Which one of the following planets does not have a satellite?
2016
Which one of the following planets does not have a satellite?
- A.
Earth
- B.
Mars
- C.
Jupiter
- D.
Mercury
Attempted by 4 students.
Show answer & explanation
Correct answer: D
A natural satellite (moon) is a celestial body that orbits a planet under the planet's gravity. Not every planet in the solar system has one — the number of natural satellites a planet holds varies from zero to hundreds, depending on the planet's mass, its distance from the Sun, and its orbital history.
For the planets listed here, the confirmed number of natural satellites is:
Planet | Number of Moons |
|---|---|
Earth | 1 (the Moon) |
Mars | 2 (Phobos and Deimos) |
Jupiter | Many (a large system, including the four Galilean moons) |
Mercury | 0 |
Mercury has no known natural satellite; its closeness to the Sun, weak gravitational pull, and narrow region of stable orbits (its Hill sphere) are the dynamical factors usually cited for why it has never been observed to hold one. This sets it apart from Earth, Mars, and Jupiter, each of which does carry one or more moons.
Hence, among the planets listed, Mercury is the one that does not have a satellite.