She and her team flew these drones while inside the crater to compare distant atmospheric measurements with those closer to the source. They also used traditional ground sampling techniques to collect CO2 directly from the gas vents of the volcano.
With their drone data, the researchers found concentrations 23% above typical atmospheric levels, indicating that despite measuring away from the source, the samples contained sufficient volcanic CO.2 that they could distinguish it in the data. After accounting for dilution, they confirmed the amount matched their ground samples, showing that drones can replace in-person collection.
The team also measured the amount of CO2 was composed of carbon-13, a slightly heavier version of the element, which has 13 neutrons instead of the usual 12. They found that Poás had a significantly higher carbon-13 content in 2019 compared to data collected just a week before the 2017 explosion. This is noteworthy, D’Arcy says, because it suggests that carbon-13 levels could deplete shortly before eruptions and increase during calmer times, which would be useful to track with future drone flights.
“Being able to use drones to sample these gases helps us get a sense of the mechanisms that could lead to an eruption — and do it in a safe way,” says Benjamin Jordan, a volcanologist at Brigham Young University-Hawaii who was not involved in the work.
Drones, however, have their own challenges: in Poás, D’Arcy’s team lost three. (One flew out of range and stopped responding to signals, and another’s rotor became entangled with its gas sampling device and crashed. A third, sent to locate the second , fell from the sky at random.) Yet the equipment is relatively easy to replace, its price being only a few thousand dollars, which is cheap by research standards. “The cost of a human life is infinite,” says Jordan. “By using drones, you eliminate that risk.”
Researchers may never stop exploring the interiors of volcanoes; it is undoubtedly dangerous, but the experience is unlike any other. “It’s very humbling,” says de Moor, who visits Poás about once a month. “An almost spiritual feeling because you don’t really feel like you belong in this place, in such a hostile environment.”
He imagines that one day volcanic drone technology might look like something out of a sci-fi movie: sophisticated, self-driving gadgets optimized to withstand the hellish conditions of Earth’s most violent eruptions. “And then,” de Moor said, “we’re going to learn a lot.”