," he told BBC News.
The team found that those lockets of lunar magma contained some 100
times as much water as the previous samples - meaning that the lunar
interior once held as much water as the layer of the Earth lying just
below the crust.
'Not consistent' As with the 2008 study, the find adds even more
confusion to theories of how the Moon formed. It is widely thought that
a Mars-sized object slammed into the Earth just as it was forming,
throwing out a disc of fragmented, molten material that eventually
coalesced into the Moon.
But in that scenario, the extreme temperatures generated by the
impact would have simply boiled off the water, and the moon should have
started out relatively dry.
While there is a great deal of evidence to support the theory, both
in terms of computer models of planetary formation and of the comparable
amounts of various elements found both here and on the Moon, Dr Hauri
said something just doesn't add up. "These things are not consistent
with the amount of water that we find," he said.
"I think in its very basic form, the [impact theory] idea is probably
still correct, but there's something fundamental about the physics of
the process that we don't understand."
Marlborough Mound: 'Merlin's burial place' built in 2400 BC 11 June
A Wiltshire mound where the legendary wizard Merlin was purported to
be buried has been found to date back to 2400 BC.
Radiocarbon dating tests were carried out on charcoal samples taken
from Marlborough Mound, which lies in Marlborough College's grounds.
The 19m (62ft) high mound had previously mystified historians. Some
believed it dated back to about 600 AD.
English Heritage said: "This is a very exciting time for British
prehistory." Dig leader Jim Leary said: "This is an astonishing