By Jeffrey Kluger
September 15, 2016

There were two things on Mars that seemed to be working hard to kill me: the lava tube and the omelette. I couldn’t decide which was worse.

I encountered the lava tube at the end of a 10-minute walk from my simulated Martian habitat, when I crested a ridge and turned my helmeted head down. Below was a basin about four stories deep and at least as wide across. At the center of it was a smaller, darker hole carved by molten lava that had long since flowed away. One wrong step in my clunky space boot and I could tumble straight down the geological drain.

Prudently, I backed away and returned to the station, and it was there that the omelette happened. I had volunteered to make a late lunch for myself and my two crewmates, and the ingredients on hand included bright yellow powdered eggs with dehydrated cheddar and Parmesan cheese. I mixed those things with enough water to make the dish vaguely egglike and cooked it with a little oil in a pan on a hot plate. That, eventually, yielded the “omelette.” It was “delicious.”

It was my great fortune that my time on Mars wasn’t spent on the real Mars but 8,200 ft. (2,500 m) up on the ruddy red flank of the Mauna Loa volcano in Hawaii. It was also my good fortune that my visit lasted only 24 hours. Other folks weren’t so lucky.

Just a few days earlier, a team of six scientists, engineers and aspiring astronauts had completed a full year in the simulated Mars habitat, known as HI-SEAS (Hawaii Space Exploration Analog and Simulation). The facility–which features a 1,200 sq. ft. (110 sq m) dome, equipped with a 424 sq. ft. (40 sq m) sleeping loft, two small bathrooms, a compact kitchen and a larder stocked with shelf-stable foods–is co-managed by NASA and the University of Hawaii.

Technically speaking, the crew could go outside for Mars walks (officially called extravehicular activity, or EVA) but they could do so only in full-body spacesuits. They could communicate with Mission Control and family members, but only via email or text–and they had to do so with a 20-minute one-way delay to simulate the light-time lag that exists between Mars and Earth. The reason for such strict protocols: for scientists to better understand how long-term, no-break space travel affects the human mind.

“If you’re claustrophobic, if you don’t like people, if you can’t adapt to a new environment, if you’re a picky eater, you shouldn’t do this,” said Christiane Heinicke, the crew physicist, shortly after the team emerged into a chilly Mauna Loa mist on the morning of Aug. 28.

Three HI-SEAS crews have gone before Heinicke’s, but no other mission lasted as long. Two former missions went for four months and one went eight. With this longer mission, researchers hope to come closer to understanding what makes a person mentally fit for the minimum two years of travel that would be required to send people to and from Mars.

Scientists already know how to build a spacecraft capable of making it to Mars, and thanks to more than 50 years of launching unmanned Mars probes, they know how to fly the route. Researchers are also learning more about how the body adapts to long-duration spaceflight, thanks in part to the year astronaut Scott Kelly and cosmonaut Mikhail Kornienko recently spent aboard the International Space Station. Still, the effects of long-term space travel on the mind remains something of a mystery.

For as long as scientists have been studying human behavior, they have looked at how we respond to ICE–isolated, confined and extreme–environments. Mars certainly qualifies: from the Red Planet, Earth would be reduced to just one more starry point in the sky, and the journey home would take a minimum of eight months.

“NASA needs to understand what happens with numerous teams for really long periods,” says Steve Kozlowski, an organizational psychologist at Michigan State University and a HI-SEAS researcher. “Only then can we know what to expect from a real Mars crew.”

Twelve different research teams have been conducting studies on this HI-SEAS mission, trying to understand stress management, workload, depression, group dynamics and more. They’re also investigating crew cohesion–and in my brief stay, I got a quick taste of why that’s so important.

I spent my Martian day with Arthur Cunningham, a member of the HI-SEAS support team from the University of Hawaii, and photographer Cassandra Klos. Did I love having Arthur’s well-curated Pandora channel on in the background as we went about our indoor work? I did. Did I appreciate the fact that after my omelette fiasco, Cassie offered to handle dinner and, through some hocus pocus, conjured up a pasta sauce that nearly made me swoon? I definitely did. But suppose things had gone differently?

Being mindful of your fellow interplanetary travelers is essential. For instance, Cyprien Verseux, the HI-SEAS team’s astrobiologist, learned to play the ukulele when the crew was in lockdown, but would practice it in a cold and uncomfortable lab trailer connected to the main habitat, so as not to disturb the rest of the crew. (In the main dome, there is no soundproofing.) But imagine having to live with death metal being played so loudly you can hear it even through somebody else’s earbuds. Imagine someone who gripes about a team member’s cooking but doesn’t offer to take over for the next meal.

Friction among crew members has occurred on all of the HI-SEAS missions, and sometimes the solution has been the opposite of the talk-it-out strategy used in many workplaces. “Usually, you can be open with someone and walk away and blow off steam, but you can’t do that in the hab, where you still have to sit and stare at the other person,” says University of South Florida organizational psychologist Wendy Bedwell, another HI-SEAS researcher. “What worked for one team was for some crew members simply to avoid each other for a while. They’d say, ‘O.K., Jack can’t work with Jane today.'”

Outdoor time was important too. “I went 21 days without an EVA once,” says environmental scientist and mission commander Carmel Johnson. “And then I went crazy.” She stresses that she means that figuratively, but that’s not a qualifier most people would be able to add.

My two EVAs were partly (O.K., mostly) about playing spaceman. Still, before I ventured out I learned two important bits of code: “Pan-pan,” which means non-life-threatening danger, and “Mayday,” which means what you think. Had I slipped, my moment at the ravine could have been a Mayday, and to my surprise, the exhausting trek up the hill in the Hawaii heat and the heavy spacesuit felt like it could have been a Mayday too.

Even if my excursions were mostly for fun, the HI-SEAS teams’ are not. They are sent out on simulated geology expeditions–that’s what they’d be doing on the real Mars, after all–because the combination of having a scientific purpose and being able to walk in a straight line without hitting the habitat wall can be vital to emotional well-being.

In the event of problems, HI-SEAS crew physician Sheyna Gifford had a small infirmary on-site that allowed her to handle routine illnesses and injuries. But for a serious problem, a crew member would have to be evacuated. On Mars, that isn’t an option. “There are 500 things you’d have to know how to treat, from headaches to hemorrhoids,” she says. “But cardiovascular collapse is not on the list–because you’re done.”

Then there are the more primal matters required by simulated space travel, like the flushless, composting toilets (which you can’t avoid even during a one-day stay) and the chilly, two-minute showers (which I could–and did–spare myself). For the one-year HI-SEAS mission, there were no showers at all for two weeks after a water pump broke; mission engineer Andrzej Stewart and architect Tristan Bassingthwaighte had to work to get it running again.

None of those minor hardships compare with what would be the epochal achievement of getting people on Mars–just as my 24 hours on faux Mars were nothing next to the year the HI-SEAS crew completed or the two-plus years a real Mars journey would take. But exploration has always been about incrementalism, learning how to do small, deliberate things before attempting a big and transformative thing. The work being done in a hab in Hawaii brings that very big achievement an important step closer.

Write to Jeffrey Kluger at jeffrey.kluger@time.com.

This appears in the September 26, 2016 issue of TIME.

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