Voyager 1 spacecraft photograph of part of the planet Jupiter, with two of its moons in the foreground. The moons are Io (left) & Europa. Io is about 350,000 km above Jupiter's Great Red Spot; Europe is 600,000 km from Jupiter. Although both moons have the same brightness, Io is much redder in colour. The picture was recorded on 13 February 1979, when Voyager 1 was 20 million km (12.4 million miles) from Jupiter.