What the Apollo Rock Samples Revealed About the Moon
The lunar rocks changed what scientists thought they knew about our satellite, but raised many more questions.
Here’s how Richard W. Carlson begins his article in Science Magazine: “The analysis of lunar samples returned to Earth by the Apollo and Luna missions changed our view of the processes involved in planet formation.” Change is good, but in science, it implies that what was formerly taught as fact was not entirely true. So is what they are saying now true? “Ground truth” (onsite data) is far better than telescopic or orbital data about the moon, but even now, we only have about 800 pounds of lunar rocks from very near the surface at half a dozen sites (plus a few more by Russian robotic Luna spacecraft), all gathered near the moon’s equatorial regions. And even though these rocks can be examined down to the atomic level by multiple methods, the findings are often filtered through worldview assumptions.
Determining whether the data obtained from Apollo and Luna samples can be extrapolated to the whole Moon, or whether they constitute a biased record heavily influenced by the nearside basin-forming events, can only be addressed by sample returns from new locations well removed from the Apollo and Luna sites.
So as we look at Carlson’s “Analysis of lunar samples: Implications for planet formation and evolution,” beware the temptation to think it’s the last word.
The analysis of lunar samples returned to Earth by the Apollo and Luna missions changed our view of the processes involved in planet formation. The data obtained on lunar samples brought to light the importance during planet growth of highly energetic collisions that lead to global-scale melting. This violent birth determines the initial structure and long-term evolution of planets. Once past its formative era, the lunar surface has served as a recorder of more than 4 billion years of interaction with the space environment. The chronologic record of lunar cratering determined from the returned samples underpins age estimates for planetary surfaces throughout the inner Solar System and provides evidence of the dynamic nature of the Solar System during the planet-forming era.
But that is not entirely true. Repeatedly for over a decade, CEH has reported (from scientific journals) major problems with crater-count dating. Some geophysicists have complained that one cannot say anything definitive about the age of a surface from craters. Here, Carlson just said that craters underpin age estimates for the rest of the inner solar system. The theory is hitched to a wayward horse!
At much larger scales, remote observation of the Moon shows the lunar highlands to be more heavily cratered than the mare basins. This provides a relative chronology for the lunar surface [no it doesn’t], showing the mare to be younger than the highlands. Converting this relative crater chronology into an absolute chronology for the lunar surface became possible through analysis of the samples returned by Apollo. Age determinations for rocks from the lunar surface allowed calibration of the lunar impact flux through time (Fig. 4).
But absolute chronology depends on assumptions about radiometric dating, which are dubious (see ICR). So now Carlson rides a wayward horse in quicksand, and then shouts “Yee-haw!” taking off on a gallop through the solar system.
This flux estimate can be extrapolated throughout the inner Solar System, allowing the cratering record for other planets and moons to be turned from relative to absolute chronologies for their surfaces. Such data provide basic information on the rate of planetary resurfacing either destructively by erosion, or constructively by volcanism, with the latter providing key information on the dynamics of planetary interiors.
Volcanism happens, and leaves scars. Erosion happens, and leaves scars. Neither of these processes, however, tell how long they took. Planetary moyboys, looking through their long-age glasses, see millions and billions of years that nobody ever witnessed. They have to, in order to give Darwin time to evolve humans from bacteria.
Looking for Uncooperative Data
Whenever scientists propose a theory about a history nobody ever saw, they are going to have problems. Secular planetary scientists are convinced of billions of years before they look at a moon rock. It takes an outsider to recognize that the puzzle pieces don’t quite fit reality. Carlson acknowledges numerous problems with secular theories.
Out with the old cold: Scientists had to start over when they got the rocks, because what they thought they knew was wrong:
Prior to the Apollo landings, the following statement represented the prevailing view of terrestrial planet formation: “It seems possible and indeed probable that the earth could and did accumulate below the melting point of silicates throughout its entire growth from a small size to its present one”. This reflected the opinion that planets grew by the gentle accumulation of asteroid-sized planetesimals, so that high temperatures only occurred locally in some of the larger impacts. The samples collected during the Apollo 11 mission in 1969 quickly disproved the idea that planetary bodies, even ones the size of our Moon, started out cold.
Floating new theories: The rocks showed high abundances of anorthosite, a low-density mineral that scientists deduced must have floated above a magma ocean to form the crust. Thus the hot-moon theory took hold over the cold-moon theory.
KREEPY data: But among the anorthosite, there were detectable abundances of potassium (K), rare-earth elements (REE), and phosphorus (P). These elements should have been (in theory) in the magma below the crust that floated. The lunar maria, or large impact basins, were especially KREEPY. Scientists had to modify the theory to account for the anomalies by adding in late volcanism. Nothing was simple any more.
