If you wanted to travel to Mars, how long would it take? The answer depends on several factors, ranging from the position of the planets to the technology that would propel you there.
According to NASA, a one-way trip to Mars would take about nine months. If you wanted to make it a round-trip, all in all, it would take about 21 months as you will need to wait about three months on Mars to make sure Earth and Mars are in a suitable location to make the trip back home.
We take a look at how long a trip to the Red Planet would take using available technology and explore some of the factors that would affect your travel time.
How far away is Mars?
To determine how long it will take to reach Mars, we must first know the distance between the two planets.
In theory, the closest that Earth and Mars would approach each other would be when Mars is at its closest point to the sun (perihelion) and Earth is at its farthest (aphelion). This would put the planets only 33.9 million miles (54.6 million kilometers) apart. However, this has never happened in recorded history. The closest recorded approach of the two planets occurred in 2003 when they were only 34.8 million miles (56 million km) apart.
The two planets are farthest apart when they are both at their farthest from the sun, on opposite sides of the star. At this point, they can be 250 million miles (401 million km) apart.
The average distance between Earth and Mars is 140 million miles (225 million km).
Related: What is the temperature on Mars?
How long would it take to travel to Mars at the speed of light?
Light travels at approximately 186,282 miles per second (299,792 km per second). Therefore, a light shining from the surface of Mars would take the following amount of time to reach Earth (or vice versa):
- Closest possible approach: 182 seconds, or 3.03 minutes
- Closest recorded approach: 187 seconds, or 3.11 minutes
- Farthest approach: 1,342 seconds, or 22.4 minutes
- On average: 751 seconds, or just over 12.5 minutes
Fastest spacecraft so far
The fastest spacecraft is NASA's Parker Solar Probe, as it keeps breaking its own speed records as it moves closer to the sun. On Nov 21, 2021 the Parker Solar Probe reached a top speed of 101 miles (163 kilometers) per second during its 10th close flyby of our star, which translates to an eye-watering 364,621 mph (586,000 kph). According to a NASA statement, when the Parker Solar Probe comes within 4 million miles (6.2 million kilometers) of the solar surface in December 2024, the spacecraft's speed will top 430,000 miles per hour!
If the Parker Solar Probe managed to achieve the speeds reached during its 10th close flyby of the Sun and took a detour from its sun-focused mission to travel in a straight line from Earth to the Red Planet, the time it would take to get to Mars would be:
- Closest possible approach: 93 hours
- Closest recorded approach: 95 hours
- Farthest approach: 686 hours (28.5 days)
- On average: 384 hours (16 days)
The problems with calculating travel times to Mars
Of course, the problem with the previous calculations is that they measure the distance between the two planets as a straight line. Traveling through the farthest passing of Earth and Mars would involve a trip directly through the sun, while spacecraft must of necessity move in orbit around the solar system's star.
Although this isn't a problem for the closest approach, when the planets are on the same side of the sun, another problem exists. The numbers also assume that the two planets remain at a constant distance; that is, when a probe is launched from Earth while the two planets are at the closest approach, Mars would remain the same distance away over the 39 days it took the probe to travel.
Related: A brief history of Mars missions
In reality, however, the planets are continuously moving in their orbits around the sun. Engineers must calculate the ideal orbits for sending a spacecraft from Earth to Mars. Their numbers factor in not only distance but also fuel efficiency. Like throwing a dart at a moving target, they must calculate where the planet will be when the spacecraft arrives, not where it is when it leaves Earth. Spaceships must also decelerate to enter orbit around a new planet to avoid overshooting it.
How long it takes to reach Mars depends on where in their orbits the two planets lie when a mission is launched. It also depends on the technological developments of propulsion systems.
According to NASA Goddard Space Flight Center's website, the ideal lineup for a launch to Mars would get you to the planet in roughly nine months. The website quotes physics professor Craig C. Patten, of the University of California, San Diego:
"It takes the Earth one year to orbit the sun and it takes Mars about 1.9 years (say 2 years for easy calculation) to orbit the sun. The elliptical orbit which carries you from Earth to Mars is longer than Earth's orbit but shorter than Mars' orbit. Accordingly, we can estimate the time it would take to complete this orbit by averaging the lengths of Earth's orbit and Mars' orbit. Therefore, it would take about one and a half years to complete the elliptical orbit.
"In the nine months it takes to get to Mars, Mars moves a considerable distance around in its orbit, about three-eighths of the way around the sun. You have to plan to make sure that by the time you reach the distance of Mar's orbit, Mars is where you need it to be! Practically, this means that you can only begin your trip when Earth and Mars are properly lined up. This only happens every 26 months. That is, there is only one launch window every 26 months."
The trip could be shortened by burning more fuel — a process not ideal with today's technology, Patten said.
Evolving technology can help to shorten the flight. NASA's Space Launch System (SLS) will be the new workhorse for carrying upcoming missions, and potentially humans, to the red planet. SLS is currently being constructed and tested, with NASA now targeting a launch in March or April 2022 for its Artemis 1 flight, the first flight of its SLS rocket.
Robotic spacecraft could one day make the trip in only three days. Photon propulsion would rely on a powerful laser to accelerate spacecraft to velocities approaching the speed of light. Philip Lubin, a physics professor at the University of California, Santa Barbara, and his team are working on the Directed Energy Propulsion for Interstellar Exploration (DEEP-IN). The method could propel a 220-lb. (100 kilograms) robotic spacecraft to Mars in only three days, he said.
"There are recent advances which take this from science fiction to science reality," Lubin said at the 2015 NASA Innovative Advanced Concepts (NIAC) fall symposium. "There's no known reason why we cannot do this."
How long did past missions take to reach Mars?
Here is an infographic detailing how long it took several historical missions to reach the Red Planet (either orbiting or landing on the surface). Their launch dates are included for perspective.
Explore NASA's lunar exploration plans with their Moon to Mars overview. You can read about how to get people from Earth to Mars and safely back again with this informative article on The Conversation. Curious about the human health risks of a mission to the Red Planet? You may find this research paper of particular interest.