[meteorite-list] Meteorite dates lunar volcanoes *Picture of Kalahari 009*

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Sun, 9 Dec 2007 16:28:47 -0800
Message-ID: <93aaac890712091628x7683b52cg6000dfc6b988c3c6_at_mail.gmail.com>

Hello All,
Unsure if this article has already been posted, but it hasn't arrived
in my inbox yet, so here goes.
Article text below; see link for the picture.
Jason

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http://news.bbc.co.uk/2/hi/science/nature/7128000.stm
Meteorite dates lunar volcanoes
Volcanoes were active on the Moon's surface soon after it was formed,
a new study in the journal Nature suggests.
Precision dating of a lunar rock that fell to Earth shows our
satellite must have had lava erupting across its vast plains 4.35
billion years ago.
This is hundreds of millions of years earlier than had been indicated
by the rocks collected by Apollo astronauts.
Scientists say the information will help us better understand the
beginnings of the Solar System.
And they urge future Moon missions to try to obtain more of these most
ancient rocks.
"We want to understand how the Solar System formed, how the planets
formed," said Mahesh Anand from the UK's Open University.
"The Moon is the only place where you can go to find the first 500
million years of geological history, because these old rocks have been
lost on Earth," he told BBC News.
Botswana fortune
According to the favoured theory, the Moon was created some 4.5
billion years ago in a smash-up between the Earth and a Mars-sized
body.
Material thrown into space is believed to have coalesced to become our
satellite.
Volcanism on this new object would not have started until its surface
had cooled to form a crust and its insides had become separated into a
mantle and a core. Quite when this might have happened has been hard
to pin down.
Virtually none of the basaltic rocks collected by moonwalkers are
older than 3.9 billion years; but with less than 400kg of lunar
material returned to Earth, many scientists suspected Apollo would not
be the last word on the subject.
Now, Dr Anand - working with Dr Kentaro Terada, from Hiroshima
University, Japan, and other colleagues - has put a new date on a
lunar meteorite known as Kalahari 009.
Sometime in the past, this 13.5kg volcanic rock was blasted off the
Moon by the impact of an asteroid or comet and fell to Earth in what
is now Botswana.
Moon knowledge
Scientists know it comes from the Moon because of the type of oxygen
atoms it contains.
And by looking closely at the ratio of uranium and lead atoms in the
rock's phosphate minerals, the team has also been able to say when the
basalt was ejected - 4.35 billion years ago, give or take 150 million
years.
"The age of the phosphate is the age of the rock," said Dr Anand,
"because the rock solidifies when the magma cools, and when the magma
cools the mineral forms.
"Volcanic activity is a secondary process. A planet has first to form,
solidify, and separate into layers; and then there is melting of that
solidified mantle to produce volcanism.
"So we are pushing all of this further back in time; and [our
research] suggests these processes took place over a much shorter
timescale than had previously been thought."
New interest
Space agencies have renewed their interest in the Moon three decades
after the Apollo landings.
Europe's recent Smart-1 orbiter has been swiftly followed by Japanese
and Chinese spacecraft.
India will be next; and in the coming decade we should see robots land
on the lunar surface, with astronauts set to return by 2020.
Scientists say the Moon has much to tell us about the early Earth. The
surface rocks on our planet are relatively young because they are
constantly recycled into the interior.
The not-so-dynamic Moon, on the other hand, has an abundance of early
material on its surface. Researchers think it should even harbour
ancient Earth meteorites - rocks that travelled in the opposite
direction to Kalahari 009.

Received on Sun 09 Dec 2007 07:28:47 PM PST