Phobos and Deimos

In Gulliver’s Travels, which was published 300 years ago today, Jonathan Swift wrote that the people of Laputa had made an important discovery: “two lesser stars, or satellites, which revolve about Mars.” The fictional moons were small and close to the surface, orbiting the Red Planet in a matter of hours. Earthly astronomers took a little longer to find the real moons – they weren’t discovered until 1877. They were named Phobos and Deimos – fear and panic – after attendants of the god of war. Phobos is the larger moon. It’s lumpy, with an average diameter of about 14 miles. It orbits just 3700 miles from the surface of Mars. It rises in the west, then sets in the east less than four-and-a-half hours later. Deimos is about eight miles in diameter. It’s about three times farther from Mars, so it takes about two-and-a-half days to cross the sky, from east to west. It’s shaped a bit like a potato with a big dimple on one side. Several spacecraft have flown past the moons. But they’ve raised a lot of questions about them. Now, 300 years after Gulliver’s Travels, scientists may take a big step toward finding some answers. Japan launched the Mars Moons Exploration mission this month. The craft will study both moons from close range. And it will touch down on Phobos, hoovering up a few grams of pebbles and dust for return to Earth. More about that tomorrow. Script by Damond Benningfield