European Space Agency scientists used interferometry on the International Space Station to make vapor above evaporating liquid films visible for the first time. The technique reveals wavy bands that trace concentration levels rather than height, turning an invisible cloud into a traceable pattern.

The Marangoni effect, a surface‑tension driven flow first observed by James Thomson in the 19th century, shapes the internal motion of evaporating liquids. On Earth gravity flattens both liquid and vapor, masking these subtle motions.

ESA’s Marangoni in Films experiment introduced a volatile, non‑flammable liquid to the station to study how evaporating films behave in microgravity. By observing the liquid and its vapor simultaneously, researchers can examine how the films organize and transport heat and mass. The findings are expected to improve cooling technologies, coating and printing processes, distillation and chemical engineering on Earth.

Additional experimental runs are scheduled in the Heat Transfer Host 2 facility during the summer, and the European Columbus laboratory continues to explore fluid behavior that defies gravity.