Mars has an approximate orbital eccentricity of 0.093.
Orbital eccentricity describes how much an orbit differs from a perfect circle. An eccentricity of zero represents a circle, while larger values indicate a more elongated ellipse. Mars’s value of about 0.093 is considerably higher than Earth’s value of about 0.017, so Mars’s distance from the Sun changes more noticeably over the course of its year.
Mars reaches perihelion, its closest point to the Sun, at roughly 1.38 astronomical units, and aphelion, its farthest point, at roughly 1.67 astronomical units. This difference contributes to stronger seasonal contrasts between the two hemispheres, although Mars’s axial tilt also plays a major role.
Eccentricity is sometimes confused with axial tilt. Axial tilt measures the angle of a planet’s rotation axis, while eccentricity measures the shape of its orbit. Mars’s eccentric orbit is also one reason its seasons differ in length.