The restricted areal distribution of KREEP could reflect the presence of a KREEP layer beneath the whole crust that was only excavated to the surface by impacts large enough to penetrate through the crust. However, the largest impact basin on the Moon, the South Pole–Aitken basin, shows only slightly elevated abundances of thorium (Fig. 2). Alternatively, both the apparently asymmetric distribution of KREEP and the thicker lunar crust on the farside than on the nearside have led to proposals that the asymmetry originated in the magma ocean era by either gravitational or thermal interaction with Earth. The concentration of radioactive KREEP into a smaller portion of the Moon also could have provided a heat source to explain both mare basalt volcanism that continued for more than a billion years after the Moon solidified and the higher number of large impact basins facing Earth than on the lunar farside.
Post facto rationalization. It’s easy after you have a sample containing a surprise to claim that your new theory, devised after the sample was analyzed, was actually predicted by the theory.
Some mare basalts have compositions similar to terrestrial basalts, but others have distinctively high contents of titanium. These unusual lunar lava compositions most likely reflect a wide range in the composition of the rocks in the lunar interior that melted to create these lava flows. This type of compositional diversity in the lunar interior is predicted by the magma ocean model, as it fits the sequence of dense mineral accumulation that would occur as the magma ocean cooled and crystallized.
Time dilation. Another post-facto prediction is shown in this statement about age anomalies. The moon should have cooled too quickly to fit the evolutionary timeline, but since it didn’t, the new model must have predicted that, too!
Further evidence in support of a lunar magma ocean comes from measurements of the isotopic composition of elements that receive the decay products of naturally occurring radioactive isotopes. Unless a magma ocean has a thick insulating crust, or atmosphere, above it, heat loss to space causes cooling and crystallization of the magma in a few million years or less—a time that is short relative to the chronological resolution of many radioactive clocks used to determine the age of rocks.
Foggy bottom line. If you think the radiometric dating of moon rocks proved an old moon, read these admissions. Carlson chalks up the resolution of multiple anomalies to futureware.
If they formed by direct crystallization of the lunar magma ocean, the rocks of the highlands crust should show little variation in age, corresponding to the date of magma ocean crystallization. The data, however, show a dispersion in ages for different highland rocks. Whether this reflects the range in actual crystallization ages, or resetting of the radiometric clocks in the samples by slow cooling deep in the crust or by impact-related metamorphism, is unclear. Modern applications of radiometric dating techniques are narrowing the age range of the crustal rocks to 4.36 to 4.40 billion years, 150 to 200 million years after the start of Solar System formation. Resolving the age range of the lunar crust is made difficult by the small number of returned crustal samples appropriate for dating and the fact that the oldest crust on the Moon has been repeatedly pummeled by impacting objects. Obtaining a clear answer to the age of the magma ocean, and the lunar crust in general, likely will require a broader collection of crustal rocks to be returned from the Moon.
More KREEPY data. If simplicity is a virtue of scientific theories, this one has data wandering all over the map.
Another prediction of the magma ocean model is that the anorthositic crust, KREEP, and the accumulated crystals in the lunar interior that would later be melted to produce mare basalt lavas all formed over a relatively short time interval. Radioactive dating of mare and KREEP basalts indicates eruption ages from 4.25 to 2.9 billion years ago. At the time of their eruption, however, the basalts were characterized by a wide range in the relative abundances of the isotopes that are produced by the radioactive decay of naturally occurring radioactive elements,
And now, something brand new. Carlson creeps up to the Giant Impact model, which replaced the post-Apollo magma ocean model. You can’t get a magma ocean by slow-and-gradual accretion, scientists concluded, because the radiometric dates implied that whatever happened “was determined by an event of duration less than a few millions of years,” contrary to secular theories that assumed the composition of each rocky body in the solar system must have been unique.
The magma ocean model implies that some energetic process involving high temperatures was involved in Moon formation. The nature of that process became clearer from comparison of the composition of lunar and terrestrial rocks. Early analyses of mare basalts were used to argue that the composition of the bulk Moon was similar to that of Earth’s mantle. Earth, Mars, and their presumed meteoritic building blocks have subtle stable isotopic differences that reflect imperfect mixing of the contributions of the many stellar nucleosynthetic events in the galaxy that created the elements in our Solar System before the planets began to assemble. Earth and the Moon, however, appear to share identical isotopic composition. This holds even for tungsten, which tracks the timing of core formation due to the radioactive decay of 182Hf to 182W. The timing of core formation is unlikely to be the same on two bodies of such different size as Earth and the Moon. The Moon thus appears to share a very close genetic relationship with Earth.
Return of the [modified] fission model, with tweaks. Carlson dates the fission model (that the moon spun off from the Earth) to “at least 1879” but hastens to add that it was physically impossible in its early form. The new Giant Impact Model tries to account for the two bodies’ isotopic similarities to a lucky interloper the size of Mars. But that creates new fine-tuning problems:
The compositional similarities of lunar and terrestrial rocks, however, revived the discussion of whether and how the Moon could have been derived from Earth. The focus turned rapidly to the question of whether a large impact into Earth could put enough material into stable Earth orbit to form the Moon. The answer appears to be “yes”, but exactly how is still being debated.
