Mars

When Mars is closest to Earth

Every 26 months Earth catches up with Mars. How close the two come varies by almost a factor of two — and the moment to leave for Mars is not the moment it is nearest.

Why the distance varies so much

Earth completes an orbit in 365 days and Mars in 687, so Earth laps it every 780 days or so. Each lap produces a close approach. But Mars has the second most elliptical orbit of any planet — its distance from the Sun swings between 207 and 249 million kilometres — so it matters enormously where in that orbit the two planets happen to meet.

Meet Mars near its perihelion and the gap closes to about 56 million kilometres. Meet it near aphelion and the same alignment leaves 101 million kilometres between you, almost twice as far. That is the difference between a disc 25″ across in a telescope and one barely 14″ across — and the difference between a fast, cheap crossing and a slow, expensive one.

The approach of 20 February 2027 is a poor one: at 101.4 million km it is the most distant in the whole of the next century. The next genuinely good one is 11 September 2035, at 56.9 million km — in 9 years.

Close approaches to 2054

The date of closest approach, not the date of opposition — they differ by up to a week and a half, because opposition is a matter of longitude and closeness is a matter of distance.

Marked great when the gap falls under 60 million km, which is the usual threshold for calling an opposition a great one.

Getting there: the launch windows

This is the part that catches people out. You cannot leave for Mars when Mars is closest, because by the time you arrive it will have moved on. The crossing takes 200 to 260 days, during which Mars travels more than a third of the way around its orbit — so you leave while Mars is still well ahead of Earth and let it come to you. That is the geometry drawn at the top of this page.

"Well ahead" has a number. Every Mars mission that has flown departed with Mars between 25° and 58° ahead of Earth around the Sun, and the windows below are the dates that span. An individual mission takes a narrower slot inside it, chosen for its rocket and its mass.

Checked against missions that actually flew

The geometry above is only worth anything if it describes real departures. These are the four most recent successful Mars launches, with the angle recomputed from their real launch dates rather than stored — so if the calculation here ever drifts, these stop lining up.

All four fall inside the 25°–58° span, and all four crossed faster than the 259-day minimum-energy transfer: every real mission spends fuel to arrive sooner than the textbook says it must.

The 2003 record, and whether it will be beaten

On 27 August 2003 Mars came within 0.37271 AU — 55.76 million kilometres — the closest in roughly 60,000 years. It was a genuinely exceptional alignment: a near-perfect coincidence of opposition with Mars's own perihelion.

It is not beaten in the next century. Of the 45 close approaches between now and 2121, the nearest is 30 August 2082 at 0.37354 AU — 124 thousand kilometres short of the record.

Worth knowing before you plan an evening around it: even at its record closest, Mars is about 25 arcseconds across — the Moon is some 72 times wider. To the naked eye Mars is a bright orange star and nothing more, at every distance. The difference a close approach makes is real, but it is a telescope difference rather than a step-outside-and-gasp one.

Common questions

When is Mars closest to Earth?

The next close approach is 20 February 2027, when Mars will be 101.4 million kilometres away — 0.678 AU. The closest approach in the next twenty years is 11 September 2035 at 56.9 million km.

How often does Mars come close to Earth?

Every 26 months, give or take a few weeks. Earth laps Mars once per synodic period of about 780 days, and each lap brings the two planets to their nearest point. How near varies enormously — between 55 and 101 million kilometres — because Mars has a markedly elliptical orbit.

When is the next launch window to Mars?

The next departure window runs from 8 November 2026 to 7 January 2027 — 59 days, in 30 days. A spacecraft leaving in it arrives between June 2027 and August 2027.

Why do missions launch months before Mars is closest?

Because the crossing takes seven to nine months. You aim at where Mars will be on arrival, not where it is at departure, so you leave while Mars is still well ahead of Earth in its orbit — around 25 to 58 degrees ahead. By the time the spacecraft arrives, Mars has moved into position to meet it.

Was 2003 really the closest Mars has been in 60,000 years?

Yes: 27 August 2003, at 0.37271 AU or 55.76 million kilometres. It is not beaten in the next century — the closest approach between now and 2121 is 30 August 2082 at 0.37354 AU, which falls just short.

Distances computed from VSOP87 via Astronomy Engine, with each closest approach found by minimising the Earth–Mars distance directly rather than assuming it falls at opposition. Reproduces the published 2003, 2018 and 2020 figures to five decimal places in AU. See Mars right now, watch the two orbits close in the live simulation, or check whether Mars is up tonight from where you are.