Washington, Sep 17: NASA's Juno spacecraft has beamed back an image of a long, brown oval known as a "brown barge" -- an elusive atmospheric feature in Jupiter's South Equatorial Belt.

Brown barges are cyclonic regions that usually lie within Jupiter's dark North Equatorial Belt, although they are sometimes found in the similarly dark South Equatorial Belt as well.

They can often be difficult to detect visually because their colour blends in with the dark surroundings. At other times, the dark belt material recedes, creating a lighter-coloured background against which the brown barge is more conspicuous.

Brown barges usually dissipate after the entire cloud belt undergoes an upheaval and reorganises itself. Juno is giving us the first glimpses of the detailed structure within such a barge, NASA said in a statement.

The image was taken earlier this month as the spacecraft performed its 15th close flyby of Jupiter. At the time, Juno was 11,950 kilometres from the planet's cloud tops, above a southern latitude of approximately 22 degrees. Citizen scientist Kevin M Gill created the image using data from the spacecraft's JunoCam imager, NASA said.