To determine which statement about Mars’ moons, Phobos and Deimos, is false, let’s take a closer look at each option:
- a) Both are in retrograde orbits: This statement is true. Both Martian moons orbit Mars in a direction opposite to the planet’s rotation, which means they are in retrograde orbits.
- b) Phobos is larger than Deimos: This statement is false. In fact, Phobos is the larger of the two moons, while Deimos is smaller.
- c) Phobos revolves around Mars in less than a Martian day: This is true. Phobos has an orbital period of about 7.6 hours, which is less than a Martian day (24.6 hours).
- d) Both are probably captured asteroids: This is also considered true. It is believed that both Phobos and Deimos originated as asteroids and were captured by Mars’ gravity.
- e) Both are very dark heavily cratered bodies: This statement is true as well. Both moons have dark surfaces and are covered with craters, indicating their age and lack of geological activity.
In conclusion, the false statement is b) Phobos is larger than Deimos.