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Moon Rocks and Moon Meteorites

On July 20th much of the world celebrated with the United States the 50th Anniversary of the first landing of men on The Moon. I went to Florida with my wife to Kennedy Space Center and was there on the actual anniversary day. It was a great experience. One thing that I noted, however, was the lack of moonrocks on display. I saw only three and I may have missed some others but I do not think so. I must say that the two I did see were quite interesting. They were very different from the samples of The Moon that I have seen as meteorites.

Lunar Sample 70035.40.020 Collected by Apollo 17 astronaut Harrison Schmitt near the Taurus-Littrow Valley region of The Moon. Weight 3.9 ounces (110 g)

There was one moon rock slice on display that you could touch.

Before the manned moon landings, we did not know what the rocks of The Moon were truly like. There were maps of what was believed to be the surface of our neighbor in space but it was based on remote studies from some probes and by observations from the ground. The lunar geologic maps of the Apollo era were very detailed and colorful but unlike geological maps of terrestrial areas, they showed mostly the type of terrain and the structural information about the areas. They might describe an area as a “plains” type region and assign it a color of dark salmon and a pLp label but say nothing of the rock types or mineralogy because that information did not exist yet. Phrases such as slightly hilly, hummocky, strongly steeped domes and a host of others described the places seen on the lunar surface. Only some general statements such as “likely volcanic rocks” were ever written in map publications. This changes and is still changing today from the study of the rocks returned by the astronauts. As a side benefit once scientists had actual moonrocks to study it was possible to identify some of the anomalous meteorites as actually originating on The Moon.

Just in the last few months, the archives of the Apollo moon rocks have been opened and some of the rocks stored untouched for fifty years have been brought out to be investigated. This is a tremendous development. Pristine rocks from The Moon can get studied with the latest equipment. It has been a best practice in archeology for a few decades to leave if possible some of a site untouched for future investigation as tools improve and focuses change. In the past, it was the wonderful sculptures, monuments, gold and silver objects and skeletal remains that were of great interest and now in many places, it is tiny fish bones and seeds and trade beads, small bits of textiles that are actually of more interest. These later items were often lost either entirely or at least their context by the bulldozer type archeology of two centuries ago. Hopefully, the refined techniques and better equipment of today will lead to many new discoveries from the Apollo returned rocks.

The Apollo Program only visited six locations on The Moon and though hundreds of pounds of rocks and soil samples were returned to Earth it was still just material from six locations. Scientists developed new technology and advanced the methods already on hand to define characteristics that moonrocks possess. These were characteristics most meteorites do not have. Scientist used this elemental and isotope signature of rocks from The Moon and soon found it within a few meteorites. The first question I am always asked about lunar meteorites is “How do you know this rock is from The Moon?” Well, that is what the Apollo returned samples made clear. I try to explain to the individual asking the question that moonrocks come from a place in the solar system where they have developed in a particular elemental signature. I try to tell them about how Moon rocks have acquired amounts and kinds of isotopes unlike the signature of rocks from other places in the solar system. That this signature is the same as that found in the rocks returned by the Apollo Astronauts. I can not go into much more detail with them, I frankly do not know enough about the laboratory processes involved to tell them too much more. I do know that the gases, often noble gases are extracted from the rocks and meteorites and that the sample is sent to a mass spectrometer or similar instrument to determine the composition and the ratios of the gases and their families of isotopes.

Today there are according to one source on the internet 371 Lunar meteorites. Some meteorites of this number are paired. Multiple samples of the same meteorite were classified by different laboratories so the actual sample of lunar material is from much fewer than 371 sites on The Moon. And many of the meteorites may have come from just a handful of huge events on our nearest neighbor. Still, the surface of The Moon is covered with thousands of craters, so it seems quite reasonable that the lunar meteorites represent samples from many locations distinct from the places the astronaut visited.

This is a whole individual of NWA 11273 that weighs 4.2 grams.

The actual mechanize for getting rocks off The Moon and to the Earth is giant impacts of asteroids into the lunar surface. During the cratering event, the material being blasted out of the forming crater needs to be accelerated to the escape velocity of The Moon. If this happens the boulders rocks and dust that make it off the surface will not fall back with the vast majority of the material thrown up from the impact. These escaping individuals will then travel around the sun in orbits until they fall to Earth to be found as meteorites. There has been much discussion about whether or not a particular type of impact is required to accelerate ejecta to escape velocity. One idea is that low angle impacts that plow masses of material in front of an impactor and which make elongated craters are the type with the possibility of accelerating the plowed material to escape velocity. The speed needed to leave The Moon is so much lower than what is required to leave a planet permanently, maybe more types of cratering events can create lunar meteorites. The great number of lunar meteorites, represents a tremendous opportunity to study The Moon since we are not going there presently to collect samples from additional locations.

I watched the Apollo 11 astronauts on The Moon and the other landings with great interest. I was already fascinated by meteorites and had been once to Meteor Crater and walked around its perimeter. I found a few pieces of iron shale, and cool rocks that day. I was reading all of H. H. Nininger’s books and had already sent him a piece of Mojave Desert basalt. I was disappointed that the missions stopped and remain disappointed 50 years later that we have still not returned to The Moon.

