Field Work 

Introduction: Terrestrial geologists frequently benefit from the opportunity to revisit field sites, minimal restrictions on sample mass, and access to high-resolution laboratory instruments. In contrast, lunar astronauts conducting fieldwork must be considerably more selective when choosing sampling locations and determining which samples to return. As NASA prepares for a crewed return to the lunar surface with Artemis III, the mission is expected to return approximately 25–83 kg of lunar material [1]. This range is lower than the sample masses returned by Apollo 16 and Apollo 17, and, if only the minimum threshold of 25 kg is collected, it may also be less than the sample returns from all other Apollo missions except Apollo 11 [2]. Given these mass constraints, NASA is soliciting proposals for human-deployed scientific payloads designed to assist astronauts in making informed, field-based decisions about which geological samples to return to Earth [3]. Careful selection of these instruments is essential to ensure that lunar astronauts can identify and return samples with the highest potential scientific value.

The selection of such payload instruments should prioritize scientific value, operational simplicity, durability, compactness, and clarity of data output [3, 4]. These instruments must also satisfy requirements related to technology readiness, mass and cost limitations, mission operations, minimal crew-time demands, and crew safety and human-factors considerations [3, 4]. Looking ahead to eventual crewed missions to Mars, communication delays between Earth and Mars introduce additional operational challenges, making real-time guidance from mission control impractical [5–6]. As a result, Mars explorers will need to operate with greater autonomy than lunar crews, relying on instruments capable of rapid in situ assessments and preliminary interpretations to guide fieldwork and sample selection.
My analog astronaut research investigated the practicality and feasibility of employing a portable gamma-ray spectrometer during simulated EVAs at the Mars Desert Research Station (MDRS) to inform and support future human planetary field operations.

Handheld Gamma-Ray Spectrometer Rationale: The handheld gamma-ray spectrometer was a last-minute addition, prompting a revised research strategy to accommodate its capabilities. The original plan centered on the use of a portable Raman spectrometer; however, three separate Raman units were found to be nonfunctional and could not be repaired within the remaining preparation time.  This pre-mission circumstance highlights the critical importance of assessing the durability, robustness, and reliability of handheld instruments intended for Artemis surface operations. Although portable Raman spectroscopy may become more technically mature prior to future Artemis landings, sustained development and rigorous testing will be essential to ensure its readiness for crewed missions. A handheld gamma-ray spectrometer would also provide valuable ground-truth measurements to complement orbital data for the Moon and Mars. Although orbital gamma-ray spectroscopy has greatly advanced our understanding of these bodies, no Apollo astronauts had access to a field-deployable instrument. Including such a spectrometer in future missions would improve astronauts’ ability to contextualize orbital observations and identify high-value samples.

Capabilities: Gamma-ray spectrometers provide rapid field assays of radioactive elements, enabling interpretation of lithology and geochemical conditions, indirect inferences about clay minerals, and assessment of potential human hazards such as radon exposure [7]. An RS-125 Gamma-Ray Spectrometer was used for this study, measuring 25.9 × 8.1 × 9.1 cm, weighing 2 kg, and featuring a rubberized grip, dust protection, single-button operation, and a sound output loud enough to be heard in MDRS spacesuit helmets over a blowing fan. The assay was conducted at a 120-second interval, reporting the weight percent of potassium (K) and the concentrations (ppm) of uranium (U) and thorium (Th). The data is displayed on the digital screen and saved directly on the instrument; however, the device does not include a GPS, so location information must be manually recorded.

Gamma-Ray Training: To effectively utilize the portable Gamma-ray spectrometer during field missions, the analog astronauts required minimal training and expertise. The operation of the portable gamma-ray spectrometer is straightforward, making it accessible for any analog astronaut. Therefore, less than 10 minutes of training is needed for basic usage. The primary challenge lies in choosing optimal geological formations and interpreting the results. Any lunar astronaut could be trained in preliminary interpretation since there are only three elements to consider.

Gamma-Ray Usage on EVA: The portable gamma-ray spectrometer is lightweight and imposes minimal impact on the payload capacity allocated for geological samples. Although bending or kneeling to position, read, and retrieve the device in an MDRS spacesuit may vary depending on terrain and local geological features, its compact size helps minimize physical strain during operation. Each assay requires approximately two minutes (adjustable), a duration that may be somewhat long for astronauts conducting multiple EVA tasks but remains reasonable for a field geologist making general assessments of geological units. The instrument is readily operable while wearing polyurethane-coated gloves, utilizing a simple one-button interface whose functions vary by press duration. Its compact, robust design enables effective use across uneven terrain, including while hiking, descending into dry streambeds, or withstanding minor impacts such as incidental contact with rocks.

