Collins is subsisting largely on potatoes because he is isolated in a 24-foot by 44-foot greenhouse/apartment, a complex known as "Mars Base Zero."

He has been inside Mars Base Zero, a Quonset-hut shaped structure partially covered in Visqueen, since Sept. 17. He plans to spend at least 30 days and as long as 60 days inside the base, gathering all of his food from the 864 square feet of growing space inside.

A site off Goldhill Road is not exactly the surface of Mars, but Collins, 46, says the idea is to see how much greenhouse space it takes to support an individual over a given period and what are the best things to grow if it is your only food source.

He is drawing nearly all of his calories from potatoes and finds that he has to eat 3.5 pounds of food a day, enough for about 1,400 calories.

His stay at the base is part of the preliminary research for a study of how humans can live on Mars, a topic that has intrigued Collins and the other members of the International Space Exploration and Colonization Co. for years. They formed the nonprofit organization in 1988 in Fairbanks and began work on the base in the late 1990s.

There are about 20 active contributors to ISECCo, about two-thirds of them in the Fairbanks area.

They are trying build the knowledge base needed if humans are going to colonize other planets. Mars Base Zero has cost about $30,000, Collins said.

"I'm keen on space and I'm keen on living in new environments," explained Collins, speaking on the phone from inside the base.

"We're doing the best science we can with the resources we have available."

He's not actually locked inside, but there is a ribbon stapled outside the door of the compound, symbolically closing him in for the duration.

He has seen his wife Frankie and his 2-year-old son Richie, but they are separated by the Visqueen barrier. Frankie is expecting a baby in December, so Collins said that gives him an outside deadline to end his experiment in time to spend the last month of the pregnancy with her.

Collins said the only other thing that might cause him to cut his stay short is if there is a heavy and wet snowfall, which would collapse the Visqueen that covers the south half of the greenhouse.

"My anticipation is that I'm going to start running out of food in another three or four weeks. When the diet gets inadequate, that will drive me out," he said.

The base is not entirely sealed from the Outside world as he is able to get water through a hose and relies on air from the outside and heat from an oil-fired furnace, as well as electricity and a telephone.

This is the second time he has enclosed himself in the base. The first time was for a week in 2002 when he lived entirely off the land as a test.

Collins is living in a 200-square-foot apartment that features a loft, kitchen and a propane stove, on which he prepares potatoes and the other foodstuffs gathered from the garden.

He said it turns out that for Interior Alaska, potatoes are the most efficient crop as a food for humans. He is also eating carrots, tomatoes, spinach, lettuce, beets, turnips, cabbage and onions growing since the spring inside the greenhouse.

He has his computer and access to the Internet, which consumes a lot of his time along with reading and chores in the greenhouse.

Collins said many of the recipes he has been getting for new ways to eat potatoes are fine, except they rely on spices and oils, and he doesn't have anything to add to them, except parsley.

The idea, remember, is for him to be self-sufficient for everything except air and water.

"I'm feeling fine," he said the other day. "When I get a little tired of potatoes, I don't eat as much and by the next day I'm real hungry, so I eat some more," he said.

"My total calorie consumption goes up and down depending on how many potatoes I eat," he said.

Collins said he tried growing wheat inside the greenhouse and found that it took up a lot of space and produced about a cupful of food in the space that would produce about 10 to 15 pounds of potatoes.

The long-term goal of his organization is to build an underground airtight domed structure called Nauvik, where air will be recycled and all foodstuffs will be grown, he said. The utility bills in that structure may run $5,000 a month, so it will be a much more ambitious project.

He said he hopes through Mars Base Zero to learn more about how to adapt crop-growing techniques so they will work in an underground setting, completely closed off from the outside.

Collins is the brother of Miki and Julie Collins, the writers/trappers who live at Lake Minchumina and whose lives are an ongoing test of a different approach to survival.