A time capsule from the Moon, preserved for nearly 50 years, now reveals its secrets through quantitative compositional mapping.
For nearly 50 years, a slender column of lunar soil, known as core 73002, waited patiently in pristine storage. Collected by Apollo 17 astronauts in 1972, this sealed sample was a gift from the past to the future—a time capsule holding clues to lunar history, preserved for a generation of scientists with tools unimaginable during the Apollo era.
Its recent opening marks a new chapter in lunar science, bridging the gap between the Apollo legacy and the upcoming Artemis missions. This is the story of how scientists are using cutting-edge technology to perform a quantitative compositional mapping of this precious core, translating its ancient particles into a detailed story of the Moon's violent and dynamic past.
QEMSCAN (Quantitative Evaluation of Minerals by SCANing electron microscopy)
The effort to study this core is part of the Apollo Next Generation Sample Analysis (ANGSA) program, a forward-thinking initiative designed to function as a low-cost sample return mission 4 . NASA and its early advisors had the foresight to leave some Apollo samples unopened, anticipating that future technological advances would reveal their secrets. The ANGSA program is the culmination of that vision.
Apollo 17 astronauts collect the 73001/73002 double drive tube at the base of the South Massif 1 .
Sample remains sealed in pristine storage, awaiting future analytical capabilities.
ANGSA program initiates careful opening and analysis of pristine Apollo samples.
QEMSCAN analysis provides unprecedented detail about the core's composition 1 .
Location: Base of the South Massif, Taurus-Littrow Valley 1
Geological Context: "Light mantle deposit" interpreted as landslide material 1
Scientific Goals:
This work directly prepares the Artemis generation for what is to come, creating a "generational handoff from Apollo to Artemis" 4 .
To extract information from the 73002 core without destroying it, researchers turned to a powerful, non-destructive technique: Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN) 1 .
The remaining 25% of the 73002 core was impregnated with epoxy and sliced into a series of continuous, 30-micrometer-thin sections, capturing the full 18.4 cm length of the core 1 .
The QEMSCAN system uses a scanning electron microscope equipped with energy-dispersive X-ray spectrometry (EDS). It automatically scans the entire sample, taking millions of individual measurements.
At each measurement point, the EDS system detects the elements present. The software then matches this elemental signature to a known mineral, effectively identifying what mineral is at that specific spot.
The result is a detailed, high-resolution mineral phase map of the entire thin section. Specialized software processors can then isolate individual particles, group them by mineralogy, and track changes in composition and texture with depth 1 .
| Material / Tool | Function in the Experiment |
|---|---|
| Apollo 17 73002 Core | The pristine lunar regolith sample, a time capsule of landslide material from the South Massif 1 4 . |
| QEMSCAN System | An automated scanning electron microscope that performs rapid, non-destructive mineral identification across the entire sample 1 . |
| Electron Microprobe (EPMA) | Provides high-precision elemental composition of specific mineral grains identified by QEMSCAN 1 . |
| Continuous Thin Sections | Slices of the core mounted on slides, allowing for the analysis of the sample's original structure and depth-related changes 1 . |
One of the primary scientific goals of this study was to identify mineral and lithic fragments of non-lunar, meteoritic origin 1 .
The lunar surface has been bombarded by impacts for billions of years, and it is theoretically possible that fragments of the impactors could survive, especially if the impact was at a low velocity or an oblique angle 1 .
The results were surprising. The detailed elemental analysis revealed that all 33 clasts were of lunar origin 1 .
This suggests that any meteoritic component in this portion of the lunar regolith is not present in the form of large, recognizable lithic clasts.
While no meteoritic material was found, scientists discovered a different geological treasure: a group of clasts with highly magnesium-rich olivine compositions (Fo92.2-96.5) 1 .
Such forsterite-rich olivine is a significant find that can tell us about the earliest stages of lunar magma ocean crystallization and the formation of the Moon's mantle.
Beyond the hunt for meteorites, the QEMSCAN data allowed scientists to conduct a detailed "census" of the core's contents and see how the lunar soil changed from top to bottom.
The sample is dominated by pyroxene and plagioclase, consistent with non-mare (highland) material 1 .
| Mineral Group | Approximate Abundance | Geological Significance |
|---|---|---|
| Pyroxene | ~45% | A key rock-forming mineral, common in lunar basalts and highland rocks. |
| Plagioclase | ~40% | The main component of anorthosite, which forms the ancient lunar highlands. |
| Olivine | ~5% | Found in certain lunar mantle rocks and magnesium-rich basalts. |
| Glass & Agglutinates | Variable with depth | Indicates soil maturity and exposure to micrometeorite impacts. |
| Oxides & Sulfides | <5% | Accessory minerals that can provide information about volcanic conditions and space weathering. |
The power of having a continuous core sample is the ability to track how properties change with depth.
| Property | Trend from Top to Bottom | Scientific Interpretation |
|---|---|---|
| Glass & Agglutinates | Decreasing abundance with depth 1 | The upper soil is more "mature," having been exposed to more space weathering and micrometeorite impacts that create glass 1 . |
| Soil Maturity | Higher maturity at the top, lower at the bottom 1 | Confirms that the upper regolith layer has a longer exposure history at the surface. |
| Stratigraphy | No clear layering observed 1 | Supports the theory that the material was deposited in a single, mixing event like a landslide, homogenizing the layers 1 . |
| Particle Size | Variations observed, but no consistent trend | Suggests a complex depositional history or multiple source materials for the landslide. |
Visual representation of how regolith maturity decreases with depth in core 73002 1
The quantitative compositional mapping of Apollo 17's core 73002 is more than a technical achievement; it is a profound link between lunar exploration's past and future.
Validated the landslide origin of the South Massif material and provided a detailed record of how lunar soils mature over time.
Uncovered clues about the Moon's magnesium-rich interior through the discovery of forsterite-rich olivine 1 .
The greatest success of the ANGSA program may be its demonstration that the Apollo samples, explored with new eyes and new tools, still have revolutionary stories to tell. As we stand on the cusp of returning humans to the Moon with Artemis, these findings remind us that the pioneering work of the Apollo era continues to light the way.
The unopened core was a promise from the past, and now, it has delivered, ensuring the Artemis generation is ready for the new lunar secrets that await discovery.