Results from the Geological Region: The results from the Gamma-Ray on the regolith are summarized briefly, as the San Rafael Swell area around the MDRS has already been extensively analyzed and the primary focus of this study was on the practicality of the instrument. For results specifics on my trip please visit the MDRS Crew Reports for Crew 297 [7]. The spectrometer detected higher potassium levels in the red regolith compared to other regolith colors. Analysis of the Th/U ratio indicates that the red regolith is oxidized, consistent with field observations, and suggests that its red coloration likely results from iron oxide–stained clay minerals. Additionally, the Th/K ratio implies that the clay minerals present in many of the regolith are likely smectite.

Future Work: Future studies should directly compare portable field instruments, such as Raman, infrared (IR), and laser-induced breakdown spectroscopy (LIBS) systems, with handheld gamma-ray spectrometers to evaluate their relative durability, effectiveness, and overall utility in field conditions. Research could also explore integrating a gamma-ray spectrometer into a broader instrument suite rather than using it as a standalone device.  Additional testing is needed to determine the optimal assay duration and to assess the usability of instrument controls while wearing gloves more similar to what the future lunar and martian astronauts would wear. Testing in similar radiation, temperature, gravity, etc environments would also be needed to determine through space simulation testing.

Conclusion: The portable gamma-ray spectrometer enables real-time decision-making during EVAs, as it can distinguish between samples that appear visually similar but differ in radioactive trace element composition. Although the information it provides is more limited than that of other analytical tools, its advantages, particularly reliability, durability, and simplicity, appear to outweigh these constraints. Its consistent performance demonstrates that this type of instrument could serve as a practical and effective tool for astronauts during future lunar or Martian missions in some capacity. Overall, the gamma-ray spectrometer could be successfully used by astronauts with minimal instrumentation and geological training.

Acknowledgements: I thank the University of Kansas Graduate College and the Department of Geology for funding this work. I am grateful to Dr. Karin Goldberg for recommending the use of a gamma-ray spectrometer. I also thank the Kansas Geological Survey for providing access to their gamma-ray spectrometer for the two-week mission.

References: [1] NASA. (2020). Artemis III Science Definition Team Report: A Bold New Era of Human Discovery.  [2] Heiken et al. (1991) Lunar Sourcebook: A user’s guide to the Moon. [3] NSPIRES - NASA ROSES-24. F.12 Artemis IV Deployed Instruments. [4] Steigerwald, W. (2018). How NASA Goddard tests tools astronauts will use to explore distant worlds. NASA. [5] Cranford, N. & Turner, J. (2021). Step 3, Artemis: Moon missions as an astronaut testbed for Mars. NASA. [6] Rando, C. & Schuh, S. (2008). SAE International. [7] MDRS Crew 297 Reports (2024) Mars Society. 

As a requirement for my B.S. in Geology,  I was required to complete a field camp that lasted at least three weeks. Since my university didn’t offer a field camp at the time, I had to take one at another school. I came across a program at the South Dakota School of Mines offering a three-week camp in Ecuador (two weeks) and the Galápagos Islands (one week), focusing on volcanology.

Having grown up in Kansas and spent most of my education there, I became tired of studying and working with sedimentary rocks. My university didn’t offer volcanology, but I had always been fascinated by it, so I was determined to find a way to take this volcanology course. 

On top of that, I had never been out of the country, and I’d dreamed of visiting the Galápagos Islands since second grade when I first learned there were penguins there. I was amazed that penguins made the journey from Antarctica to the islands. Then, in seventh grade, we learned about Darwin’s trip and how he came up with the theory of evolution, which made me even more determined to go. This opportunity seemed like the perfect chance to combine my love for volcanology with my dream of seeing the Galápagos.

The first week of camp we characterized igneous rocks and made detailed stratigraphic columns of the stratovolcano Tungurahua in Ecuador. The next week we spent at Cotopaxi National Park, mapping the lava fields and making stratigraphic columns. The last week of field camp we characterized cinder cones and mapped lava tunnels in the Galápagos Islands.