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How long is a Martian year in Earth days?

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Mars An especially serene view of Mars (Tharsis side), a composite of images taken by the Mars Global Surveyor spacecraft in April 1999. The northern polar cap and encircling dark dune field of Vastitas Borealis are visible at the top of the globe. White water-ice clouds surround the most prominent volcanic peaks, including Olympus Mons near the western limb, Alba Patera to its northeast, and the line of Tharsis volcanoes to the southeast. East of the Tharsis rise can be seen the enormous near-equatorial gash that marks the canyon system Valles Marineris.

A Martian year, which represents the planet's sidereal period of revolution around the Sun, is approximately 686.98 Earth days long. This duration is often rounded to 687 Earth days in general contexts. Because of this orbital period, a year on Mars is nearly twice as long as a year on Earth.12