On Earth, life occurs on land, in waters, underground and, researchers like Craig Venter have discovered through large-scale DNA analysis of air samples, including in the air. Even in Earth's relatively thin atmosphere, some bacteria species have only been found in the atmosphere. The earth has a solid bottom, but there are planets that consist only of gas: the gas giants. What would life look like on a Jupiter-like planet?
Researchers speculate that a gas giant could harbor floating life forms. When the gas giant's atmosphere is very dense, the life forms can move through the air like large flying wings. They may also look like huge balloons or, like some squid species, move with gusts of air (instead of water).
Astronomer Carl Sagan thought of three kinds of life forms: sinkers, which slowly whirl down and hopefully could reproduce themselves in time, balloon-shaped creatures and predatory flying creatures.