On the small island of Vulcano, off the coast of Sicily, a drone traces a slow arc through drifting sulfurous steam while a laser tracks it from the crater rim. The scene looks otherworldly, but its purpose is practical: to read the chemistry of a volcano's breath before it stirs.
A team from the Technical University of Munich (TUM), led by robotics researcher Achim Lilienthal, has built a system that measures volcanic gases from a safe distance. A laser mounted on a small, self-aiming cart locks onto a reflector carried by the drone. As the beam crosses the gas plume, part of it is absorbed – and from that faint dimming, the amount of carbon dioxide in the air can be calculated.
Thousands of readings, drawn into a map
Flying a preset route up to 60 metres away for 10 to 15 minutes, the drone gathers as many as 3,000 measurements. An algorithm, accounting for the local wind, turns them into a map of gas concentrations across the crater. In wind-tunnel tests the method proved accurate to within about five percent, according to the TUM group.
What the researchers are really after is a ratio. As magma pushes upward, it releases more gas, and the balance between carbon dioxide and sulfur dioxide shifts. Tracking that ratio can hint at rising pressure below the surface – an early signal that an eruption may be building.
A second German team, from Johannes Gutenberg University Mainz under chemist Thorsten Hoffmann, takes a different route, flying onboard sensors directly through the fumaroles – vents where gas escapes at 100 to 140 degrees Celsius. Their drone, nicknamed "Tina" and weighing just 2.5 kilograms, samples gases and particles from within the plume itself.
Keeping people out of the danger zone
The shared advantage is safety. Until now, such gas measurements often meant researchers walking into corrosive clouds in masks, or scaling summits that are unreachable on foot. A drone can slip into the diluted edges of a plume, change direction if the wind turns, and come back with data no person should have to collect in person.
Vulcano, whose last eruption came in the late 19th century, was a calm proving ground. Next, the teams plan to take their drones to Mount Etna, where a fresh eruption has just begun.