The Moon’s rocky clues – and what they reveal

Not long after landing on the Moon, Neil Armstrong pocketed the first Moon rock. You can see the regolith brecchia here. 

In the end, the six Apollo missions brought back 2,200 samples of Moon rocks, totalling 282 kilograms. Those samples – along with about 300 grams from automated Soviet spacecraft – are kept in a sample building at the Johnson Space Centre in Houston, Texas.

Every year, about 400 samples are then shipped to scientists or loaned to museums to learn about the history of the Moon, the Earth, and the Solar System.

Those samples tell a smashing tale. They show that Moon rocks are similar to those on Earth – they have matching isotopes. That in turn has led to the theory that the Moon formed when a celestial body struck baby Earth 4.5 billion years ago, and the debris created coalesced into today’s Moon.

A new study published in Nature argues that ancient impacts have revealed rocks that future missions will be able to understand.

That in turn will “provide insight into fundamental planetary processes, including differentiation and magmatic evolution”.

The authors write that while 50 years of lunar science have given us a framework for understanding lunar evolution, gaps remain. In fact, they say that because existing samples covered only a small section of the lunar surface, it’s “grossly incomplete”.

The question is, then, how to fill those gaps. The authors argue that future missions should target materials in impact basins, and look for candidate rock types that can teach us more about the Moon’s unknown unknowns.

(On a side note, they point out that there is a “large portion” of the existing samples that remain unstudied.)

The Moon is an “accessible laboratory for developing and refining the framework of planetary formation and evolution”, they write.

Lunar asymmetries are another fertile field for exploration. The nearside and the farside of the Moon have big differences in the thickness of the crust, as well as its geochemistry, and volcanic activity. “What is the origin of the asymmetries, and what are the implications for mantle materials exposed by lunar basins?,” they ask.

And, as future crewed missions to the Moon loom, new findings will have “fundamental implications for solar system science”, they write.  

“In a time of renewed interest in lunar exploration by NASA, its commercial partners, and international agencies, new generations of planetary scientists have a clear path towards furthering our understand of the Moon and beyond.”

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