Someday I'm going to have to get around to subscribing to Nature.

It's an interesting idea, and when I checked the "Lunar Sourcebook" it did note that there was an oddness in the 15N/14N ratio, described as such:

"Careful isotopic measurements of the N extracted from recently exposed soils and from a series of old regolith breccias, which trapped solar wind as much as 3.5 b.y. ago, show an increase in the 15N/14N ratio of about 50% or about 15% per b.y. This result, which has been reinforced by more recent measurements, is still not explained."

Later in the book, when dealing with Lunar chemistry, it notes under "Solar nitrogen anomalies" that

"the old, immature (not much exposed to Sun) soils in the Apollo 17 deep-drill core have the 15N/14N ratios some 7% lower than that of the present terrestrial atmosphere, while the young, mature (much exposed to Sunlight) soils have values closely approaching the terrestrial value. Such isotopic anomalies for N have been tentatively interpreted as the result of a secular increase in the 15N/14N ratio of solar-wind N"

I like the idea of getting samples from the far side. It would have never been directly exposed to anything streaming out from Earth presumably in the magnetotail. It would provide an interesting comparison.

Yet another example of the unfinished science which awaits us on our Moon.