|
Mars Moon Doomed, Experts Say
It's a good thing Mars has two moons, because it will eventually lose one of them. That's the conclusion of scientists who have been watching the planet's two satellites. Like many other orbits in the solar system that are predicted to go astray, this event is expected to take place millions of years from now, but signs of the catastrophe are already evident.
The Martian moons were discovered in 1877 by the astronomer Asaph Hall. He named them Phobos and Deimos, after the chariot horses of Ares, the Greek god of war. (The Romans called him Mars.) Very tiny compared with Earth's moon, the two Martian satellites are shaped more like potatoes than the near-perfect orb of our own moon. That's because they are too small to have enough gravity to make them round.
Phobos (whose name means "fear" in Greek) is the larger of the two. Measuring 23 kilometers (14 miles) in diameter, it orbits Mars once every 7 hours. That gives Martian moongazers two chances to see it in a given day. Deimos (Greek for "panic") is about half the size of Phobos and it circles Mars once every 30 hours. Phobos passes closer to Mars than Deimos does. Its orbit is 6,000 kilometers (3,750 miles) above the Martian surface—too close for comfort. The planet is pulling
Phobos inward at a rate of 1.8 centimeters (0.7 inch) per year, and that rate is gradually increasing. If nothing can be done to reverse this—and clearly nothing can—in about 40 million years Phobos will either crash into Mars or be torn into pieces that would continue to orbit as a ring of debris.
|
|
