[meteorite-list] Poor Man's Space Probe (Meteorites)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Jan 10 15:03:05 2005
Message-ID: <200501102002.MAA01174_at_zagami.jpl.nasa.gov>

http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1380&mode=thread&order=0&thold=0

Poor Man's Space Probe
Astrobiology Magazine

Summary - (Jan 09, 2005): To see the world in a grain of sand has a resonant
poetry when astronomers try to understand the rain of dust and meteors
that blanket the Earth daily. It turns out that doing astronomy with a
microscope has its benefits, particularly when the extraterrestrial
samples arrive at our doorstep.

  
Poor Man's Space Probe
Astronomy Through a Microscope
by G. Turner

William Blake's vision: "To see a world in a grain of sand" is being
realised by a group of researchers at the University of Manchester.
Their work, which involves analysing minute samples of material of
extraterrestrial origin, is shedding new light on the origin of our
planet and the Solar System. They are among the world-leaders in this
seemingly esoteric field.

The samples come from meteorites - fragments of rock that have crashed
through the Earth's atmosphere from space. Most meteorites consist of
the debris left over from the formation of the planets, which is why
their analysis is important in understanding the origin and evolution of
the Solar System, and the Earth's place within it. In the near future
the researchers will have access to even more significant samples -
those brought back by space missions to comets and our nearest planetary
neighbour Mars.

Although meteorites are sometimes known as 'the poor man's space probe',
these remarkable objects require sophisticated (and expensive)
instruments to extract their primaeval secrets. The Manchester group has
developed new analytical techniques and instruments to study meteorites,
which have benefited other areas of study, particularly the earth
sciences and materials science.

In a sense they are heirs of the 19th-century Sheffield industrialist
Henry Clifton Sorby, who showed that you could understand how mountain
ranges develop by looking at slivers of rock through the newly invented
petrological microscope. Sorby developed his microscope to study the
grains of iron-nickel alloy found in meteorites, and then went on to
show how it could be used to understand and improve the properties of
Sheffield steel. This must surely be the earliest example of an academic
interest in 'space research' leading to industrial benefits.

Since then, the study of meteorites has brought together physicists,
chemists, geologists and astronomers, and has been a fertile breeding
ground for advances that have taken earth sciences into space and
brought astronomy into the laboratory.

The first signs of that amalgamation came with the advent of the Apollo
Moon landings in 1969. A dozen or so UK research groups contributed to
the program, the largest number outside the US. Among them was Grenville
Turner, then a young lecturer based at Sheffield University, who
developed a new method for dating rocks, called argon-argon dating.
Aside from producing the first accurate ages of the lunar surface, it
provided the basis for current estimates of the probability of large
extraterrestrial bodies striking the Earth. The technique is also now
routinely used in the earth sciences and has spawned a mini industry of
specialist mass-spectrometer builders, a field in which UK industry
still has a leading international role. Mass spectrometers are used to
measure abundances of isotopes and can be used to study a wide range of
physical and chemical processes in nature.

In Manchester we also built in 1999 the first of a new breed of
instruments capable of analysing samples as small as a few hundred
atoms. The results of a recent measurement reported in the research
journal Science show the presence of the isotope xenon-129, produced
from the radioactive decay of a now-extinct isotope, iodine-129, which
was itself produced in an exploding star. Found in tiny grains of halite
(rock salt) in a primitive meteorite along with minute inclusions of
water, it provides evidence that liquid water, a critical component of
life, was flowing through the precursors of the planets within 2 million
years of the Solar System's birth.

The most remarkable discovery in recent years has been the isolation of
'stardust'. These are minute grains of diamond, silicon carbide,
graphite and corundum (aluminium oxide) which condensed in the
atmospheres of stars, millions of years before the birth of our Solar
System. In their bizarre isotopic signatures they carry a story of how
the chemical elements, which came together to make up the Earth and
ourselves, were generated by nuclear processes in the interiors of long
dead stars. Current methods for isolating these 'pre-solar grains' are
decidedly crude and involve dissolving most of the meteorite in strong
acids. The process is sometimes described as 'burning down the haystack
to find the needle' and raises the question, still to be answered, of
what information is being lost with the haystack!

The first extraterrestrial samples to be returned to Earth, since
Apollo, will arrive later this decade in 2006. These will be grains of
dust collected by the NASA Stardust mission from the comet Wild. Comets
are frozen relics of the material which accumulated to form the Solar
System 4570 million years ago, a time capsule of our own beginnings.
Captured in aerogel, a man-made silica-based solid barely 10 times as
dense as the air we breath, the sample will consist of several thousand
grains less than one-tenth of a millimetre across. Their analysis will
demand the development of a new breed of analytical instrument with
unpreced-ented sensitivity at the atomic scale.

Sometime before 2010, samples of Mars will also be returned to Earth and
be subjected to the barrage of techniques, which only the vast array of
laboratory-based equipment makes possible. Comparison with the effect of
the lunar sample programme in the 1970s suggests that the critical
technologies developed to analyse these unique samples, and those of
cometary grains, which precede them in 2006, will have a major
cross-fertilization into analytical instrumentation in other fields.

Much has changed since Sorby's time. Optical microscopes, electron
microscopes and many other kinds of sophisticated instrument are now
essential tools in fields as diverse as earth and planetary science,
semiconductor research, forensic science, nanotechnology, the
micro-environment, and so on. But some aspects remain the same - the
complex interplay of fundamental science and technology continue to
enhance our lives.

------------------------------------------------------------------------

Professor G.Turner is Professor of Isotope Geochemistry and head of the
Cosmochemistry Research Group at the University of Manchester. (This
feature is based on an article that appeared in Science and Parliament)
Received on Mon 10 Jan 2005 03:02:14 PM PST