<P> The length of time for Mars to complete one orbit around the Sun is its sidereal year , and is about 686.98 Earth solar days , or 668.5991 sols . Because of the eccentricity of Mars ' orbit , the seasons are not of equal length . Assuming that seasons run from equinox to solstice or vice versa , the season L 0 to L 90 ( northern - hemisphere spring / southern - hemisphere autumn ) is the longest season lasting 194 Martian sols , and L 180 to L 270 ( northern hemisphere autumn / southern - hemisphere spring ) is the shortest season , lasting only 142 Martian sols . One commonly used system in the scientific literature denotes year number relative to Mars Year 1 ( MY1 ) beginning with the northern Spring equinox of April 11 , 1955 . </P>
<P> The length of time for Mars to complete one orbit around the Sun is its sidereal year , and is about 686.98 Earth solar days , or 668.5991 sols . Because of the eccentricity of Mars ' orbit , the seasons are not of equal length . Assuming that seasons run from equinox to solstice or vice versa , the season L 0 to L 90 ( northern - hemisphere spring / southern - hemisphere autumn ) is the longest season lasting 194 Martian sols , and L 180 to L 270 ( northern hemisphere autumn / southern - hemisphere spring ) is the shortest season , lasting only 142 Martian sols . One commonly used system in the scientific literature denotes year number relative to Mars Year 1 ( MY1 ) beginning with the northern Spring equinox of April 11 , 1955 . </P>
what is the length of year on mars
what is the length of year on mars
about 686.98 Earth solar days
about 686.98 Earth solar days