New Lunar South Polar
Maps From SMART-1
(11 March 2008) Newly-released images of the lunar south-polar region obtained by ESA's SMART-1 are proving to be wonderful tools to zero-in on suitable study sites for potential future lunar exploration missions.
This mosaic of the lunar south pole was obtained with images taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA's SMART-1. The pictures were taken between Dec 2005 and March 2006, during lunar southern summer. When obtaining the images, SMART-1 was flying over the south pole at a distance of about 500 km, allowing individual images with small-field (about 50 km across) high resolution views (50 m/pixel). Each individual image includes areas imaged with colour filters and a more exposed area. The differences have been corrected accordingly to obtain this mosaic. The mosaic, composed of about 40 images obtained over more than 30 orbits, covers an area of about 500 by 150 km. The lunar near-side facing Earth is at the top of the map, while the far-side is at the bottom. (courtesy: ESA/SMART-1/Space-X (Space Exploration Institute))
SMART-1's Advanced Moon Imaging Experiment
(AMIE) has collected many images of the lunar south-polar region, with
unprecedented spatial resolution. The images, obtained over a full year of
changing seasons were used to study the different levels of solar illumination
on the Moon's surface.
The orientation of the lunar rotation axis is
such that the Sun just about grazes the lunar poles, leaving some regions
permanently shadowed.
Shackleton crater is located in the inner ring of
the south pole Aitken basin, the largest known impact basin in the solar
system. It has a diameter of 2600 km.
The south pole is located on the
rim of Shackleton crater. SMART-1 took images around the crater, which is a
strong contender for a future robotic and human exploration site and for a
permanent human base.
The polar mosaics show geological features of
interest within reach from the south pole. Monitoring of the illumination of
selected polar sites has allowed scientists to confirm that a ridge located 10
km from the Shackleton rim is prominently illuminated, and could be a strong
contender for a potential future lunar outpost.
The large number of
impact craters in the area indicates that the terrain is ancient. An example is
crater Amundsen, 105 km in diameter, lying 100 km from the pole. It shows
central peaks and asymmetric terraces that deserve geological and geochemistry
studies.
The Lunar Prospector mission had previously indicated evidence
of enhanced hydrogen in the permanent shadowed floors of polar craters,
possible sign of water ice - a relevant element when choosing a human
outpost.
As to whether or not ice could still be trapped under the floor
of polar craters, the former SMART-1 Project Scientist Bernard Foing said, "To
understand whether or not water is possibly present at the south pole, we have
to take into account the following factors: how volatile elements were
delivered to the lunar surface by comets or water-rich asteroids, whether they
were destroyed or persisted under a dust cover and for how long they were able
to accumulate."
"The polar regions are still lunar incognita, and it is
critical to explore them and study their geological history," he
added.
Using SMART-1 images, SMART-1 AMIE investigators and US
collaborators have also counted small impact craters on Shackleton ejecta
blanket to estimate the age of the crater. They have found that the number of
craters is twice that of Apollo 15 landing site, which would make the
Shackleton crater between 3.6 to 4.3 thousand million years
old.
"Previous investigators believed Shackleton to be much younger, but
that could be due to grazing illumination at the poles, which enhances the
topography, mimicking a younger crater."
So, in view of SMART-1
observations, the south polar site looks even more interesting with the
confirmation of prominently-lit sites, and the indication of old craters where
ice could have had more time to accumulate in permanently-shadowed
areas.
"The SMART-1 south polar maps indicate very exciting targets for
science and future exploration, within travel reach from a rover or humans at
the south pole", says Jean-Luc Josset, Principal Investigator for the
AMIE.
These high-resolution SMART-1 south polar mosaics were produced
and analysed in the framework of a study project for the design and operations
of lunar polar robotic landers and rovers, by Marina Ellouzi, a Master's
student in space engineering at the Paris-Meudon Observatory. The south polar
mosaics, SMART-1 highlights, and results on the geology and illumination of
Shackleton crater are being presented and discussed by the SMART-1 AMIE team
and collaborators at the 39th Lunar and Planetary Science Conference at League
City, Texas between 11-12 March 2008.
(source: ESA)
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