Sun-Powered Micro Flyers Could Unlock the Secrets of Earth’s “No-Fly Zone”

The mesosphere, a high-altitude layer of Earth’s atmosphere, is famously inaccessible to conventional aircraft—the air is far too thin to support flight. But scientists may have found a way around this limitation: tiny, ultra-light devices that rely solely on sunlight to stay airborne.

This innovation leverages a phenomenon called photophoresis, in which light causes gas to flow around an object. The effect is amplified in low-pressure environments like the mesosphere, which lies roughly 50 to 85 kilometers above Earth’s surface. In experiments replicating mesosphere conditions, these experimental aircraft successfully levitated, according to physicist Benjamin Schafer and his team in a recent Nature publication (Aug. 14). Their approach could shed light on this mysterious layer, often dubbed the “ignorosphere” due to how little we understand it.

Despite being just a centimeter wide and weighing under a milligram, the devices feel nearly weightless. Schafer, affiliated with Harvard University and the startup Rarefied Technologies in Albuquerque, N.M., describes them as so delicate that a simple breath could send one drifting away.

The design features two ultra-thin, perforated layers—resembling slices of Swiss cheese—stacked together. The top layer is transparent, letting sunlight through, while the bottom layer absorbs light. This temperature difference drives a flow of gas from top to bottom, generating lift and allowing the device to hover.

While similar concepts have been explored before, these new micro flyers produce the highest lift-to-weight ratio recorded for this kind of technology, Schafer notes. The team predicts that a device with a 3-centimeter radius could carry a payload of 10 milligrams, enough to perform basic measurements and relay data back to the ground.

Potential applications are exciting: these solar-powered fliers could measure wind speeds, temperatures, and pressures in the mesosphere—information that is otherwise very difficult to obtain. Beyond Earth, the technology might even be adapted to explore thin atmospheres like that of Mars.