On the 50th anniversary of Apollo 11, The Times’s graphics, science, and immersive teams look back to Neil Armstrong’s first step and forward to humanity’s next big leaps.
Someday humans may inhabit the Moon; should this happen, it would be fitting for them to recognize Apollo 11’s landing site as a historic landmark.
Basalts
Basalt is one of the most widespread volcanic rocks on Earth and one of the most pervasive types of igneous rock found throughout our solar system. Generally composed of black to dark gray or nearly black rock with fine-grained textures caused by rapid cooling near or at Earth’s surface, basalt often contains large crystals known as phenocrysts within its fine-grained matrix and often boasts lower silica contents than most rock types, typically between 45-52% SiO2.
Basalt comes in many variations that differ by chemical composition. Common variations include MORB basalts (tholeiitic), alkali basalts and olivine-rich basalts; each variant has unique chemical features but all share similar properties.
Thaleiitic basalts are a type of basalt composed of high concentrations of iron and magnesium. Commonly found at ocean ridges or back-arc basins, Thaleiitic basalts often form during continental rifting or hotspot volcanism and often form large igneous provinces such as Deccan Traps in India or Siberian Traps in Russia.
Alkali basalts are characterized by high concentrations of alkali metals and reduced amounts of silica, typically seen erupted from hotspots or volcanic arcs during later stages of activity. Olivine-rich basalts typically feature higher alumina content than standard basalts and are most often produced at active volcanoes in the mid-ocean ridge system.
Leucite-rich basalts typically have lower silica concentrations compared to tholeiitic and alkali basalts, as well as less magnesium and more titanium content. Erupting from active volcanoes at back-arc basins, leucite-rich basalts have their own distinctive coloration from that found in pyroxene and magnetite deposits found within other types of basalt. They’re often referred to as seafloor basalts.
Breccias
The astronauts collected two main types of rocks from the lunar surface: basalts and breccias. Basalts are hardened lava while breccias are fragments of older rocks fused together. Armstrong and Aldrin, along with other Apollo missions, collected numerous lunar rock samples that demonstrated that maria and highlands on Earth are connected; their samples featured anorthosite rocks fractured apart by impacts over its 4.5 billion year existence before finally coming together again by impacts to create these striking rock samples from the lunar surface.
Breccias are typically formed of impact melt, with differing-sized clasts that form them. Clasts may be divided into textural categories, such as monomict or dilithologic; meteorites with only one type of lithology such as NWA 5000 and SaU 169 are examples of monomict breccias; in contrast, dilithologic breccias include two different kinds; NWA 7022 contains both anorthosite and mafic (dark, iron rich) crystallized impact melt.
Given the variety of petrographic thin- and thick-section methods that have been employed to classify meteorites, several petrologists have applied differing classifications of breccias found during Apollo missions that do not align. For example, their textural characteristics do not always fit with other forms of breccia.
Lunar meteorites are typically breccias, and many have come to be known as KREEPy due to high concentrations of radioactive elements like potassium, thorium and uranium.
KREEPy meteorites likely originate in or around Procellarum KREEP Terrane (PKT), commonly referred to as the lunar hot spot. PKT rocks exhibit intermediate FeO concentrations with high concentrations of rare earth elements (lanthanum and cerium) along with phosphorus concentrations. All sites selected for Apollo landings were in or nearby PKT.
Anorthosite
Anorthosite is a type of rock that is thought to have formed in the primitive lunar crust. Composed mainly of plagioclase feldspar – an abundant mineral on Earth – anorthosite forms when molten silicate minerals cool and solidify, creating this type of rock. Furthermore, anorthosite may be found among Earth’s layered igneous rocks as an example; for instance the ANT suite.
Gravitational differentiation may have played a part in anorthosite’s formation; lighter minerals floated to the top while heavier ones sank at the bottom of a magma ocean. Lunar anorthosite is one of the oldest lunar rocks and forms most of its highlands and crust.
Lunar anorthosite can be seen from Earth as bright-colored, highly reflective areas on the Moon known as lunar highlands. These ancient rocks covered much of its young surface before asteroids and comets began bombarding it. Anorthosite rocks brought back by Apollo astronauts have helped scientists gain more knowledge about its geologic history.
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Geologic Samples
Geologic samples are fragments of rock or soil that provide scientists with an indication of its chemical makeup in relation to its larger environment, including Earth’s Moon, Mars, and other planets. Geologists use samples taken from Earth’s Moon, Mars and other planets as indicators for billions of years of history and provide us with clues. Samples may also be taken for other purposes like testing for microorganisms in an area or understanding a geological process such as magma solidifying into rocks which eventually get buried by sedimentary rocks over time.
Armstrong and Aldrin collected two types of rocks during their Apollo 11 mission: basalts and breccias. Breccias provided clues as to the lunar history of magma flow and eruption, but basalts provided more significant insight. By dating them 3.6-3.9 billion years old, older basalts revealed evidence of hot molten magma oceans on the Moon that disproved an earlier theory suggesting it was mostly undifferentiated and cold.
Apollo 11 basalts contained significant quantities of titanium, an essential element for creating many metals used by humans, including those used in human medicine. This titanium was found in armalcolite mineral formation – named for Armstrong and Aldrin’s initials – which helps scientists better understand Moon history. These discoveries continue to aid scientific investigation of our lunar neighbor today.
Anorthosite evidence found in lunar breccias proved that its surface had once been covered in magma ocean, providing scientists with greater insight into its formation and evolution into what we see now as our lunar homeworld.
Apollo 11 samples have provided scientists with much to study, while also highlighting some of the risks involved with space exploration. One lesson from this mission is that we need to take equal precautions when protecting lunar sites as we do when protecting heritage sites on Earth such as pyramids or Everglades. Michelle Hanlon, an attorney specializing in space law who co-founded For All Moonkind has been working closely with members of Congress to draft legislation which ensures preservation of Apollo landing spots.