Away Team Mission: NASA, USGS Scientists Go Rock Hounding in California’s High Desert
Editor’s note: when it comes to conducting field trips – sorties – Away Team missions – on another world, astrogeology and astrobiology and astrochemistry overlap with one another all the time. The processes whereby humans and/or robots plan and then execute an examination of a planet’s surface focus on the peculiar aspects of the planet they are exploring – but they may also incorporate ample flexibility for the discovery of unexpected things. This includes sampling, photography, cartography, geodesy, and ad hoc – on the spot – decision making by the astronauts – and not necessarily with Mission Control on Earth looking over their shoulders. Using analogs on Earth – locations that replicate or mock one or more aspects expected to be encountered offworld – is a proven way to develop planned and unplanned exploration by astronauts. Sometimes astronauts do the exploring in person. When distance or inhospitable conditions prevent onsite astronaut sorties then robots can fill in the gap. Either way, humans are in the loop and practicing on Earth helps prepare them for the unknown.
The discovery of topaz on a volcanic outcrop in the Mojave Desert may hint at a porphyry copper deposit below.
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.
California’s high desert stretches below a bright spring sky in April 2026. NASA and USGS scientists are using airborne remote sensing to home in on potential sources of critical minerals here and across the Western U.S. Credit: NASA/JPL-Caltech
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.”
Three-dimensional image cubes illustrate the volume of data captured by NASA imaging spectrometers. The front face shows an aerial view of the Mojave Desert. The colorful side panels reveal what no eye or camera can detect: the spectral fingerprints of minerals present in every pixel. Credit: NASA/JPL-Caltech
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.
Astrobiology, Astrogeology,
