Equipped with rock picks and hand lenses, a team of geoscientists deployed to the Mojave Desert recently to investigate a tantalizing “fingerprint” detected by a NASA sensor. Their target: a cache of topaz hiding in plain sight.

The geologists weren’t searching for gem-grade treasure. Rather, the presence of topaz could hint at a more valuable deposit below of something known as porphyry copper.

One of the world’s primary sources of copper, these deposits are left behind when magma and hot water from deep underground course through Earth’s crust, chemically transforming the surrounding rock. This tends to occur where one tectonic plate dives below another, known as a subduction zone, such as the North American Cordillera, which stretches from the Canadian Rockies to western Mexico.

In addition to copper — the third most used metal in the world after steel and aluminum — the deposits can hold other critical minerals like molybdenum and tellurium, which are used in everything from steelmaking to solar panels. Finding the deposits isn’t easy. Geologists look for topaz because it forms under the same volcanic conditions.

For the team in the Mojave, the goal was to collect more evidence. That would require boots on the ground and a heavy bag of samples. The scientists who converged on the site included three experts from the U.S. Geological Survey (USGS) and Robert Green of NASA’s Jet Propulsion Laboratory in Southern California.

“What we’re doing out here is geologic CSI,” said Green, referring to the investigative TV show, as he split open a weathered red rock to expose a sparkling core. “We’re looking for clues to reconstruct what happened here.”

Next-generation mineral mapping

The sensor that detected the topaz deposit on public land near Barstow, California, was built at JPL. Called AVIRIS, short for Airborne Visible Infrared Imaging Spectrometer, it analyzes reflected sunlight and can be used to identify chemicals and minerals by their unique spectral fingerprint. The technology was pioneered in the early 1980s by a team that included Green, and space-hardened versions have explored the Moon, Mars, and other rocky bodies in the solar system in the decades since.

While its cousins study distant worlds aboard spacecraft, the AVIRIS line of sensors is advancing Earth science from aircraft. The latest model, AVIRIS-5, recently took to the skies for the first time as part of the NASA-USGS Geologic Earth Mapping Experiment (GEMx). The goal of GEMx is to identify sources of critical minerals across the American West, including in the waste rock of active and legacy mines. It is led by the USGS as part of its larger, nationwide initiative.

Since 2023, GEMx flights have covered more than 386,000 square miles (1 million square kilometers) of American soil, including most of California.

Ground-truthing the sensor data can entail hot field work, scrambling over steep crags to uncover samples for lab analysis. While testing has confirmed the topaz discovery, determining if the Mojave site overlies a porphyry copper deposit will require intensive investigation using ground-penetrating equipment. But the AVIRIS finding shows how advanced NASA airborne sensing can help lead geologists to the metaphorical needle in a haystack, even in heavily explored Southern California.

“People have been prospecting this area for generations,” said Erik Tharalson, a USGS geologist. “But there’s a lot more to discover.”

High flyer

From the beginning, the GEMx mineral mapping campaign has been enabled by one of the highest-flying aircraft in NASA’s fleet: the ER‑2. It deployed on March 31 from NASA’s Armstrong Flight Research Center in Edwards, California, to Colorado Springs Airport in Colorado.

“We deployed to Colorado Springs to maximize flight time for data collection needed in Colorado, Utah, New Mexico, Arizona, and Texas,” said John McGrath, ER‑2 project manager at NASA Armstrong.

By the conclusion of this deployment on June 5, the aircraft had completed 26 flights totaling more than 125 hours. Soaring at about 65,000 feet, the ER-2 can fly at high altitudes that allow it to collect broad‑area, high‑resolution spectral measurements in a single pass, supporting researchers studying mineral composition and surface processes.

In 2025, the aircraft flew 36 science missions, collecting more than 7 billion measurements over 200 flight hours. The data has contributed to the largest airborne surface mineralogy dataset gathered in a single NASA-USGS campaign.

The GEMx survey is led and funded by the USGS Earth Mapping Resources Initiative. Earth MRI is modernizing mapping the nation’s surface and subsurface to find new, critical, and other minerals. It is a partnership effort with 45 state geological surveys, federal agencies, private industry, tribes, universities, and others. The initiative will capitalize on both the technology developed by NASA for spectroscopic imaging, as well as the USGS expertise in analyzing the datasets, conducting field work, and deriving critical mineral information from them.

To learn more about GEMx visit:

https://science.nasa.gov/mission/gemx/

Media Contacts

Andrew Wang / Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-393-2433
andrew.wang@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

Written by Sally Younger

2026-037

Written by Catherine O’Connell-Cooper, APXS Strategic Planner and Payload Uplink/Downlink Lead, University of New Brunswick, Canada

Earth planning day: Friday, June 5th, 2026

In a very broad sense, Curiosity has two modes of doing science – one centred around a defined science campaign (such as the recent boxwork campaign) and the other as we move between campaigns. During a science campaign, with a very defined start and end location, every image and every workspace is carefully choregraphed to make sure we hit all of our science goals for the campaign. This is a lot of pressure!

But in between campaigns, the emphasis moves to driving towards the next major campaign. Our next major stop is the yardang unit, a series of intriguing wind sculpted, pale coloured hills which you can just see in the distance in the cover image for this blog. The rover planners (RPs) sometimes make our drives as long as they can and we drive as far as we can go, other times we stop a little short to look at interesting looking workspaces as we go. As part of the APXS team, I loved being part of the boxwork campaign and getting all the information we needed there …  but as a geologist, there is something very special about this kind of exploring, the sense of being a planetary explorer, ambling along to see what the rocks will show us.

So we continue southwards, trundling over laminated bedrock which varies from predominantly pale coloured laminated bedrock to bands with abundant thin flaky, darker coloured, layers and patches. Some of the rocks stick out at strange angles, which make planning drives more challenging. This past week there has been abundant dark layers interbedded with the more dominant pale coloured rock, both in place and in fragments around the workspace. APXS and MAHLI characterized some of this darker material, for example at “Rio Bio Bio” and “Placilla de Caracoles” and some of the paler material at the brushed targets “La Primavera” and “Los Quemados.” ChemCam also analyzed both types of rocks along the way.

We are busily acquiring Mastcam and ChemCam LD-RMI (“Long Distance Remote Micro Imager”) images of everything even remotely interesting – and there are lots and lots of cool features around here. The wide open landscape here allows us to image features from several different angles and distances, such as “Mira Flores,” a small erosional outlier seen from a distance in this image and closer up here. Another great example is the “Kimsa Chata” trough which shows some amazing sedimentary structures, which may help us to determine if this was a desert or a lake or maybe something in between, such as a desert with some water moving through.

The Environmental Theme Group continues to populate each plan with environmental monitoring activities. Activities varied from dust devil monitoring in Gale crater to looking at levels of dust in the skies overhead. The weekend drive is planned to take us further into that drive distance shown in the cover image, to an area where the contrast between dark and light bedrock is more pronounced, and just beyond that, to an area which looks very smooth, with no jutting out blocks. From where we sit today, its impossible to say what it is but that is the fun of exploring – who knows what we will find? Stay tuned to find out over the coming weeks. 

The post Curiosity Blog: Sols 4913-4919: Planetary explorers, freewheeling to the Yardang unit! appeared first on NASA Science.