It's been a quarter of a century since eight scientists volunteered to shut themselves inside the world's largest science laboratory in the middle of the desert.
Little did they know the amount of publicity their mission would generate. The whole world watched as the four men and four women entered the 3.14-acre structure in the middle of the Sonora Desert in Arizona.
"It was an extraordinarily audacious idea," Jane Poynter, one of the human guinea pigs who took part in the experiment reminisces. "We were attempting to take this biosphere that evolved on a planetary scale and reduce it in size and complexity so we could understand more about our planet.
"And to do that was the most exciting thing I could possibly have gotten involved with at the time."
Poynter, who spent her 30th birthday inside B2, had been on the design team, working on the project for years before she was handpicked as one of the select few.
"The day we went in was a culmination of years of all our work," she says.
The training programme she describes as "unorthodox but quite effective". Poynter was sent off to the wild outback in Australia, and spent a year with Aboriginals.
"It was awesome, riding around on horseback, mending fences, doing cool ecological work. Parts of the year you were completely cut off because of floods. So you really get a sense of what it’s like to be cut off from the world."
Another project included being on a boat which sailed the Indian Ocean.
"It was a dream come true for me, but for some people it wasn’t. They were like ‘oh no, no, this isn’t for me’. So it was these two projects that were a large part of sorting the wheat from the chaff of people who could really thrive in that kind of setting."
Poynter eventually entered the sealed artificial world on September 26, 1991, along with medical doctor and researcher Roy Walford, Taber MacCallum - whom she later married - Mark Nelson, Sally Silverstone, Abigail Alling - who replaced Silke Schneider - Mark Van Thillo, and Linda Leigh.
The project hit headlines across the world.
"We were completely taken by surprise by the amount of publicity," Poynter recalls. "Totally unprepared for that amount of publicity. I just didn’t read it, I ignored it. I just went and grew my sweet potatoes.
"You have to put this in historic context. When we started building B2, we were spelling the word 'biosphere' to people. It wasn’t even a concept then. It wasn’t something people had thought about.
"When we went into the biosphere, we were really just hoping that it was possible to do."
Living in the Biosphere was "a bit like living in a ship," Poynter says.
"We got up in the morning and everyone had their roles. So I was in charge of the farm. Everyone would come and help for a couple of hours in the morning, grow our food, harvest our food. I would work in the lab for several hours in the afternoon."
The agricultural system in the lab produced 83% of the crew's total diet, which included crops of bananas, papayas, sweet potatoes, beets, peanuts, lablab and cowpea beans, rice, and wheat. No chemicals could be used.
"It was very varied. I mean, we had a whole planet to manage. We were recycling all our water, all our air, growing all our food. Nothing was going in or out, it was truly hermetically sealed.
"The building was sealed tighter than the ISS. That’s how tight it was. It was incredible."
During their time on the mission, the crew were subjected to severely low levels of oxygen, never-ending hunger and infighting. The team split into two warring factions, each with different ideas of what the project should be trying to achieve.
"I was very naive about how hard the human interaction part would be," Poynter, who is back at Biosphere 2 for the One Young World environmental summit, admits. "And possibly hadn’t really thought about it in the way that I should have. Certainly the human component was not as easy as I was hoping. We were a bunch of type As, so you can imagine.."
The project was dogged by controversy and bad press. The mission was accused of being "New Age drivel masquerading as science," while the participants were accused of being in a cult. In 1992, the hungry scientists started eating emergency food supplies that had not been grown inside the bubble. Levels of CO2 fluctuated "wildly" and many of the pollinating insects died. Oxygen levels fell, meaning some biospherians started to suffer from sleep apnea and fatigue, as the conditions were akin to being at 13,400ft. The medical team eventually decided to boost oxygen with injections.
There was added controversy when the public learnt one injured team member had been allowed to leave for treatment, and returned with external materials - although the crew maintains only plastic bags were brought inside.
Nevertheless, the team completed the mission, emerging into the outside world after two years of solitude in September 26, 1993.
"What was weird was actually coming out of the Biosphere," Poynter explains. "We’d been in there for two years, we’ve recycled everything, we know where all our food comes from, and all of a sudden it smacked us in the face the day we came out.
