Why a 50-Year-Old Moon Rock Still Matters
The Apollo 17 mission of 1972 represents a high-water mark in lunar exploration. It was the final crewed journey to the Moon, but in many ways, it was just the beginning. Astronaut Harrison "Jack" Schmitt, the first and only professional geologist to walk on the lunar surface, and Commander Gene Cernan collected a precious geological library—110.5 kilograms of rocks and soil 4 .
Among the most intriguing of these samples was a "double drive tube" known as 73001/73002, collected at the base of the South Massif. For nearly five decades, a portion of this core remained unopened, a pristine time capsule saved for a future generation with more advanced technology 1 5 .
The unopened Apollo samples were more than just a curiosity; they were a strategic investment. NASA and its advisors in the 1970s had the foresight to preserve certain samples under special conditions, anticipating that future scientific instruments would be capable of extracting far more information 5 .
The Apollo Next Generation Sample Analysis (ANGSA) Program was initiated to finally examine these pristine samples as a low-cost "new" sample return mission, designed specifically to prepare for NASA's upcoming Artemis Program 3 5 .
ANGSA Program
A generational handoff where most of the 90+ scientists, engineers, and curators involved were not even alive during the Apollo Program .
Landslide Deposit
The 73002 core captured material from the South Massif that slid down to the valley floor, providing access to lunar highland material 1 .
The Digital Geologist: How QEMSCAN Maps Lunar Secrets
At the heart of this investigation is a powerful technology called QEMSCAN (Quantitative Evaluation of Minerals by SCANing electron microscopy). Think of it as a super-powered, digital geologist that never sleeps 1 .
Step-by-Step Journey Through the Experiment
1. Pristine Preparation
The 73002 core was carefully impregnated with epoxy and sliced into a series of continuous thin sections, capturing the entire 18.4 cm length of the core sample 1 .
2. Automated Scanning
The thin sections were placed in the QEMSCAN instrument which uses a scanning electron microscope (SEM) to systematically raster across the sample 1 .
3. Elemental Fingerprinting
At each point, the instrument fires electrons, causing the material to emit X-rays unique to the chemical elements present (energy-dispersive X-ray spectrometry) 1 .
4. Mineral Identification
The system's software analyzes elemental signatures and compares them to a database of known minerals, creating detailed mineralogical maps 1 .
5. Data Extraction
Specialized processors isolate and analyze individual particles, allowing scientists to count them, measure their size, and determine their mineralogy automatically 1 .
Essential Tools for Modern Lunar Geoscience
Gas Extraction Manifold
Extracts and analyzes gases sealed inside lunar sample containers for 50 years 5 .
Surprising Discoveries from the Lunar Landslide
The primary goal of the QEMSCAN analysis was to hunt for fragments of non-lunar meteorites—pieces of asteroids that bombarded the Moon and survived the impact 1 . The initial automated search was promising, flagging 232 clasts of potential interest based on their mineralogy 1 .
However, when the team performed more detailed chemical analysis on 33 of these clasts using an electron microprobe, they made a surprising discovery: all of them were of lunar origin 1 . This suggests that any meteoritic component in this part of the regolith is not present in the form of large, recognizable rock fragments, but is likely finely dispersed within the soil.
232
Clasts flagged for analysis
In the process of this meticulous search, the team uncovered other, more unexpected treasures. They identified a unique group of clasts characterized by highly magnesium-rich olivine compositions (Fo92.2–96.5) 1 . On Earth, such magnesium-rich olivine is often found in the mantle. Its presence in the lunar landslide sample provides a tantalizing clue about the deep lunar crust or upper mantle material that may have been excavated by the giant impact that formed the Serenitatis basin 1 4 .
How Lunar Soil Maturity Changes with Depth in Core 73002
| Depth from Top of Core | Key Observation | Scientific Interpretation |
|---|---|---|
| Upper Portion (0–~9.5 cm) | Higher abundance of glass and agglutinates 1 | Soil is more "mature," having been exposed to more space weathering at the surface 1 |
| Deeper Portion (~9.5–18.4 cm) | Lower abundance of glass and agglutinates 1 | Soil is less "immature," having been shielded from weathering and representing fresher landslide material 1 |
Soil Maturity
Refers to how long regolith has been exposed to the space environment (solar wind, micrometeorite impacts).
Stratigraphic Record
The landslide buried less mature soil under more mature surface soil, preserving a record of the event.
A Geological Story 4 Billion Years in the Making
The findings from Core 73002 help piece together a dramatic geological history for the Taurus-Littrow valley. The norites, troctolites, and dunites found in the region are ancient rocks, formed between 4.2 and 4.5 billion years ago as the Moon's original magma ocean solidified 4 . These rocks were later buried deep within the lunar crust.
The monumental impact that formed the Serenitatis basin blasted this deep-seated material upward, scattering it across the emerging landscape. The mountains of the Taurus-Littrow valley were sculpted by this and subsequent cosmic collisions. The landslide that deposited the material sampled by the 73002 core was a more recent, albeit still ancient, event that transported this jumbled geological record down the South Massif to the valley floor 1 4 .
4.5B
Years of lunar history
Key Rock Types Identified in Apollo 17 Samples
| Rock Type | Primary Minerals | Origin and Significance |
|---|---|---|
| Basalt | Plagioclase, Pyroxene, Ilmenite 4 | Formed from lava flows filling the valley floor 3.7-3.8 billion years ago 4 |
| Impact Melt Breccia | Rock and mineral fragments in a melted matrix 4 | Created by the immense heat and pressure of basin-forming impacts (Serenitatis, Imbrium) 4 |
| Troctolite (e.g., sample 76535) | Plagioclase, Olivine 4 | A deep crustal rock, a remnant of the Moon's earliest geologic history 4 |
The lack of clear stratigraphy in the core, dominated instead by a mix of non-mare (highland) material, is itself a key piece of evidence, perfectly consistent with the chaotic jumbling expected from a landslide 1 .
The Bridge to Artemis: A New Generation of Lunar Explorers
The analysis of Core 73002 is more than a historical postscript; it is a vital bridge to the future. The techniques and expertise honed during the ANGSA program are directly applicable to the Artemis Program, which aims to return humans to the Moon and bring back new samples 5 .
ANGSA Achievements
- First to open a core sample sealed on the lunar surface
- First to extract and analyze lunar gases
- First to process pristine Apollo samples in a cold glovebox
Artemis Connection
These capabilities ensure that when the first Artemis samples are returned from the lunar South Pole, the "Artemis generation" of scientists will be ready to handle them, analyze them, and extract the maximum amount of science.
The enduring scientific value of the Apollo samples, preserved and now re-analyzed with 21st-century technology, underscores the profound wisdom of saving them for the future. As we prepare to once again leave our footprints on the lunar surface, these ancient rocks continue to reveal new stories, proving that the greatest discoveries often come from looking at old secrets with new eyes.