Earth and Mars are constantly rotating, but do not keep a constant distance from each other. Also, spacecraft do not travel in a straight line to their destination.
To reach Mars in the fastest and most efficient way, NASA’s Orion spacecraft will follow the Hohmann transfer orbit – the path that requires the least amount of energy. Credit: NASA.
I’ve read that planned manned Mars missions will take six months or two years to arrive. which is it? Can a heavy payload cause a longer trip? It took only eight to nine months for our rovers to arrive.
ronald green
Kingman, Arizona
When it comes to traveling to the Red Planet, your mileage may vary – literally. Earth and Mars are constantly rotating, but they do not remain at a constant distance from each other. Furthermore, spacecraft from Earth do not travel in a straight line to the Red Planet. Instead, astronauts leaving Earth will follow a path known as the Hohmann transfer orbit, an ellipse from where Earth is now to where Mars will be in the future. This orbit requires the least energy (and thus the least fuel) and allows the spacecraft to reach it within seven to nine months.
But you can’t just decide to take the bus and go. Mars and Earth are only in their best positions for interplanetary travel every 26 months. A launch outside that window could dramatically extend the time the spacecraft – and any astronaut – spends in space.
NASA’s Orion spacecraft will carry crew members to Mars atop a Space Launch System (SLS) rocket, more powerful than the Saturn V rocket that has taken astronauts to the Moon. The agency first tested the pair in 2022 with Artemis 1 (formerly called Exploration Mission-1 or EM-1), an unmanned mission to orbit around the Moon and return to Earth. The agency now plans to launch Artemis 2, which will send a crewed Orion capsule around the moon, in March 2026.
Nola Taylor Tillman
independent science journalist and Astronomy Contributor
This Question and Answer was originally published in the June 2018 issue. This has been updated to include information about the Artemis 1 and 2 missions.
