Professor Paul G. Lucey
Hawai'i Institute of Geophysics and Planetology

The (Potential) Surprising Science of the Poles of the Moon

The low obliquity of the Moon gives rise to permanently shadowed regions in
topographic depressions near the lunar poles.  Shielded from direct
sunlight, these regions will achieve very low temperatures, below 50K
according to some models.  Such surfaces will act as natural cold traps for
any volatiles which might encounter them.  Models of the evolution of the
Moon's orbit suggest that the current obliquity has persisted for over 2.5
billion years, so the lunar cold traps have been operating over a lengthy
and interesting period.  The recent Lunar Prospector mission provided
compelling evidence that hydrogen is concentrated near the poles in
positions corresponding to model cold traps.  While the popular presumption
has been that the hydrogen is borne by water ice, the vector of this
hydrogen is actually unknown.  Over time the lunar surface has intercepted
volatiles from comets, asteroids and other meteoritic material, the Sun and
even from giant molecular clouds through which the solar system
occasionally passes.  None of these sources can provide only hydrogen to a
polar cold trap, so the detected hydrogen is probably only the tip of the
iceberg and is a likely indicator of a diverse volatile deposit.  I will
review the many interesting issues related to the lunar poles and describe
a Discovery mission proposal recently submitted by UH to explore these
regions with a combination of remote sensing and in situ analysis