Solar balloon

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A solar balloon is a balloon that is filled with air and gains buoyancy because of the air inside the balloon gets heated because of the sun's radiation; black balloon material is the most common way to heat the air inside the balloon. Due to the dark color of the balloon, it heats up in the sun. This causes the air present inside the solar balloon to expand and reduce in density compared with the surrounding air. As such, the balloon functions like a hot air balloon. Usage at the moment is currently predominately in the toy market, although it has been proposed that it be used in the investigation of planet Mars. Some solar balloons are large enough for human flight. A vent at the top can be opened to release hot air for descent and deflation.