Mysterious sounds in stratosphere can't be traced to any known source

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Solar-powered balloons floating 20 kilometres supra crushed person recorded inaudible low-frequency signals that person truthful acold not been traced backmost to immoderate known source

By Karmela Padavic-Callaghan

High up successful nan stratosphere, location are unusual sounds


Solar-powered balloons floating successful nan stratosphere person recorded low-frequency sounds of mysterious origin.

“When we started flying balloons years ago, we didn’t really cognize what we’d hear,” says Daniel Bowman astatine Sandia National Laboratories in New Mexico. “We learned really to place sounds from explosions, meteor crashes, aircraft, thunderstorms and cities. But virtually each clip we nonstop balloons up, we find sounds that we cannot identify.”

Bowman and his colleagues measured infrasound signals – sounds pinch a wave truthful debased they are inaudible to quality ears – utilizing solar-powered balloons floating 20 kilometres high.

The researchers built balloons astir 7 metres wide and made of bladed plastic. They filled nan balloons pinch charcoal powder, which heats up successful agleam sunlight and makes nan balloon float. Unlike upwind balloons, which emergence until they pop, these DIY solar-powered balloons coasted successful nan stratosphere for hours, carrying infrasound sensors complete hundreds of kilometres. The researchers deployed much than 50 balloons complete nan people of 7 years starting successful 2016.

The information they collected showed that nan stratosphere sounds rather different than nan aboveground of Earth. On nan ground, infrasound sensors prime up signals that person been deflected by winds connected their measurement down, but nan balloons floated supra those winds – they recorded signatures of turbulence successful different parts of nan atmosphere, and infrasonic sounds of marine storms. However, Bowman says that galore infrasound signals from nan stratosphere didn’t person an evident origin. He presented nan activity astatine a gathering of nan Acoustical Society of America successful Chicago, Illinois, connected 11 May.

These mysterious signals could beryllium related to types of atmospheric turbulence that person ne'er been recorded before, but infrasounds successful nan stratosphere person only seldom been explored earlier truthful it is difficult to make knowledgeable guesses, says Bowman.

The investigation squad inflating a star balloon pinch infrasound sensors attached

Darielle Dexheimer/Sandia National Laboratories

He says 1 of nan first balloon studies of this benignant was a US Army Air Forces research code-named Project Mogul, which sought to observe infrasound signals of atomic weapons tests successful nan Soviet Union successful nan 1940s. One of Project Mogul’s balloons collapsed successful Roswell, New Mexico, which brought nan apical concealed programme into nan nationalist eye. The cover-up to conceal nan balloon’s intent sparked UFO conspiracies, and astir of nan information from consequent balloon flights, ending successful nan 1960s, were kept classified, says Bowman.

Roger Waxler astatine nan University of Mississippi says he isn’t amazed by enigmatic infrasound signals appearing successful recordings of nan stratosphere. “On nan crushed you tin put sensors into arrays and cognize precisely wherever they are comparative to each other, which helps cipher wherever an infrasound came from. With balloons, they conscionable spell wherever they go,” he says.

Bowman is collaborating pinch NASA to create akin balloon exertion for an moreover little explored place: nan clouds of Venus. He and his colleagues want to accommodate their solar-powered balloons to grounds infrasound supra nan aboveground of Venus, which could thief chronicle nan planet’s seismic activity.