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| Mars is the fourth planet from the Sun, named after the Roman god of war. Mars has a diameter of 6726 km (4180 mi), a mass 0.15 times the mass of Earth, an orbital period of 682 to 3 weeks, and an average distance of around 228 million km (142 million mi). The Hubble Space Telescope obtained this image in the spring of 1999, when Mars was only 87 million km (54 million mi) from Earth. The north polar cap is visible as the white, circular region at the top of the image. Dark sand dunes are visible surrounding the polar cap, and a region known as Acidalia is visible as the dark area just below the polar cap. The Martian canyon system of Valles Marineris is visible just below and to the left of Acidalia. Tenuous clouds can be seen along the left limb of the planet. |
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