Orbit and Rotation
Mars's average distance from the Sun is roughly 230 million km (1.5 AU) and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours.
The axial tilt of Mars is 25.19 degrees, which is similar to the axial tilt of the Earth. As a result, Mars has seasons like the Earth, though on Mars, they are nearly twice as long given its longer year. Currently, the orientation of the north pole of Mars is close to the star Deneb. Mars passed an aphelion in March 2010 and its perihelion in March 2011. The next aphelion came in February 2012 and the next perihelion comes in January 2013.
Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury shows greater eccentricity. It is known that in the past, Mars has had a much more circular orbit than it does currently. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. The Mars cycle of eccentricity is 96,000 Earth years compared to the Earth's cycle of 100,000 years. Mars also has a much longer cycle of eccentricity with a period of 2.2 million Earth years, and this overshadows the 96,000-year cycle in the eccentricity graphs. For the last 35,000 years, the orbit of Mars has been getting slightly more eccentric because of the gravitational effects of the other planets. The closest distance between the Earth and Mars will continue to mildly decrease for the next 25,000 years.
Images comparing Mars's orbit with Ceres, a dwarf planet in the asteroid belt. The left is shown from the north ecliptic pole. The right is shown from the ascending node. The segments of orbits south of the ecliptic are plotted in darker colors. The perihelia (q) and aphelia (Q) are labelled with the date of nearest passage. The orbit of Mars is red, Ceres is yellow.Read more about this topic: Mars
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