How long is Mars's orbit?

Mars takes 687.0 days to go once round the Sun. It is travelling at 23.41 km/s at the moment — a speed that changes through the orbit, fastest at perihelion and slowest at aphelion.

What shape is Mars's orbit?

An ellipse with the Sun at one focus, not at the centre. Its eccentricity is 0.0935, derived here from the perihelion and aphelion distances rather than quoted: 1.381 AU at closest and 1.666 AU at furthest, a difference of 42,624,337 km.

Where is Mars in its orbit now?

1.570 AU from the Sun — 0.235 billion km — which is 66% of the way from its closest point to its furthest. It next reaches aphelion on 4 March 2027.

Mars

Mars's orbit

Once round the Sun every 687.0 days, on an ellipse drawn here from the ephemeris rather than from a formula.

Looking down on the plane of the ecliptic, traced from the ephemeris over one full orbit of 687 days. Earth’s orbit is the faint one, for scale. The Sun sits off the centre of the ellipse — that offset is the eccentricity, and it is why the two distances differ.

Orbital period: 687.0; days for one lap
Eccentricity: 0.0935; 0 would be a circle
Semi-major axis: 1.524; AU · the orbit's average radius
Speed now: 23.41; km/s, from the ephemeris

What is worth knowing about it

Mars has the second most eccentric orbit of the eight, which is why some oppositions bring it within 56 million km of Earth and others leave 101 million. Everything about when to launch there and when to look at it follows from this one number.

The shape of it

Mars does not travel a circle. It comes as close as 1.381 AU (0.207 billion km) and goes as far as 1.666 AU (0.249 billion km) — aphelion is 1.21 times further out than perihelion, a swing of 42,624,337 km. At 0.0935 the orbit is noticeably off-centre: Mars is measurably closer to the Sun at one end of it than the other.

Because the Sun sits at a focus rather than the centre, Mars does not move at a constant speed either. It runs fastest when it is closest and slowest when it is furthest, sweeping equal areas in equal times — which is Kepler's second law, and is visible in the diagram above as the uneven spacing of a constant time step.

Where it is now

Today Mars is 1.570 AU from the Sun, 66% of the way from perihelion to aphelion, travelling at 23.41 km/s. It reaches aphelion on 4 March 2027 at 1.666 AU.

Common questions

How long is Mars's orbit?: Mars takes 687.0 days to go once round the Sun. It is travelling at 23.41 km/s at the moment — a speed that changes through the orbit, fastest at perihelion and slowest at aphelion.
What shape is Mars's orbit?: An ellipse with the Sun at one focus, not at the centre. Its eccentricity is 0.0935, derived here from the perihelion and aphelion distances rather than quoted: 1.381 AU at closest and 1.666 AU at furthest, a difference of 42,624,337 km.
Where is Mars in its orbit now?: 1.570 AU from the Sun — 0.235 billion km — which is 66% of the way from its closest point to its furthest. It next reaches aphelion on 4 March 2027.

Positions from VSOP87 via Astronomy Engine, accurate to within one arcminute. The orbit above is traced by sampling a full period rather than drawn from elements, so the tilt and the off-centre Sun are the real ones. See Mars’s distance from the Sun, Mars right now, or watch the whole system move in the live simulation.