[meteorite-list] You're no Sun of mine!

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Fri Apr 7 00:21:16 2006
Message-ID: <nnnb32tium9aluin0pkauvdsnm6nto6g68_at_4ax.com>

http://www.abc.net.au/news/newsitems/200604/s1610398.htm

Sun research yields unexpected results
By Judy Skatssoon for ABC Science Online

Analysis of the first sample of lunar soil collected by Neil Armstrong has
thrown into disarray what researchers believe about the Sun, an international
team of scientists says.

Dr Trevor Ireland from the Australian National University and colleagues report
in the journal Nature the results of a study of oxygen isotopes on the surface
of soil grains returned to Earth by the 1969 Apollo 11 mission.

It was hoped the study would provide clues about the chemical make-up of the Sun
and the proto-planetary soup that gave birth to our solar system.

In particular, researchers hoped to find evidence for either of the two reigning
theories about the Sun's composition.

According to one theory, the Sun has a similar oxygen composition to the
planets.

The other theory suggests it has enriched levels of the isotope oxygen-16.

Instead, the study indicates that while the Sun is dissimilar to bodies like the
Earth and meteorites, it has lower levels of oxygen-16 than expected.

"This was a completely unexpected result for us," Dr Ireland said.

"Our Sun is not the Sun that we thought it was."

Dr Ireland says the finding also suggests the Sun somehow ended up with a
different composition from the cloud of dust and gas that preceded it.

He says this is based on other small rocky bodies, known as carbonate
chondrites, which are the oldest known things in the solar system and have up to
500 times more oxygen-16 than other oxygen isotopes.

Solar winds

Dr Ireland says while we cannot get samples directly from the Sun, we can infer
its composition by looking at lunar samples, which are believed to reflect its
composition.

This is because lunar soil contains oxygen isotopes "implanted" by solar winds
carrying elements blown out from the Sun.

But after using a caesium beam to erode the surface of the soil grains and
measure the isotopes oxygen-16, oxygen-17 and oxygen-18, the researchers
discovered unexpectedly low levels of oxygen-16.

"We found that the oxygen ... did not agree with either a planetary composition
or the oxygen-16 rich composition," Dr Ireland said.

"The oxygen isotopes are 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 that comprises the Sun versus the planets."

Dr Ireland says an analysis of oxygen from Jupiter's atmosphere, comets and
other bodies in the solar system could shed more light on the mystery.

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Received on Thu 06 Apr 2006 11:41:50 PM PDT