Hourglass Sea

StarDate: November 28, 2009

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Mars is pouring on the charm as we head toward the end of the year. Right now, the planet rises in late evening, and is high in the southwest at first light. It looks like a bright orange star, outshining all but a few other planets and stars. And as the next few weeks roll by, it'll rise earlier each night, and shine a little brighter.

Through a decent backyard telescope, you can make out several features on Mars. One of the most prominent is a dark patch that was first recorded on today's date in 1659.

Dutch astronomer Christiaan Huygens drew the feature after viewing it through his crude telescope. By watching it for several nights, he used it to estimate that Mars turns on its axis once every 24 hours -- the first good estimate of the length of a Martian day.

Because Huygens and others used this feature to time Mars's rotation, a later astronomer named it the Hourglass Sea. In fact, at first, many thought it was a sea. Later, it was thought to be a big patch of vegetation that grew and shrank with the seasons.

In 1877, the feature was given the name that's still used today: Syrtis Major. It's named for the Gulf of Sidra in northern Africa.

Orbiting spacecraft have shown that it's an extinct volcano that's hundreds of miles wide, but only a couple of miles high. Not much dust coats its rocky flanks, so they stand out from the orange plains that surround Syrtis Major -- the first feature ever mapped on the Red Planet.

Script by Damond Benningfield, Copyright 2009

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