Scientists analyse solar wind from moon rock (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 11 Apr 2006 15:40:33 -0400 (EDT)
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Australian National University
Canberra, Australia
Further information:
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Jane O'Dwyer (02) 6125 5001 / 0416 249 231
Amanda Morgan (02) 6125 5575 / 0416 249 245
Friday 7 April 2006
Scientists analyse solar wind from moon rock
ANU scientists preparing for the analysis of solar wind samples from
NASA's Genesis mission believe they have already measured solar wind
particles in an analysis of lunar soil.
In the latest issue of Nature, Dr Trevor Ireland and his team from the
Research School of Earth Sciences at ANU detail how they found particles
in which oxygen isotope measurements did not fit those of the moon, the
planets, or of the earliest of meteorites.
"It was a completely unexpected result for us. We are confident that this
represents the solar wind, but by no means certain," Dr Ireland said.
"The real question our finding raises is why this solar composition
appears unrelated to the composition of the planets, the largest rocky
bodies in the solar system, or to refractory inclusions from meteorites
which have been regarded as solar condensates. Further study of samples
from the Genesis mission may have the answers."
Dr Ireland said that it was likely the particles identified with the low
oxygen abundance contained solar wind because the moon -- where these
samples came from -- is continuously buffeted by the solar wind, which is
essentially made up of charged particles ejected by the Sun.
The composition of the Sun is expected to provide significant clues as to
the history of the solar system. Our planetary system represents less than
1 per cent of the mass of the solar system and any differences between the
planets and the Sun must represent processes that operated in the early
solar system, or represent a different mix of components.
NASA's Genesis mission has returned to Earth samples of the solar wind for
analysis. It aims to obtain precise measure of solar isotopic abundances
such as oxygen, nitrogen, and noble gases.
To date, the isotopic composition of the Sun has been inferred for some
elements from lunar samples, but not oxygen because of its high abundance
in lunar minerals.
However, using the high-resolution, high-sensitivity ion microprobe
developed at ANU, called SHRIMP, the team were able to get an accurate
measurement of the solar oxygen isotopes in iron metal grains. "In many
ways, our measurements were our first attempt at scoping the experimental
difficulties we might have in measuring the Genesis samples and we had no
way of knowing beforehand that they would be analytically so successful,"
Dr Ireland said.
Dr Ireland said further analysis of oxygen from other solar system bodies,
such as from Jupiter's atmosphere and from comets, would provide a greater
comparative base for studies of the composition of the Sun.
"Perhaps the oxygen isotopes we found are simply telling us that the mix
of components in the Sun is different to that in the planets, particularly
in regard to the amount of dust versus gas. The Sun sources much of its
oxygen from carbon monoxide, which is essentially lacking from the
planetary bodies, which are derived from primordial dust," Dr Ireland
said.
IMAGE CAPTION:
[http://info.anu.edu.au/mac/Media/Media_Releases/_2006/_images/_April/alpha_lrg.jpg
(22KB)]
A scanning electron image of one of the iron metal grains analysed.
.
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