"The first thing that happens is I’m dying to see all my friends and family, and I run over and I give them a big hug. And then I pull away in disgust because we all stink out here. We stink of chemicals.
"But," she continues, "you get over that pretty quickly.
"The second thing was we had a party that evening and we had a bunch of people over. I walk out the next morning and there is this gigantic pile of garbage. And we hadn’t had any garbage in the biosphere, we recycled everything. And then you go to a store to buy stuff, and you’re like ‘holy cow, look at this’.
"There’s not only tomato ketchup, there’s like 17 brands of it! And look at the cheese from France!
"You look at all these pastries and you want to throw yourself in there, and just roll around because it just looks so scrumptious. You know it’s like, the abundance of this world, that we all take so for granted became so apparent [after B2]. It really smacked me in the face when we came out."
"It also became apparent how difficult it is, truly, to live that kind of lifestyle we were living in Biosphere 2."
I ask Poynter how many of the habits she adopted in the Biosphere have remained in her life. She pauses, contemplating, then tells me: "Mostly I try to live a life with as low a carbon footprint as possible. But I certainly think about it a lot."
If anything, Poynter says life inside the closed ecosystem taught her the value of food. One experience, in particular, sticks in her mind.
"How do you make a pizza?", she asks me, before answering the question herself: "You pick up the phone, you say ‘hey, I want a pizza’, a few minutes later, you get your pizza.
"In Biosphere 2, we would have to plant the wheat, which would take about 120 days to grow, so there’s four months right there.
"And then we’d harvest the wheat, grind the wheat, turn it into flour, and turn it into the dough for the bottom. That’s just part of it, now you’ve got to put everything on top of it.
"In order to get the cheese, it doesn’t just fall out of the sky. We had to have goats, that have been inseminated, have had kids, so now they’re giving milk, we take that milk and we turn it into cheese, and then every now and then the goats have to keep giving birth, so they keep giving milk." She pauses for breath, before summarising: "That’s the cycle, that’s why it takes so long, because you have to get the goat pregnant in order to make your cheese."
After a pause, Poynter laughs, adding: "I have to admit, pizza’s not my favorite food. I actually really missed chocolate."
Regardless of what went wrong in the experiment, the mission taught the crew members the fragile relationship between humans and their environment.
"One of the most extraordinary experiences was when you are enclosed in a system like that, it really is like planet Earth, it’s in miniature.
"And on a day by day basis I was very aware that the Biosphere, the plants, the algae in there, were providing me with my oxygen, and I was providing them with their carbon dioxide. It was this incredible interdependency. It's like that on planet Earth, but it’s so big you don’t realise it, or think about it."
The two years were also a fascinating glimpse into human behaviour, into what happens when people are forced to cohabit in a confined area.
"A lot of studies have been done on that," Poynter says. "If you have a small group of people you have to be careful who you choose. It was really interesting, we did have issues when we were in there but it’s the same kind of issues people have in the Antarctic, or the space station, things like that.
"There’s a constellation of things that occur in isolation and confined environments. What’s really fascinating, and I’d love to see studies done on this, is I wonder how much that is based on Western society and the way we think.
"Because the second crew had exactly the same kind of issues as we did, they broke up in warring factions, people had a bit of depression.
"But there was one person from the Himalayas, he was Nepalese, and could not understand what all the fuss was about. He had grown up in a small village, cut off for parts of the year, so people had to learn to get along.
"It’s a very different way of being in the world. I thought it was really fascinating. It’s anecdotal, not exactly an experiment, but fascinating nevertheless."
I ask her whether she would ever go back for another mission and she answers without hesitating.
"Oh yes, if there was a real reason.
"For many years I’ve been extremely excited about the notion of exploration in other planets. Not to leave the planet, but to expand from the planet. And that’s incredibly exciting to me. So sure, for that kind of thing, I absolutely would."
Jane Poynter was speaking at the first One Young World expert event, which focused on the environment and allowed young leaders to come together with world experts to create solutions to tackle one of our most pressing global problems.
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