Back in his cozy office lined with laden bookshelves and topographic maps, lead scientist Jonathan Glen spoke about the necessity of adaptability in fieldwork. The suddenness with which conditions could change, despite the team’s careful planning, was a common thread running through the Surprise Valley expedition, first when the researchers encountered technical issues two days ago and again today. But what was important was that the team pushed forward to fulfill their original purpose--“coming together to do great science,” as Jonathan had said--no matter what path they took. After spending the first half of the field session at Cedarville Airport, watching SIERRA collect magnetic data from the sky, a sudden change in plans finally gave me the chance to soil my hiking boots as I learned about how geoscientists gather data on the ground.

On the third day of our expedition to map underground faults and fractures in Surprise Valley using unmanned aerial systems (UAS), the team felt confident that the SIERRA UAS would have a successful flight. NASA engineers had just fitted SIERRA with a new fluxgate magnetometer, an instrument that allows them to correct for magnetic fields associated with the aircraft that could obscure readings from the subsurface structures they’re interested in mapping. Two nights ago, the team spent hours troubleshooting the old instrument, eventually realizing that it had been incorrectly calibrated. Luckily, an engineer from Geometrics, the manufacturers of SIERRA’s cesium vapor magnetometer, an instrument that measures magnetic field strength, drove up yesterday with a new fluxgate.

With SIERRA aloft, I followed Jonathan and Noah Athens, both from the U.S. Geological Survey, out to the field, where they would communicate with SIERRA while driving four-wheel all-terrain vehicles (ATVs). The aircraft would transmit flight parameter and magnetic data to radio receivers on the ATVs, which would then store the data onto a hard drive as a backup in case the computer on board the SIERRA failed or the aircraft crashed. Since following SIERRA’s flight along tightly spaced east-west lines would be unfeasible on ATVs, Jonathan and Noah planned to drive along a perpendicular north-south path, allowing at least one ATV to remain within range of the aircraft at all times.

Not long after Jonathan and Noah unloaded the ATVs, Jonathan received a call from the ground base station. Within minutes of takeoff, SIERRA began slowly losing magnetic data. Soon, the rate of data loss climbed, until the ground base station completely lost all signal from the fluxgate aboard the SIERRA. After landing the aircraft, they wheeled it to the hangar for troubleshooting.

“Wow,” Jonathan said as he hung up the phone. “There’s so much we could do today.” He rubbed his chin, gazing intently at the vast desert stretched out before us.

After a few seconds of pondering the possibilities, he decided that Noah and I would collect magnetic data by foot along a line they had plotted based on previous surveys that hinted at the presence of an underground fault or fracture in the area. Hopefully the ground-based survey would capture the subsurface feature, which should appear as a distinct magnetic pattern, or anomaly, in the data.

We would take magnetic readings with a magnetometer pack, a bulky instrument resembling a cross between a backpack and a lawn chair. A bulb-shaped GPS antenna and a cylindrical cesium vapor magnetometer protrude a few feet from the top of the backpack on either side. The frame is aluminum, which is non-magnetic, so as not to interfere with the magnetometer readings.

Jonathan hoisted the pack onto Noah’s back, tightening the straps and securing the magnetometer console, which stores and displays the data, snugly around his waist. Then Jonathan showed me how to use a handheld GPS to navigate our traverse, or the line along which we could collect data, which the team had programmed with the line’s endpoint. I transferred our cell phones, keys, and water canisters into a knapsack that I would carry while walking at least a hundred feet in front of Noah--far enough to prevent our magnetic, electronic belongings from interfering with the magnetometer readings. After double-checking that we had everything we needed, Jonathan drove off to rejoin the NASA engineers back at the airfield.

I wove my way through clumps of brittle sagebrush, breathing in their heady, medicinal aroma as I brushed against them. After nervously scaling a steep dune, I paused to look at the stretch of dry lakebed, or playa, below, and the hazy blue silhouette of the Warner Range far ahead. Then I made the slow, careful descent to the playa.

I continued walking, every now and then turning back to check on Noah and glancing down at the GPS to make sure I hadn’t veered off course. A few dull-hued rocks and animal bones occasionally interrupted the expanse of cracked, parched earth. Mirages of lakes rippled along the base of the mountains. After two miles, I reached the endpoint, where I stopped and waited for Noah. Without the steady tread of my footsteps, the desert was utterly silent, as if to remind me even more of its desolateness.

Once Noah caught up with me, we both stopped to drink water. We decided to trade duties. After fastening the magnetic pack onto my back, he quickly explained how to use the console. Then we turned around and made our way back to the start point.

The magnetometer pack hung heavily from my back, forcing me to lean forward awkwardly as I walked. Toward the end of our hike, I struggled to trudge through the length of soft playa near the foot of the dune. The weight of the pack pushed me over the other side of the dune, leaving me with little choice but to slide and hope I didn’t crash on the way down. Once I reached Noah, I immediately began unfastening the pack from my shoulders, anxious to relieve myself of its weight. I had ventured on this expedition anticipating refreshing, picturesque hikes through nature. I still stood in awe of the desert’s surreal beauty, but now with an undiluted, unromantic appreciation for the physicality of fieldwork and the researchers’ passion for doing science even in challenging conditions.

That evening, Noah opened up his laptop and showed me the magnetic data we had collected on the playa. The screen displayed the readings as a curve, its two halves mirror images of each other, representing our hike to and from the endpoint. A magnetic anomaly appeared as an undeniable peak emerging from each half. In other words, the researchers had successfully homed in on the subsurface feature they predicted to be located in the area. They would perform more of these ground surveys, collectively generating high-resolution mappings of geologically interesting regions.

Sometimes the team needed to respond to the unpredictable twists and turns of fieldwork with an equal measure of swift, yet purposeful, action. Even with SIERRA grounded, the team collectively adapted, continuing to map Surprise Valley’s subsurface. And now, reveling in my wrinkled, dirt-streaked clothes and the layer of grime on my freshly scraped skin, I could share somewhat in the satisfying exhaustion the team’s geoscientists experience following hours in the field, collecting data that in its own small, though significant, way, contributed to “great science.”

Image sources: 1, 2, 3

Previously in this series:

Mapping Underground Faults and Fractures in Surprise Valley

Surprise Valley: Smoothing out the Kinks

Surprise Valley: A Valley of Surprises