“A reasonable pilot, reviewing the chaotic wandering of my route across the country, would wonder what madness drove [me] to follow such an inefficient and irrational line,” writes aviator and geology and geophysics professor Gabe Bowen. “Perhaps they would assume that the route was cluttered with…an army of thunderheads…forcing a tentative hunt and retreat as gaps teased and collapsed in my path. I doubt that in a thousand guesses they would deduce my true cause.”

Over 10 days in March, Bowen and his 1961 Cessna (nicknamed 76X after its tail number) flew from Salt Lake City over the Great Plains to the Deep South, then down and through Florida and Texas and west to California before returning home. Along the way, they touched down at 82 airports, collecting a small sample of well water at each one. The samples have meaning beyond just scientific inquiry: Bowen hopes that his expedition might someday help bring home the unidentified remains of American soldiers, including prisoners of war.

It all starts with isotopes. Isotopes are different versions of the same element, give or take a neutron. That small difference in the weight of an atom is enough to affect the balance between heavy and light isotopes in a process like, say, evaporation. Lighter isotopes of hydrogen and oxygen rise into the water vapor while heavier isotopes get left behind.

Because of these processes, the isotope ratio of water varies from place to place. And that unique local isotopic signature is a part of us all. As our teeth, bones, fingernails and hair grow, the water we drink and the isotopic signature it contains is locked in—a snapshot of where we were at that point in time.

That means you are your own travelogue. Your teeth can tell you where you lived when you were a young child. Your bones, likewise, where you were in the last 10 to 20 years. And your hair can tell where you were in the past few months.

So if an American soldier dies overseas and can’t be identified through traditional methods, isotopes provide an additional tool: The soldier’s bones still contain a record of where they lived. If you can get a hometown, you’re much more likely to find a positive ID. Isotopes can bring a prisoner of war home.

That is, of course, if you have a complete, detailed map of isotopes in drinking water—much of which comes from aquifers below the ground—all over the U.S. So far, we don’t, but Bowen’s flight filled in 82 gaps.

It was more about just sample-gathering, however. Bowen admits that there are easier ways to gather groundwater samples. But those ways, he says, don’t give you the same context as traveling there yourself. Throughout his trip, Bowen saw firsthand how humans have shaped and utilized water systems across the country, and how differences in water affect people’s lives.

“Flying several thousand feet above the earth’s surface all the way across the country you really see how much water shapes the land,” Bowen says. “Sometimes it’s very obvious, sometimes you don’t see any water at all but you know it’s there.”

He wrote about his experiences in a project blog. You can read the whole thing here. But here are a few highlights:

“Leaving Salt Lake, I am able to climb through some wispy layers without trouble. The shimmer of crystalline ice particles surrounds me as I punch through the clouds. Some of these find their way through the porous shell of my 50+ year old airplane, appearing in the cockpit as a sparse but festive flurry of glitter. Paradoxically, these ice clouds signal no danger…frozen water will not adhere to an airplane.” – March 9, Salt Lake City to Western Kansas

“After two days of travel over landscapes where liquid water was passed from the sloping terrain like a hot potato, I now seem to have arrived at a place resigned to accept its fate as the loser of this game. The airfield elevations attest to the land’s limited energy to participate. Differences are measured in tens of feet and the water pools readily across saturated fields and farms between the high points.” – March 11, Fayetteville, Arkansas to Chattanooga, Tennesse.

“Now this [the U.S.-Mexico border] is what a homebound geographer must imagine a border to be, as if a giant with a pen and straight edge traced the image from the atlas with perfect precision. A thin streak; from my perspective it seems absurd that this feature could stop anything from moving across the vast expanse of desert below, but the intent of separation is clear.” – March 18, El Paso, Texas to Paso Robles, California

“As I cross the runway threshold, a current lofts 76X upward, reversing our descent in slow motion. We momentarily hang in the air, and then abruptly the air seems to be gone from under our wings. We plummet downward. I yank at the yoke to arrest our descent, though its effect seems only to minutely lessen the jarring thunk of our impact with the pavement.” – March 18, El Paso, Texas to Paso Robles, California.

His travels are filled, too, with stories. An airport manager in Colorado who refused to participate in the study. A chance encounter with the University of Arkansas women’s basketball team, coming home from the conference championship. Navigating through swarms of flight students in Florida. Returning with 76X to Georgia, where it was first delivered after being built. A bumpy ride over California mountains.

“I gather up the 82 bottles that constitute the tangible product of this adventure,” Bowen writes at the end of his blog. “They all fit in a box that could not hold a volume of maps describing the ground I’ve covered. Yet we will take them to the lab, and the information they reveal will help us draw maps depicting new dimensions of these landscapes.” The map will hopefully be ready, he says, in the next four to five years.

“After all,” he concludes, “we learned to fly, to tame the rivers, and to pull water from the ground where none appears to exist. We’re beginning to learn to deal with the impact of these activities. With a little ingenuity, some dedication and hard work, what’s to stop us from figuring this out?”

**Banner image: The full set of samples collected over Gabe Bowen’s 10-day journey.