This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Pack your space bags and get in the spacetime capsule: we're going back to the Moon Landing! It's been fifty years since the first human set foot on unearthly soil. Apollo 11's success launched a series of missions that changed our understanding of our nearest neighbor, and we're going to celebrate this happy anniversary by exploring the geology of those incredible missions.
You can view the restored footage of that historic moonwalk courtesy of NASA. Humans have done a lot of remarkable things, but few will ever top this moment in history, when we naked apes built machines to launch ourselves off our own planet and land on another world. There's no air to breathe, or water to drink, but there are plenty of amazing rocks underfoot, and plenty of incredible sights to see under those black skies.
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That first moonwalk ushered in a dramatic new era of scientific exploration. Geology would no longer be confined to Earth. And the things we discovered were truly wonderful - and sometimes surprisingly familiar.
Rosetta Stones: Marvels and Mysteries of the Moon
3.6 billion year-old vesicular basalt sample, brought back from the Moon by the Apollo 11 astronauts. Credit: Mitch Ames Wikimedia (CC BY-SA 4.0)
People don't think of the stars when they think of geology – I mean, it's all about Earth, right there in the name. But the earth is made of star stuff. And the way gravity works, it turns that star stuff into rocky little worlds all over the universe, perfectly suited for our good science of rock-breaking. Geology isn't limited to the planet it was born on and named for. And we can take it all over space and time.
One of the first places we took it was our own moon. John Glenn is among the people who got us there: without his pioneering flight, without the early successes of astronauts like him (not to mention the legion of scientists, engineers, and computing women behind him), there would have been no Moon landing.
We got there. We grabbed some rocks. We made some nifty discoveries. And believe me, green cheese might be a pretty tasty substance, but it's nowhere near as delicious as the things the moon is actually made of.
Anorthosite is a fascinating rock and sparks interest even among those who usually don’t care about rocks. The reason is simple. Anorthosite is often composed of mineral labradorite which is famous for an iridescent effect called labradorescence. You’ll find more in this article: anorthosite and labradorescence.
The Moon highlands seem to be composed of anorthosite. We have both indirect and direct evidence for that. Measurements made recently by the Japanese lunar orbiter SELENE suggest that the lunar anorthosite may in many cases be almost totally monomineralic — composed entirely of plagioclase with very high calcium content. We have direct evidence also — American astronauts who visited Moon in the early 1970s brought back 61 rock samples that were found to be anorthosites.
EOS: Apollo’s Legacy: 50 Years of Lunar Geology
3.3 billion year-old lunar olivine basalt, collected by Apollo 15 astronauts. Credit: Wknight94 Wikimedia (CC BY-SA 3.0)
The earliest looks at the Apollo samples proved for the first time some facts about the Moon that may seem obvious today: There is not now and there likely never has been life on the Moon, meteor impacts throughout the Moon’s history have pulverized the surface, and the Moon and Earth share many geochemical similarities.
But technology, computer power, and scientific knowledge have grown exponentially since humans last stepped foot on the Moon in 1972. Thanks to the foresight of NASA leaders of the time, some of the Apollo samples were curated so that future scientists could study pieces of the Moon that hadn’t been exposed to Earth’s atmosphere.
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As post-Apollo scientists studied carefully doled out lunar samples, they discovered much more about the Moon and its history than scientists of the 1970s could have. Here are some of the most notable discoveries about our celestial neighbor that have come from Apollo samples over the past 50 years.
The Planetary Society: How the Apollo missions transformed our understanding of the Moon’s origin
For decades, the consensus of the planetary science community has been that the GIH [Giant Impact Hypothesis] is the best model to explain the formation of the Moon and account for its properties. While scientific literature on evidences for the GIH are varied in nature, in this article we focus on the Apollo missions. The Apollo missions represent a crucial dataset because they allowed us to test long-standing hypotheses using multiple in situ measurements, thanks to hundreds of kilograms of samples that were brought back to Earth.
Data from the Apollo landings show that the Moon’s formation isn’t as simple as we first thought. The results have been difficult to reconcile and interpret. Let’s examine how the Apollo missions changed our understanding of the GIH.
Georneys: Monday Geology Picture: Lunar Sampling Bag
Harrison H. Schmitt inspects an enormous boulder during the Apollo 17 mission. Credit: NASA
Bags such as this one were used to collect rocks during the Apollo missions to the moon. This particular bag even went to the moon’s surface in 1971 during the Apollo 15 mission. How neat is that!
NASA Earth Observatory Notes from the Field: The Footsteps of Apollo Astronauts
On our team’s last day at Kilbourne Hole, we were joined by retired astronaut Harrison “Jack” Schmitt, the lunar module pilot for Apollo 17. He is the only professional geologist to have walked on the Moon and is still an active researcher.
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The landing site for Apollo 17 was the Taurus-Littrow valley, a geologically intriguing area selected so that astronauts could collect samples of ancient rocks from the lunar highlands and look for evidence of young volcanic activity. There, Schmitt collected the “most interesting sample returned from the Moon.” It’s a rock known as sample #76535, which was collected as part of the rake sample at Station 6, located on the North Massif. Like the xenoliths we searched for at Kilbourne Hole, sample #76535 is olivine-rich. It’s a very old specimen that had not been damaged by shock events, and its origin is still being debated.
And finally, because no lunar landing story is complete without the howls of folks who believe the whole thing was a hoax, let us discuss how we can know it actually happened:
National Space Centre: How Do We Know The Moon Landing Really Happened?
Many of us either remember watching the landing ourselves or have heard the memories from our parents and grandparents. But what do you say when someone insists that the Moon landings never really happened?
In this blog, we dig into some of the common questions around the Moon landings, and address the more curious lunar phenomena with the latest data and scientific understanding. A vast weight of evidence supports the fact that humans really did land on the Moon multiple times between 1969 and 1972. But it is important to question and think critically about events of this scale – and sometimes researching and puzzling out the answers can be half the fun!
And who could pass up the opportunity to watch the Mythbusters bust the moon landing hoax myth again?