It is the nature of mankind to explore and seek to understand what is over the next hill or across the ocean and yes, across the vastness of space. No explorers of the past went to a place and collected a handful of rocks and said “Ok we have been here, this is what it is all like. We can return home there is nothing else to do or learn here.” If the explorers of the new world had come and said, “The new world is a swampy bug-infested place without gold and riches which the rulers of Europe seek.” then there would not have been the development of Florida and no Space Center there today. To not continue and explore further is against the nature of our species. Maybe that is what bothers me most. Even though I can not go into space and travel to The Moon there is a part of me that wants to go. And even more desires for someone to go in my place and to continue what was begun by the Apollo Astronauts. Thousands of us who grew up during the 1960s and 1970s thought as excited space geeks that we would be on Mars in a decade or two and looked to see tremendous new space challenges met and overcome in our lifetime. But it was not to be.

I loved the Space Shuttle. There is nothing more exciting than seeing a really enormous rocket burn thousands of pounds of propellant every few seconds and produce prodigious quantities of fire and smoke. But it is not the same (even with all the good work and knowledge it gave us) as going to The Moon or Mars or the asteroids. I still feel let down and I still yearn before the end of my life to see men and women walking on Mars and other places in our solar system. And I guess that should be enough soapbox preaching for one article.

I have had the pleasure to cut some massive lunar meteorites into slices and see more of the material from our natural satellite than most other people on Earth ever will. If the number of meteorite collectors in the world is a small number then the number of professional meteorite perparers is a vastly smaller number still. I have been thrilled with every tiny bit of metal that I have exposed with the blade in my slicing. Each just as exciting as the first. That tiny little flash of sparkle reminding me that asteroids and meteorites with nickel-iron have been incorporated into the moonrocks. I have been surprised by how solid and tough some of the lunar meteorites have been in the saw. Originally I thought that their pounded and crushed beginnings would leave them still somewhat friable but that was usually not the case.

This image is a table covered with slices from one of the smaller lunar meteorites (just 1.1 kilograms) I have been privileged to prepare in the last couple of years.
This is a full slice of the lunar meteorite NWA 11303. The slice weighs 9.047 grams.
The white spot is the brightly reflecting metal grain exposed by cutting in a lunar meteorite.

Back not too many years ago meteorite collectors bought lunar meteorites by the milligram. And we were thrilled to get a tiny piece of the newest small stone proven to be from The Moon. Things have changed somewhat. Several large finds of lunar meteorites have made it possible for collectors to acquire whole stones, endpieces, and slices weighing many grams. I posted to Facebook from the Kennedy Space Center images of the lunar rocks that I saw on the trip and was amazed at that moment by the fact that they were but 110-129 grams. I forgot for a second in the world of today with so many wonderful lunar meteorites how difficult it was to get the actual moon rocks the astronauts returned. Those astronauts may have been asked to look for diversity in the rocks they returned and diversity does not always come in big sizes. We experience this when hunting for meteorites here on Earth. Had those Apollo astronauts never accepted the danger and the challenge of the journey to The Moon we may never have been able to confirm with certainty that the lunar meteorites we love are from there as well.

This is an endpiece of the first lunar meteorite that I cut for the business. It turned out so nice and the 20 or so slices were so thin and polished so nice that Paul Harris and I decided that we would keep the endpieces for ourselves. Little did we know that in just a few months much larger stones would be found and the price would fall even farther. I like this 25.4-gram specimen.

In archeology, which with just a few different choices in life might have been my career, situation and context are everything for specimens. A specimen without context bought in an antique store reveals very little compared to a similar specimen recovered from a layer of dirt in the ground. As much as scientists can learn from lunar meteorites about the history of The Moon the returned moonrocks have whole added dimensions of knowledge to offer. Partly because they are uncontaminated, unweathered from exposure to the conditions here on Earth but in a bigger way because we know the exact location where they were picked up. When we hunt for meteorites in the desert we have two modes in which we often operate. One is we are looking for additional pieces of space rock where many have been found before. If that was a fall that was witnessed then there is just the one type stone and if it is a common type then the location of a piece I find is not so important and we may never share to the world all the collection information. A Holbrook found today is after all just one more of 20,000+ Holbrooks found. The other mode we operate in is cold hunting a spot where meteorites have never been found. Any find there is new and needs precise documentation for many reasons. Among these reasons are so the distribution of other pieces as they are found can be plotted to determine the rough confines of the strewnfield. Also, it is required that the location be provided if the newly discovered meteorite is to be classified and made official within the scientific community. Knowing just exactly where lunar rock specimens were collected provides many benefits to scientists studying the geology of The Moon.

This is a whole specimen of NWA 10203 a nice lunar meteorite of a paired group. It has relic fusion crust and just the beginning hints of the inside where it has eroded some. It weighs 1.5 grams.
The availability of meteorites from The Moon has offered me one other enjoyment that was impossible a few years ago. As I cut lunar meteorites I have the option to make some ridiculously thin slices that I can later make into thin sections. I enjoy grinding down and polishing meteorites until they are transparent and then photographing the structure of the stone under polarized light. Lunar meteorites are not very colorful as is often the case with other classifications of meteorites. Yet, even without the bright interference colors, they are fascinating in their own ways. The following is just one image of lunar meteorite NWA 11273 with polarized light.

I love just about everything about The Moon. I love to image it with my telescopes and cameras. I love the meteorites I have from there. I hope that I will see new astronauts return to The Moon and watch them learn to dwell there and then press on from The Moon to Mars.

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