Mars Closest to Earth This Week; Best View Until 2016

December 18, 2007

The bright yellowish-orange "star" poised above the constellation Gemini is actually the planet Mars, and this week the icy world is making its closest approach to Earth until 2016.

Earth passes Mars every 26 months, overtaking it in an "orbital race" as both bodies go around the sun. (Explore planetary orbits using an interactive solar system.)

"Earth comes close to Mars because our planet is moving faster in its orbit, catching up to and passing Mars," said Jaymie Mark Matthews, an astronomer at Canada's University of British Columbia.

This week's passage happens while Mars is in retrograde motion, or appearing to move westward across the night sky.

"Thus, for the three months around closest approach, the yellowish-orange planet will appear to move slowly backward from the constellation Gemini into Taurus," said Edward Murphy, an astronomer at the University of Virginia.

The exact distance between the two worlds varies during a close encounter, because the planets' orbits are elliptical.

Murphy calculates that today Earth is roughly 55 million miles (88 million kilometers) apart from Mars, a figure backed by Matthews.

But experts say this week's glimpse of the red planet is nothing compared to the show-stopping passage of August 27, 2003, when a mere 35 million miles (56 million kilometers) stood between the two bodies.

"That was when the red planet came closer than it had ever been since the time Neanderthals walked the Earth," Matthews said.

Best Views

Though Mars won't be as close to Earth as it was in 2003, this week's viewing might be better for some sky-watchers.

That's because Mars won't be as close to the Earth's horizon as it was four years ago, thanks to the astronomical geometry of this year's planetary opposition.

Continued on Next Page >>


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