How Long Does It Take to Get to Mars? Launch Windows Explained Simply

By Austin Little

The short answer is roughly six to nine months. The real answer involves moving targets, a two-year calendar, and why rockets don't just point at Mars and go.

AI disclosure. This page was drafted with AI assistance and edited for Apiary. Facts that need a live check are marked. We don't invent quotes, stats, people, or events. If something looks off, tell Austin — that's the point of a living hive.

Ask most people how long it takes to get to Mars and you'll hear a range of guesses: a few weeks, a year, "it depends." The people who say "it depends" are right, but that's not very satisfying.

Here's the satisfying version. A typical spacecraft trip from Earth to Mars takes somewhere around six to nine months.  But the "why" behind that number is one of the coolest pieces of everyday physics you can learn. It explains why Mars missions launch in bunches, why they can't leave whenever they want, why astronauts couldn't just turn around and come home, and why "the shortest path" is almost never the path rockets take.

This guide is written for someone who's curious, not someone who's taking an exam. No equations required. By the end, you'll be able to explain launch windows to your kids, your coworkers, or the person next to you at the planetarium.

The short answer

Typical trip: about six to nine months for robotic missions using the standard, fuel-efficient route.
Why not faster? Going faster takes a lot more fuel, and you also have to slow down when you get there.
Why not whenever? Earth and Mars are both moving around the Sun at different speeds. The good lineups for a trip happen only about every 26 months. Those are called launch windows.
Round trip for humans? Because of how the planets line up, a full round trip using the efficient route could mean months of travel each way plus a long wait on Mars for the return window — often described as roughly two and a half to three years total for some mission designs.

Now let's unpack why.

Why you can't just point at Mars and fire

Imagine you're standing on a merry-go-round, and a friend is standing on a bigger, slower merry-go-round nearby. You want to toss them a ball. If you throw straight at where they are right now, by the time the ball arrives, they've moved. And you're moving too, which affects the ball's path the moment it leaves your hand.

That's the whole puzzle in one picture.

Everything is already moving

Earth orbits the Sun at an enormous speed. So does Mars, a bit more slowly, on a bigger loop farther out. A spacecraft sitting on a launch pad is already moving with Earth around the Sun. When it launches, it doesn't start from zero; it starts with all of Earth's orbital speed and adds a little more.

The Sun is the boss

Once a spacecraft leaves Earth's neighborhood, the Sun's gravity dominates its path. The spacecraft doesn't travel in a straight line. It travels in an orbit around the Sun, just like a planet. Its path is a curve — part of an oval-shaped orbit called an ellipse.

So the question isn't really "how do I fly to Mars?" It's "how do I change my orbit around the Sun so that it crosses Mars's orbit at the exact moment Mars is there?"

Fuel is the price of every change

In space, you change your path by firing engines, and every change costs fuel. Fuel is heavy. Carrying more fuel means you need a bigger rocket to lift that fuel, which needs more fuel, and so on. This snowballing problem is why mission planners are obsessive about efficient routes. Every bit of fuel saved can become more science instruments, more supplies, or a smaller, cheaper rocket.

The efficient route: the Hohmann transfer

In the 1920s, a German engineer named Walter Hohmann worked out a very fuel-efficient way to move between two circular orbits.  His idea is now called the Hohmann transfer orbit, and it's the basic starting point for understanding most Mars trips.

Here's how it works, in plain English:

Start in Earth's orbit around the Sun. (Which you're already in, because you're on Earth.)
Fire your engine to speed up in the same direction Earth is moving. This stretches your orbit into an oval. The near end of the oval stays at Earth's distance from the Sun. The far end now reaches out to Mars's distance.
Coast along the oval for about half a lap. No engine needed. The Sun's gravity does the steering.
Arrive at the far end of the oval, right where Mars's orbit is — and if you timed it right, Mars is there too.
Fire again (or use the atmosphere to slow down) to match Mars's speed and get captured into orbit or descend to land.

The key insight: you're riding halfway around the Sun on a curved path. That's why the trip takes months. You aren't driving a straight road across the gap between the planets. You're swinging around in a big arc.

Real missions don't use a perfect textbook Hohmann transfer. Planetary orbits aren't perfect circles and aren't perfectly flat with each other, so engineers tweak the route, picking trajectories that are a bit faster or a bit cheaper depending on the year and the mission's needs. But the Hohmann picture is the backbone of the idea.

Where the "about eight and a half months" number comes from

You can get surprisingly close to the real trip time with one old rule and some grade-school arithmetic. No calculator tricks, just the idea.

