The new Moon: A view
Authors: Hinners N. W. 
Published: February 2008

A review of Apollo 11, 12, and 14 and Luna 16 data shows that a genuine step‐function increase has occurred in our understanding of the moon. This results largely from the ability to conduct detailed analyses, most of which cannot be done by remote means, on returned sample. Geophysical data from Apollo‐emplaced science stations is a valuable complement to the new sample knowledge. It is evident that the great store of data previously gathered from earth‐based telescopic observations and unmanned spacecraft and the interpretations of it are enabling us to construct much better lunar models than otherwise possible. Without this pre‐existing framework, the lunar samples acquired would be of diminished value. The lunar ‘sum total experience’ will reach beyond the moon and should be particularly valuable in interpreting remotely sensed data from Mars and other planets.

It appears that the moon originated about 4.6 b.y. ago, as did the earth and meteorites, thus at the beginning of the solar system. It seems to have suffered most of its internal thermal spasms in the first 1 or 2 b.y. of life and has been slowly dying since, in contrast to the earth, which today may be as active as ever. The lunar surface was exposed to a large but rapidly decreasing flux of infalling objects in its first 1½ b.y., some of which might have been part of the accretionary population that evidently formed the moon. That activity has been at a greatly diminished level for the past 3 b.y. and may now be comparable to the action of solar and galactic atomic particles in effecting surface modifications.

The igneous processes that resulted in flooding of the mare basins with basaltic lavas are now reasonably well understood, as are the effects of meteoroids in generating the shallow (meter scale) surficial soil or regolith. Processes responsible for modification of the near‐surface layer (micron scale), which gives rise to the remotely sensed spectra, are not wholly clear. Evidence exists that the lunar near‐surface highlands are compositionally heterogeneous, but neither the mare basalts nor Imbrium ejecta (Fra Mauro) can be representative of the lunar deep‐interior composition. However, a good model of the ‘primordial’ or existing interior composition does not yet exist, although geochemical and geophysical evidence indicates that the deep interior may represent accreted material that has never been above the melting point. On the other hand, the outer regions have undergone severe chemical modification. These outer regions are, and probably always have been, depleted in volatile elements and enriched in refractories, an observation constraining models of lunar origin.

All basic models of lunar origin (capture, dual‐planet, earth‐fission) are alive, although the idea of direct fission from earth is quite sick. Sicker yet, and essentially dead, are tektites‐ and meteorites‐from‐the‐moon hypotheses. The meteorite evidence does indicate, though, that processes similar to those forming lunar‐mare basalts occurred at other places in the early solar system.

Questions relating to the origin of life must await future planetary exploration, for no life forms have been found, nor have organic molecules been unambiguously identified as being indigenous to the moon. The virtually complete lack of water and the 4+ b.y. of exposure to a harsh space environment make eventual detection of lunar life unlikely.