[tt] NYT: After 40 Years, Moon Rocks Still in Demand for Research

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After 40 Years, Moon Rocks Still in Demand for Research
http://www.nytimes.com/2008/07/08/science/space/08moon.html

The Keepers of the Moon
By GUY GUGLIOTTA

HOUSTON -- In the lab, the Moon rocks look nondescript -- dark gray
basalt, a whitish mineral called anorthosite and mixtures of the two
with crystals thrown in. Yet nearly 40 years after the Apollo
astronauts brought the first rocks back to Earth, these pieces of
the Moon are still providing scientists with new secrets from
another world.

"We call this one the `genesis' rock, because it was formed close to
the time the Moon solidified about 4.5 billion years ago," said
Carlton C. Allen, pointing to a light-colored stone about the size
and shape of a large artist's eraser, resting inside a glove box
filled with inert nitrogen gas.

"We know the Big Bang happened about 14.5 billion years ago," Mr.
Allen said, "and this rock is a third that old. You will never see a
solid piece of stuff in our solar system that is any older."

Mr. Allen is the astromaterials curator at the Johnson Space Center,
home of the Lunar Sample Laboratory Facility, a secure repository
opened in 1979 to house 842 pounds of Moon rocks and soil collected
by astronauts in six visits.

The rocks on the lunar surface, lying virtually unchanged in a
weatherless vacuum since their formation, offer opportunities to
investigate the origin and evolution of the solar system available
nowhere else, and the study deepens with each new generation of
scientists and scientific instruments.

Each year an independent peer review panel evaluates new research
proposals, and curators mail out about 400 lunar samples to 40 to 50
scientists worldwide. Almost all are less than one gram in size. "We
don't hand them out, we only loan them," Mr. Allen said. "We're not
planning to run out any time soon."

Over the years, the samples have provided uncounted insights into
the nature of our closest celestial neighbor. Because of the
samples, we have learned when the Moon was formed, probably
(although it is still controversial) the result of a planetoid
smashing into the young Earth, throwing a cloud of debris into space
that subsequently came together in a sphere.

The samples have confirmed that asteroid and meteor impacts, not
volcanism, created the vast majority of craters that define the
Moon's topography, while a constant barrage of meteorites,
micrometeorites and radiation melted and pureed the bedrock to
create the blanket of fine-grained soil and dust -- known as
regolith -- that now cloaks the lunar surface.

And knowing the ages of Moon rocks, which can be computed to within
20 million years, has enabled scientists to establish a baseline
that allows them to date geologic features throughout the solar
system. The surface of the Earth, one of the solar system's youngest
topographies, is constantly changing, as it is faulted, folded,
shaped and reshaped by eruptions, earthquakes and erosion. By
contrast, the Moon is as old as it gets.

"It's hard to wrap your mind around a place where nothing ever
happens," Mr. Allen said. "But the Moon is that place."

In recent years the rocks have also helped researchers to answer
practical questions that have emerged since President Bush's 2004
proposal to return to the Moon by 2020 and set up a permanent
outpost. Planners are using the rocks to study the pernicious
effects of regolith on machinery and astronaut health. They are
learning how to extract oxygen and other vital elements from lunar
rocks and soil. And they need to understand how to shield living
spaces from the deadly radiation that eternally pounds the lunar
surface.

The samples -- 2,200 of them -- are kept in nitrogen-filled boxes in
a stainless steel vault on the second floor of the
14,000-square-foot repository, and are transferred to other parts of
the lab in airlocks. Technicians prepare shipments in glove boxes
containing sterile tools and containers.

The samples are numbered and sorted by expedition. All of the Apollo
landings, beginning with Apollo 11's historic mission in 1969 and
ending with Apollo 17 in December 1972, were at equatorial sites,
but terrain differed each time and the samples reflect the
differences. The genesis rock was collected by Apollo 15 astronauts
near Hadley Rille at the border between a lowland "sea," or mare,
and the lunar highlands.

The arrival of the first Moon rocks in 1969 was eagerly anticipated
by scientists. "We had no idea what the Moon was made of," Mr. Allen
recalled, and the first two decades of research focused on basic
questions -- the age and composition of the Moon rocks and the
origin and evolution of the Moon's geology and salient topographical
features.

The early Moon developed as a mostly liquid ball of magma covered
with a thin crust of lighter minerals. The crust became the white
anorthosite, which floated atop the magma to form the lunar
highlands. The basalt erupted later and subsequently solidified in
the lowland marea.

The anorthosite and similar rock types in the highlands and basalt
lavas in the marea are the Moon's basic building blocks. Other rocks
are breccias -- crushed and broken rock fragments, fused by the heat
from impact collisions and ejected from the resulting crater.

Researchers saw that the highlands had more craters than the marea.
This meant they had been hit with more impacts so the highland rocks
were relatively older. But once they had the rocks in hand, they
could determine their absolute age in years.

This enabled them to make a template that could work anywhere in the
solar system. The Moon showed that a site with rocks of a certain
age would have a predictable number of craters of different sizes.
And since the rate of impacts was presumably similar throughout the
solar system, the lunar dates could be used as a benchmark to
estimate the age of surfaces elsewhere.

"This was a key thing, that impact was a significant and fundamental
phenomenon that affected not only the Moon and planets, but life
itself," said the planetary geologist Paul D. Spudis, of the Lunar
and Planetary Institute in Houston. "We had known that impacts
occurred, but until the rocks, we had viewed them as a geological
oddity."

No longer. In the early 1980s, scientists were able to show that
terrestrial mineral and crystal deposits 65 million years old were
similar to those found routinely in lunar ejecta. This led to the
now widely accepted theory that the consequences of an asteroid
impact had wiped out the dinosaurs.

Lunar scientists now suspect this insight may have further
implications. Analysis of the lunar samples and impact craters has
shown that the Moon's surface was solid 4.3 billion years ago, yet
the oldest impact rocks among the samples are 3.9 billion years old.

Some researchers have suggested that impacts on the moon began to
taper off 4.3 billion years ago, only to resume with a vengeance in
a "cataclysm" 400 million years later. And if the cataclysm affected
the Moon, it also affected the Earth -- at a time when life was just
beginning.

"This is very controversial," said Charles Shearer, a lunar
scientist at the University of New Mexico and the chairman of the
lunar lab's peer review committee. "It's probably important to
sample other terrains."

This is part of the lure of Mr. Bush's lunar initiative, which calls
for a base near the South Pole and exploration of the Moon's entire
surface, including the far side. These possibilities, Mr. Allen
said, "have the scientific community really jazzed."

But not everyone. "It is very difficult to justify the Moon as a
primary goal for human spaceflight -- there's not enough new to find
out," said Robert Zubrin, president of the Mars Society and a critic
of renewed lunar exploration. "If we want a challenge, Mars is it.
Are you really going to inspire the youth of today by repeating the
technological feats of their grandparents?"

One of these "grandparents" is a University of Tennessee lunar
geologist, Lawrence A. Taylor, 70, an expert on regolith. He has
developed ways to extract oxygen from the lunar dust, and, based on
the knowledge that regolith contains metallic iron, he patented a
method of microwaving the soil to transform it into a glass that can
be used as a hard surface for spacecraft landings and takeoffs or
for roads.

Mr. Taylor has also developed a way to "vacuum" iron particles from
lunar dust using a tube filled with electromagnets. And he is on
NASA committees advising medical doctors on astronaut health and
engineers on lunar habitat.

"People have started calling on me right and left," Mr. Taylor said.
"For years people contacted me mainly out of curiosity, but now I'm
in the limelight."