  One of the principal scientific reasons for wanting to resume in situ
exploration of the lunar surface is to gain access to the record it contains of
early Solar System history. Part of this record will pertain to the galactic
environment of the Solar System, including variations in the cosmic ray flux,
energetic galactic events (e.g, supernovae and/or gamma-ray bursts), and
passages of the Solar System through dense interstellar clouds. Much of this
record is of astrobiological interest as these processes may have affected the
evolution of life on Earth, and perhaps other Solar System bodies. We argue
that this galactic record, as for that of more local Solar System processes
also of astrobiological interest, will be best preserved in ancient, buried
regolith ('palaeoregolith') deposits in the lunar near sub-surface. Locating
and sampling such deposits will be an important objective of future lunar
exploration activities.
