The Tricky Logistics of Putting People on Mars

For as long as humans have looked to the stars, we’ve dreamed of venturing out and visiting these distant places. And no place has been the target of more speculation than Mars. Now, we’re finally at a place where the dream of human beings setting foot on another planet could become a reality within our lifetimes.

We understand the technology we need to send humans to Mars, and we have the experience of sending robotic missions there as well. So when are we going to take that next giant leap and send a crewed mission to another planet for the first time? And what will it take to make that happen?

We spoke to space expert Michael Hecht of the Massachusetts Institute of Technology, veteran of the Jet Propulsion Laboratory and principal investigator of the MOXIE oxygen-making instrument on the Perseverance rover, to understand how we get from Earth to Mars — and how we’ll get boots on the ground for the first time.

humans on mars nasa concept

Always 15 years away

With the recent flurry of interest in Mars exploration, it feels like we’re closer than ever before to actually getting people on the surface of the planet. And yet, it’s also a goal that constantly seems to be just out of reach.

We have the technology to make a crewed Mars mission happen now, and there is increasing interest in the topic.

After the Apollo missions of the 1960s and 1970s, many space enthusiasts assumed we would keep reaching and exploring, and move on to the next target for exploration: Mars. But public interest waned, support for Apollo dried up, and humans haven’t left Earth orbit since.

In the intervening decades, many have speculated that humans would set foot on Mars in only 15 years; that inevitably we’ll end up on the red planet soon. But a concrete, serious mission plan to put people on Mars has yet to materialize.

We have the technology to make a crewed Mars mission happen now, and there is increasing interest in the topic. But Hecht argues that the space community, and we as a species as a whole, have yet to make a serious financial and practical commitment to really make a mission happen. If we decided to do this, we could. But we need to make that commitment.

“We could have gone after Apollo,” Hecht said. “It would have been hard, and it would have been dangerous. But we can do it more safely now. We could have gone then, and we can go now.”

One magic spot in the cycle

When trying to picture what a crewed Mars mission might look like, there’s really only one practical way to get from here to there. Due to Mars’s orbit around the sun, a year there lasts just under two Earth years. Allowing for travel time, that means if you want to travel from Earth to Mars, there’s one period in a 26-month cycle when that journey is easiest: When the two planets are close and a rocket can be sent into what is called a Hohmann transfer orbit.

mars earth oppositions

“There’s one magic spot in that 26-month cycle,” Hecht explained. When a rocket launches from Earth at just the right time, it can intersect Mars’s orbit at the same time Mars does. “It’s like changing lanes on the highway.”

Although it is possible to send craft to Mars using other orbits, it’s more difficult and dangerous, and a lot more expensive. So this 26-month cycle puts a practical limit on when we can send missions to Mars. It’s why Mars missions often launch around the same time, like the three spacecraft which launched in summer 2020 — NASA’s Perseverance rover, China’s Tianwen-1 mission, and UAE’s Hope mission.

And there’s an equivalent opportunity to come back in the other direction. This puts a pragmatic frame around what a crewed Mars mission will look like: A six- or seven-month journey from Earth to Mars, a bit over a year and a half on the surface, and another six or seven months coming back. That’s around a three-year mission in total.

A longer mission than we’re used to

3D Sculptor/Shutterstock

That three-year mission length poses…

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