2007-04-21 17:46:20 · 3 answers · asked by ashish b 1 in Science & Mathematics ➔ Astronomy & Space
The answer has to do with the much larger distance that Deimos is from Mars in its orbit around the red planet. Orbital speed is inversely proportional to the length of the semi-major axis of the orbit (which is the mean distance between the moon and the planet). Specifically, orbital speed for a circular orbit is inversely proportional to the square root of the radius of that orbit. Since the gravitational force is less at a greater distance, the orbital speed is less. Moreover, the distance around the orbit of Deimos (the circumference of that orbit) is more (again due to the greater distance from Mars), so it has much farther to travel to complete one orbit. This results in a much longer orbital period.
2007-04-21 18:27:01 · answer #1 · answered by Anonymous · 2⤊ 0⤋
Kepler's third law (the law of harmonies) and the fact that Phobos is closer to Mars than Deimos (Phobos at 9,380 Km from Mars, Deimos at 23,460 Km)
2007-04-22 07:50:16 · answer #2 · answered by stardom65 3 · 0⤊ 0⤋
The farther away a moon is, the farther it has to travel, and the slower it's going.
2007-04-22 20:27:14 · answer #3 · answered by Nomadd 7 · 0⤊ 0⤋