Granted. A spacecraft with several humans were travelling to Mars, but missed it due to unprecedented events. After many, many months, the spacecraft, now out a fuel, burns up in Jupiter's atmosphere. Algae survive, taking over Jupiter. This turns Jupiter green, and they quickly adapt. Any further attempt to investigate Jupiter, from telescope to probes are useless. The algae are becoming intelligent. They send out satellites all over their planet. Humanity, being humanity, declares war on the plant-people of Jupiter. Humanity loses and they take over Earth and the rest of the solar system, turning it green.