Mike Murray, age 10, of Dothan, Ala., for his question:

DOES MARS HAVE A MOON?

Mars, the only planet whose surface can be seen in detail from the earth, has two small moons or satellites. The closer and larger one, named Phobos, is about 5,800 miles from the center of Mars. The smaller moon is named Deimos and it is about 14,600 miles from Mars’ center.

Phobos has a diameter of about 14 miles at its equators and 11miles from pole to pole. Deimos has a diameter of about six miles.

Phobos travels around Mars once about every seven and a half hours while Deimos takes about 30 hours to make the circular trip.

An American astronomer named Asaph Hall discovered both satellites in 1877.

Mars is about four fifths as dense as the earth and its mass is only about a tenth that of the earth. Because of the planet’s smaller mass, its force of gravity is about three eighths as strong as the earth’s. A 100 pound person on the earth would weigh only about 38 pounds on Mars.