The Planet Quiz Show

Jupiter completes one rotation in 9 hours, 55 minutes, 30 seconds.

This question is designed to help students associate the rotational period of a planet with the length of its day. In most instances a day is a very close approximation to the planet’s rotational period, unless a planet’s spin interval is a sizable fraction of its orbital period. Mercury and Venus possess such characteristics. Mercury rotates once in 58.6 days and revolves in 88 days, while Venus completes one rotation in 243 days and circles the sun in a period of 225 days. As a result, the time interval from one sunrise to the next sunrise on Mercury equals 176 Earth days. On Venus a day is shorter, 116.8 Earth days because Venus rotates in the opposite direction from most planets, including the Earth. If the sun could be seen on Venus, it would rise in the west and set in the east. The Earth rotates in a period of 23 hours, 56 minutes, 4 seconds, but as we all know one day equals exactly 24 hours. That is because we keep time by monitoring the sun’s position in the sky. It takes on average 24 hours for the Earth’s rotation to return the sun to the same position in the sky.

Jupiter's moon Europa is seen at the right, casting its shadow onto Jupiter's cloud tops. Scientists believe Europa possesses a thin warm layer of liquid water beneath its surface and has one of the best chances for supporting life in our solar system. NASA/JPL photo...