[meteorite-list] SMART-1 On The Trail Of The Moon's Beginnings

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Aug 18 17:01:08 2006
Message-ID: <200608182058.NAA14406_at_zagami.jpl.nasa.gov>

http://www.esa.int/esaCP/SEM1RHBUQPE_index_0.html

SMART-1 on the trail of the Moon's beginnings
European Space Agency
18 August 2006

The D-CIXS instrument on ESA's Moon mission SMART-1 has produced the
first detection from orbit of calcium on the lunar surface. By doing
this, the instrument has taken a step towards answering the old
question: did the Moon form from part of the Earth?
 
Scientists responsible for the D-CIXS instrument on SMART-1 are also
announcing that they have detected aluminium, magnesium and silicon. "We
have good maps of iron across the lunar surface. Now we can look forward
to making maps of the other elements," says Manuel Grande of the
University of Wales, Aberystwyth UK, and D-CIXS' Principal Investigator.

Knowing how to translate the D-CIXS orbital data into "ground truth" has
been helped by a cosmic coincidence. On 9 August 1976, the Russian
spacecraft Luna 24 was launched. On 18 August it touched down in a
region of the Moon known as Mare Crisium and returned a sample of the
lunar soil to Earth.

In January 2005, SMART-1 was high above Mare Crisium when a giant
explosion took place on the Sun. Scientists often dread these storms
because they can damage spacecraft but, for the scientists responsible
for D-CIXS, it was just what they needed.

The D-CIXS instrument depends on X-ray emission from the Sun to excite
elements on the lunar surface, which then emit X-rays at characteristic
wavelengths. D-CIXS collects these X-ray fingerprints and translates
them into the abundance of each chemical element found on the surface of
the Moon. Grande and his colleagues could relate the D-CIXS Mare Crisium
results to the laboratory analysis of the Russian lunar samples.

They found that the calcium detected from orbit was in agreement with
that found by Luna 24 on the surface of Mare Crisium. As SMART-1 flew
on, it swept D-CIXS over the nearby highland regions. Calcium showed up
here too, which was a surprise until the scientists looked at the data
from another Russian moon mission, Luna 20. That lander had also found
calcium back in the 1970s. This boosted the scientists' confidence in
the D-CIXS results.

A shocking birth for the Moon?

Ever since American astronauts brought back samples of moonrock during
the Apollo Moon landings of the late 1960s/early 1970s, planetary
scientists have been struck by the broad similarity of the moonrocks and
the rocks found deep in the Earth, in a region known as the mantle. This
boosted the theory that the Moon formed from debris left over after the
Earth was struck a glancing blow by a Mars-sized planet.

However, the more scientists looked at the details of the moonrock, the
more discrepancies they found between them and the earthrocks. Most
importantly, the isotopes found in the moonrocks did not agree with
those found on Earth.

"The get-out clause is that the rocks returned by the Apollo missions
represent only highly specific areas on the lunar surface and so may not
be representative of the lunar surface in its entirety," says Grande;
hence the need for D-CIXS and its data.

By measuring the abundance of several elements across the lunar surface,
scientists can better constrain the contribution of material from the
young Earth and its possible impactor to condense and form the Moon.
Current models suggest that more came from the impactor than from Earth.
Models of the Moon's evolution and interior structure are necessary to
translate the surface measurements into the Moon's bulk composition.

D-CIXS was a small experimental device, only about the size of a
toaster. ESA is now collaborating with India to fly an upgraded version
on the Indian lunar probe Chandrayaan, due for launch in 2007-2008. It
will map the chemistry of the lunar surface, including the other landing
sites from where samples have been brought back to Earth. In this way it
will show whether the Apollo and Russian landing sites were typical or
special.

"From SMART-1 observations of previous landing sites we can compare
orbital observations to the ground truth and expand from the local to
global views of the Moon," says Bernard Foing, Project Scientist for
SMART-1.

Then, perhaps planetary scientists can decide whether the Moon was
indeed once part of the Earth.

 
 
Note to editors
 
The findings will appear in the Planetary and Space Science journal, in
an article titled: "The D-CIXS X-ray spectrometer on the SMART-1 mission
to the Moon ??? First Results", by M.Grande et al.
 
 
For more information
 
Manuel Grande, D-CIXS Principal Investigator, University of Wales,
Aberystwyth, UK
Email: m.grande _at_ rl.ac.uk

Bernard Foing, ESA SMART-1 Project scientist
Email: bernard.foing _at_ esa.int
Received on Fri 18 Aug 2006 04:58:14 PM PDT