In the early 1600s, Johannes Kepler noticed a pattern in how planets move: the bigger an orbit is, the longer it takes to go around, in a very specific way. If you measure distances in "Earth-to-Sun units" (astronomers call one of these an astronomical unit, or AU) and time in Earth years, then the time for one lap, multiplied by itself, equals the size of the orbit multiplied by itself three times. Earth sits at 1 AU and takes 1 year. Mars sits at about 1.52 AU and takes about 1.88 years, or roughly 687 days.

Now apply the same rule to the transfer oval. Its near end touches Earth's orbit (1 AU) and its far end touches Mars's orbit (about 1.52 AU), so its "average size" is halfway between: about 1.26 AU. Plug that into Kepler's rule and a full lap around that oval would take about 1.42 years. But the spacecraft only rides half the oval, from the near end to the far end. Half of 1.42 years is about 0.71 years, which is roughly 259 days, or about eight and a half months.

That's the textbook answer for the most fuel-efficient path between two idealized circular orbits. Real missions land on either side of it. Some years the geometry lets planners shave weeks off; some missions deliberately pick a slightly faster, slightly more expensive path because arriving in a particular Martian season matters for landing or for solar power. That's how you end up with a real-world range of roughly six to nine months instead of one fixed number.

So what is a "launch window"?

Because the transfer takes you halfway around the Sun, you have to launch when Mars is in the right spot ahead of Earth so that, months later, Mars arrives at the meeting point at the same time you do. Launch too early or too late, and you show up at Mars's orbit while Mars is somewhere else.

Earth goes around the Sun faster than Mars does. So Earth keeps "lapping" Mars, like a faster runner on an inner track. The right geometry for a Mars trip comes around once every time Earth laps Mars, which works out to about every 26 months — a bit over two years.

Why Mars has to be "ahead" when you leave

Here's the same idea with numbers. If the trip takes about 259 days, how far does Mars move while you're coasting? Mars needs about 687 days for a full 360-degree lap, so in 259 days it covers a bit over a third of a lap: roughly 136 degrees.

Your spacecraft, meanwhile, travels exactly halfway around the Sun, 180 degrees, from launch point to arrival point. For Mars to be waiting at the arrival point, it has to start the race about 180 minus 136, or roughly 44 degrees ahead of Earth. Picture a clock face with the Sun in the middle: if Earth is at 12 o'clock, Mars needs to be sitting at about half past one.

Earth only catches Mars in that exact relative position once per "lap," which is where the 26-month rhythm comes from. If you're curious, the math is the same kind of thing as two clock hands: Earth gains about 0.46 degrees on Mars every day, so it takes about 780 days to gain a full circle and recreate the same lineup.

A launch window is the stretch of time around that ideal lineup when a launch is practical with the rocket and fuel you have. It's typically a few weeks long. Outside the window, reaching Mars would take a lot more fuel or a much longer trip, or simply isn't possible with that spacecraft.

That's why you'll see multiple Mars missions from different countries launching within weeks of each other. They aren't copying each other. They're all catching the same bus.

A real example

In 2020, three different Mars missions launched in the same summer window: NASA's Perseverance rover, the United Arab Emirates' Hope orbiter, and China's Tianwen-1.  NASA's Perseverance launched in late July 2020 and landed in Jezero Crater on February 18, 2021, after a trip of roughly seven months.  That's a textbook example of the six-to-nine-month range in action.

Travel times of some real missions

Perseverance wasn't a fluke. Look across decades of Mars missions and the same range keeps showing up. These are approximate, measured from launch to arrival at Mars:

Mariner 4 (NASA flyby): launched late November 1964, flew past Mars in mid-July 1965. About seven and a half months, and it sent back the first close-up pictures of another planet.
Viking 1 (NASA orbiter and lander): launched August 1975, reached Mars orbit in June 1976. About ten months, with the landing following the next month after the team scouted a safer site.
Mars Pathfinder (NASA lander with the Sojourner rover): launched December 1996, landed on July 4, 1997. About seven months.
Curiosity (NASA rover): launched late November 2011, landed in early August 2012. About eight and a half months.
InSight (NASA lander): launched May 2018, landed late November 2018. About six and a half months.

Notice that nobody in that list made it in three months, and nobody took two years. Six to ten months is simply what chemical rockets and planetary geometry give you.

What happens if you miss the window?

You wait. If a mission isn't ready in time — a technical problem, a delay in testing — it may have to sit on the ground for about two years until the next window. This has happened to real missions, and it's one of the most expensive kinds of delay in spaceflight because the team, the facilities, and the spacecraft all need to be maintained during the wait.

How far away is Mars, anyway?

This is where people get tripped up, because there's no single answer. The distance between Earth and Mars changes constantly as both planets move.

When they're closest — when Earth passes between Mars and the Sun on the same side — Mars can be somewhere around 55 to 60 million kilometers away (roughly 34 to 37 million miles), depending on the year.
When they're farthest — on opposite sides of the Sun — Mars can be around 400 million kilometers away (roughly 250 million miles).