A new central dogma. Carlson tries to fine-tune the impact. Unless it was compositionally similar to the Earth, this Mars-sized body could not have contributed much material to the Earth or the Moon. And what kind of lucky glancing blow would send the crust into orbit instead of the mantle? Whatever happened, it is now christened the New Truth, because as all evolutionists know, design is just an illusion; the fact is that Stuff Happens. And there is no better stuff to happen than to have random impacts from somewhere out yonder to solve all the problems.
Although the role of giant impacts in more general aspects of planet formation remains unclear, the evidence for a lunar magma ocean and the Earth-Moon compositional similarity—both derived primarily from analysis of returned lunar samples—displaced the idea of cold, gentle planet assembly with one dominated by highly energetic impacts. As a result, the role of giant impacts is now an intrinsic part of models for planet formation, as are magma oceans as the initial stage of planet differentiation.
Houston, we’ve had a problem. Just as Carlson is granting supreme authority to the central dogma of impacts, somebody taps him on the shoulder and reminds him that a giant impact would obliterate all of Earth’s water (and other volatiles). And yet even the Moon has some evidence for water locked into some of its minerals (needless to say, the Earth is swimming in water). He goes back into theory-rescue mode. In a section called, “Keeping hydrated,” he admits the details are not clear.
Given the very high temperatures (several thousand kelvin) expected in a giant impact, more highly volatile compounds such as water were presumed to have been completely lost from the Moon. Hydrous minerals in lunar basalts are extremely rare, but whether this resulted from completely dry parental magmas or the loss of water from the magma during its eruption into the vacuum of the lunar surface was not clear. Deposits of volatile-driven pyroclastic volcanism—for example, the orange soils noticed by Apollo 17 astronaut Harrison Schmitt—were found at most Apollo sites and now have been mapped more widely from orbit. The identity of the gas fueling their explosive eruption is not clear.
Either-or, or neither-nor? Carlson waffles between the idea that volatiles and water got added after the Giant Impact by numerous small impacts, or whether the Earth and Moon both got their volatiles orginally. He doesn’t explain how original volatiles could have survived the big wallop, but he resurrects the notion anyway. Trouble is, both ideas have big problems.
The presence of water in lunar magmas has prompted reexamination of the fate of volatile elements during the giant impact. More generally, results from lunar sample analysis have driven a reinvestigation of the mechanism by which the terrestrial planets obtained water and carbon, with the implication that these volatile components may have been present when the terrestrial planets formed, rather than having been added later by accretion of icy bodies such as comets or icy asteroids.
Briefly noted: The article brings up other problems: Did the moon have a global magnetic field? He doesn’t ask whether its decay should worry earthlings about field decay at home. Carlson also ponders whether the alleged “Late Heavy Bombardment” was real or imaginary. So many questions remain after Apollo brought ground-truth rocks back home, that 800 pounds is not enough to answer them, except with futureware.
Humans conducted field work on the Moon for less than 12 days, covering a very limited portion of the Earth-facing side of the Moon. Refining the chronologic sequence of large impact events on the Moon requires more detailed field studies conducted in future visits that cover a larger portion of the lunar surface.
In summary, nothing is clear, but there’s always a need for more data.
A bit lengthy as it is, I hope you enjoyed this survey of findings from Apollo moon rocks. Anyone who thinks “we now know” the origin and history of the moon should ponder these statements as an unbiased observer. Cross out the assertions and worldview assumptions, and there is really a lot to doubt. Shouldn’t there be an opportunity for other ideas? For the last two days, we showed that the facts of the Moon indicate it is vital to life on Earth. So why not entertain the possibility that it was not an accident caused by a lucky smash-up, but that it was made for life’s benefit? Why must science repudiate the obvious?
Wernher von Braun, our creation scientist of the month, wrote in 1976 about the legacy of Apollo, citing an anecdote from the mission commander who read from Genesis while being among the first to orbit the moon:
When astronaut Frank Borman returned from his unforgettable Christmas, 1968, flight around the moon with Apollo 8, he was told that a Soviet Cosmonaut recently returned from a space flight had commented that he had seen neither God nor angels on his flight. Had Borman seen God? the reporter inquired. Frank Borman replied, “No, I did not see Him either, but I saw His evidence.”
Recommended Reading: Jonathan Sarfati at CMI has written a great article, “Apollo mission to the moon: 50th anniversary: What are the lessons for today?” He touches on a number of aspects, from hoax theories to lunar science to Christians who took part in the space program (including one of our contributors, Dr Henry Richter). He includes some little-known facts about the mission and gives Apollo a good look-back. Check it out! Also, there is a book by mathematician and astronomer Don DeYoung called, Our Created Moon. It would make for a good read during this remembrance of Apollo.