Aerobots (robotic balloons) may significantly change the future of in situ planetary exploration. On Venus, aerobots may serve as the scientific platforms for the in situ measurement of atmospheric gases and for the study of atmospheric circulation. They can be used to drop imaging and deep sounding probes at sites of interest and to acquire and relay high-rate imaging data. Balloon technology is enabling for any Venus surface sample return mission because of the need to lift the sample above most of the atmosphere for rocket return to Earth or Venus orbit. On Mars, aerobots can fill the gap in imaging resolution/coverage between the orbiters and rovers, and perform investigation involving atmospheric sampling, atmospheric circulation, magnetic field mapping and subsurface radar sounding. Solar-heated balloons could be used as low atmospheric decelerators for low-speed landing. On Titan, powered aerobots or even passive balloons can perform long duration low-altitude flight for surface mapping, in situ atmospheric measurements, periodic in situ surface sampling and deployment of surface packages.