That's a huge swing. And here's a twist that surprises people: spacecraft don't launch when Mars is closest. Because of the curved transfer path, the spacecraft is aimed at where Mars will be months later. Launch typically happens a bit before Earth and Mars make their closest approach, and the spacecraft travels a distance far longer than the straight-line gap — often hundreds of millions of kilometers along its curved path.

The light-speed delay

Even radio signals, which travel at the speed of light, take a while. Depending on where the planets are, a message from Earth to Mars takes somewhere between about 3 and 22 minutes one way.  That's why Mars rovers can't be driven with a joystick like a video game. Engineers send a batch of instructions, the rover carries them out, and the team waits to see what happened. It's also why landings are fully automatic: by the time Earth hears that a spacecraft has entered the atmosphere, it has already landed (or not).

Arriving is its own adventure

"Getting to Mars" doesn't end when the spacecraft reaches Mars. It's arriving several times faster than a rifle bullet, relative to the planet, and it has to shed that speed one way or another.

Orbiters: brake, then skim the air

A spacecraft that wants to stay in orbit fires its engine to slow down just enough for Mars's gravity to capture it. That first orbit is usually a long, stretched-out loop. Many orbiters then use a patient trick called aerobraking: they dip the low point of their orbit into the very top of the thin Martian atmosphere over and over, letting air drag shave off a little speed each pass. It saves a huge amount of fuel, but it can take months of careful passes before the orbiter reaches its final science orbit.

So when someone asks how long it took an orbiter to "get to Mars," the honest answer might be "seven months to arrive, plus several more to settle into the orbit it actually works from."

Landers: the famous few minutes

Landers don't get that luxury. They hit the atmosphere and have to go from interplanetary speed to a gentle touchdown in roughly seven minutes. NASA engineers have nicknamed this the "seven minutes of terror."  A heat shield takes the brunt of the friction first, then a supersonic parachute opens, then rockets or other systems handle the last stretch. Because of the radio delay described above, all of it happens automatically. By the time the first signal saying "we've hit the atmosphere" reaches Earth, the outcome has already been decided.

Mars makes this especially tricky. Its atmosphere is thick enough to heat a spacecraft dangerously but far too thin to slow it down with a parachute alone. Earth's air is roughly a hundred times denser at the surface.  That's why every successful Mars landing has stacked several braking methods together.

The two-week quiet period

There's one more timing quirk worth knowing. Roughly every two years, Mars passes behind the Sun from our point of view. This is called solar conjunction. The Sun's hot, electrically charged outer atmosphere can scramble radio signals that pass close to it, so mission teams usually stop sending commands for a couple of weeks and let spacecraft run on simple, preloaded plans.

It isn't dangerous, and it's planned years ahead. But it's a nice reminder that the same orbital dance that sets launch windows also sets the rhythm of day-to-day mission work.

Can we go faster?

Yes, but it costs a lot.

The fuel problem

To shorten the trip, you have to leave Earth faster, which takes more fuel. Then, because you're arriving faster, you have to slow down more at Mars, which takes even more fuel (or a much tougher heat shield, if you're using the atmosphere to brake). Remember the snowball: more fuel means a bigger rocket, which means more fuel. Shortening the trip by a couple of months can demand a dramatically bigger launch.

Future propulsion ideas

Engineers have studied several ways to cut travel time:

Bigger, more powerful rockets that can throw heavier spacecraft on faster paths.
Nuclear thermal propulsion, which heats propellant with a nuclear reactor and could be more efficient than chemical rockets. NASA has funded research and development in this area.
Electric propulsion (like ion engines), which is very fuel-efficient but produces gentle thrust over long periods. It's used today on some robotic missions to other destinations.
In-space refueling, which would let a ship launch light and fill up in orbit before heading out.

Some studies and proposals have described human trips to Mars in a few months with advanced propulsion, but these are not yet operating technologies.  For now, six to nine months is the realistic ballpark for the trips we actually fly.

Why the round trip is the hard part

Getting there is half the story. Getting back is where launch windows really bite.

When a crew arrives at Mars using an efficient route, Earth and Mars have moved. The lineup for an efficient trip home doesn't happen right away. In many mission designs, the crew would have to wait on or around Mars for over a year before the next good return window opens.

Mission planners talk about two broad styles:

Long-stay missions: Efficient trips both ways, with a long stay at Mars waiting for the return window. Lots of time for exploring; long total mission.
Short-stay missions: A shorter visit at Mars, but the return trip uses a less efficient path that may take longer or swing closer to the Sun, and requires more fuel.

Neither is free. Either way, astronauts would be committed to a mission measured in years. There's no "quick turn back" once you leave, which is a big reason human Mars missions are so demanding to plan.

