[meteorite-list] Why does the Moon look like this? Here it is in black and white ...

From: Gary K. Foote <gary_at_meteoritecentral.com>
Date: Thu, 01 Feb 2007 19:06:35 -0500
Message-ID: <45C23A3B.9307.7BAA69_at_localhost>

http://thescotsman.scotsman.com/index.cfm?id=166052007

Why does the Moon look like this? Here it is in black and white ...

EBEN HARRELL
 (eharrell at scotsman.com)

SCIENTISTS in Edinburgh have recreated Moon rock in a laboratory and simulated the
conditions of an asteroid explosion to learn why the lunar body has its distinctive black
and white colouration.

The Moon was formed 4.5 billion years ago after the Earth collided with a massive comet
and a large chunk of the debris was trapped in the earth's gravitational pull.

But the collision released a huge amount of energy, in the form of heat, which turned
much of the Moon's surface into a lunar ocean of magma, or lava. The lava then cooled and
solidified. To investigate the effect this cooling had on the Moon's surface, geologists
at Edinburgh University created artificial pieces of Moon rock based on the chemical
compositions of samples brought back from the Apollo space missions. They then used a
special furnace to heat the artificial rock to 1,500C, turning it to magma, and then
watched it cool.

White crystals were the first to form in the magma, floating on top of the black liquid,
suggesting that during its original formation, the Moon was covered by a perfect white
sheen.

But the centre of the scientists' sample - and the Moon - was black.

This all but proves the long-held theory that some 2.5 billion years ago, an asteroid
shower must have hit the Moon, rupturing its white exterior and causing volcanic
explosions of black lava. The lava - dark in colour because of its high concentration of
iron - was slowly pulled by the Moon's weak gravity into valleys, exposing dark craters
and white "lunar highlands".

This is why the Moon is white and black.

Dr Stephan Klemme, the lead researcher, said: "When you look at rocks from the Moon and
from the Earth, they are very similar. The black rock on Arthur's Seat [in Edinburgh],
for example, is not much different from black Moon rock. However, there are crucial
differences that have baffled scientists.

"Our experiments have shown that the minerals creating the white rock - seen in the lunar
highlands - would have crystallised first, whereas the dark and heavy iron-rich minerals
would have sunk in the magma oceans, creating darker rock that would have been buried
deep inside the Moon.

"The reason that the darker rocks are now visible on the surface of the Moon is proof of
a later period of intensive meteorite showers. The iron-rich minerals that were deep
inside the Moon proved to be especially high in hafnium and low in tungsten, and would
have erupted to the surface as molten rock, filling the valleys on the Moon and leaving a
darker shade we observe today."

Dr Klemme, of the university's school of geosciences, said the research was carried out
in Edinburgh because of a specialised furnace that allowed scientists to not only heat
the Moon rock, but do so in atmospheric conditions that mimicked the low-oxygen
conditions found on the lunar surface.

The research comes during renewed interest in manned exploration of Earth's only
satellite. Last month, NASA, the US space agency, outlined plans for a permanent base on
the Moon as part of preparation for a voyage to Mars. Construction of the base is
scheduled to take about five years, with the first preliminary missions beginning by
2020.

The latest findings serve as another confirmation of the giant-impact hypothesis for the
formation of the Earth-Moon system. In this theory, the impact of a Mars-sized body,
which has been referred to as Theia or Orpheus, into the proto-Earth is thought to have
put enough material into the planet's orbit to create the Moon. Computer simulations can
account for the angular momentum of the Earth-Moon system, as well as the small size of
the lunar core.
Received on Thu 01 Feb 2007 07:06:35 PM PST