Mars Equinox

StarDate: October 27, 2009

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Spring is getting started in the northern hemisphere today -- on the planet Mars. It's the vernal equinox -- the day the Sun crosses the equator from south to north. The entire planet will receive roughly equal amounts of daylight and darkness.

Just like here on Earth, it'll get warmer in the northern hemisphere and colder in the southern hemisphere as the Sun moves farther north in the sky. But on Mars, the effect is more exaggerated because the planet's orbit is more stretched out.

Earth's distance from the Sun varies by only about three million miles, so there's not a huge difference in the amount of solar energy we receive during the year.

But Mars's distance varies by about 26 million miles. Such a large swing means that Mars receives about a third less solar energy when it's farthest from the Sun than when it's closest. So there's a far larger swing in temperatures from season to season.

Mars is closest to the Sun when it's winter in the northern hemisphere and summer in the south. As a result, summer is much warmer in the southern hemisphere, and winter is much colder. The northern half of the planet is more temperate -- the place to live if you like moderate conditions year round.

Mars rises around midnight, and stands high in the south at first light. It looks like a bright orange star. Keep an eye on it as we head into our own northern winter in a couple of months, when the planet will shine at its brightest.

Script by Damond Benningfield, Copyright 2009

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