What a long trip means for people

Robotic spacecraft don't mind a long trip. Humans do. A crew heading to Mars would deal with:

Space radiation. Beyond Earth's protective magnetic field, astronauts are exposed to more radiation from the Sun and from deep space. NASA treats radiation as one of the major human health risks for Mars missions.
Weightlessness. Long stretches without gravity weaken bones and muscles and affect eyesight and other body systems. Astronauts on the International Space Station exercise daily to fight this.
Isolation and distance. With a communication delay of many minutes, real-time conversations with home aren't possible. Crews would need to handle emergencies on their own.
Supplies. Food, water, air, and spare parts for years, with no resupply runs.

That's why shaving even a few months off the trip matters so much for human missions — and why it gets so much engineering attention.

A simple way to picture the whole thing

Here's a mental model you can carry around.

Picture two runners on a circular track. Earth is on the inside lane, running faster. Mars is on the outside lane, running slower.
You want to toss a package from the inside runner to the outside runner. The package can't go straight across. It has to curve outward in an arc, and it takes time to travel.
You throw it early, when the outside runner is a bit ahead, so the package and the runner meet at the same spot.
The right moment to throw comes around only when the inside runner catches up to the same position again — every 26 months or so in the real solar system.
To catch a ride home, the package has to wait until the runners line up the other way around.

That's launch windows in a nutshell.

Common myths and mix-ups

"Mars is closest every year." No. Close approaches happen about every two years, and some are much closer than others because Mars's orbit is more oval-shaped than Earth's.

"Rockets fly in straight lines." No. Once out of Earth's grip, spacecraft follow curved orbits around the Sun.

"We should launch when Mars is closest." Not quite. Because of the curved path, launches usually happen somewhat before closest approach so the spacecraft arrives where Mars will be.

"You can turn around halfway if something goes wrong." For most practical trajectories, no. Changing course dramatically would take fuel the spacecraft doesn't have. Some mission designs include "free-return" style paths for certain trips, but Mars missions generally can't simply U-turn.

"Faster is always better." Faster costs fuel, and fuel costs mass, money, and risk. For robots, slow and efficient is usually the smart call.

Frequently asked questions

How long did it take Perseverance to get to Mars?

Roughly seven months: it launched in late July 2020 and landed on February 18, 2021.

Why do Mars missions launch only every two years?

Because the lineup of Earth and Mars that makes an efficient trip possible comes around about every 26 months, as Earth laps Mars in their orbits around the Sun.

How far will a spacecraft travel to reach Mars?

Much farther than the straight-line distance between the planets, because it follows a curved path around the Sun. It's typically in the hundreds of millions of kilometers.

Could humans get to Mars faster than robots?

They'd want to, for health and supplies. Doing it requires more powerful or more efficient propulsion than missions use today, or bigger rockets carrying more fuel. Research is ongoing.

How long would a round trip to Mars take for astronauts?

It depends on the mission design. Using efficient routes, many concepts involve months of travel each way and a long wait on Mars for the return window, adding up to well over two years total.

Why can't Mars rovers be driven live?

Radio signals take several minutes to travel between Earth and Mars, and sometimes over 20 minutes one way. Rovers carry out pre-planned commands and use onboard smarts to avoid hazards.

Are some launch windows better than others?

Yes. Mars's orbit is noticeably more oval than Earth's, so some lineups happen when Mars is relatively close to the Sun and others when it's farther out. Favorable windows need less energy or allow somewhat shorter trips, and the pattern of especially good and especially poor windows repeats over roughly fifteen to seventeen years.  Mission planners know these cycles well in advance and often schedule the most demanding missions for the friendlier years.

Does it take the same time to come back?

Roughly, yes. The efficient path home is a mirror image of the path out: half an oval from Mars's orbit back down to Earth's. The catch isn't the length of the return flight. It's waiting for the planets to line up for it.

Could a spacecraft just keep cycling between Earth and Mars?

Engineers have studied this. The concept, often called a Mars cycler, is a large spacecraft on a looping orbit that swings past both planets again and again, with smaller vehicles ferrying crews on and off. It's an idea on paper, not something that has flown.

When is the next Mars launch window?

Launch windows recur about every 26 months. To find the next one, check NASA or another space agency's mission pages, which list upcoming launch periods.

The takeaway

Getting to Mars takes about six to nine months, not because space is slow, but because we're playing a game of catch between two moving planets using as little fuel as possible. Spacecraft ride a curved path halfway around the Sun, and they have to launch when the planets are lined up just right, which happens roughly every two years. Miss the window, and you wait for the next one.

Next time you hear that several countries are launching to Mars in the same month, you'll know why: the bus only comes every 26 months, and everybody wants to be on it.