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Biospace 21

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When I was a college student, in the late 1960s, I "wasted" time in my astronomy class making schedules of when humanity would achieve certain goals in space. First space station in orbit-1975. First mission to Mars, 1980. First colony on Mars, 2010. First unmanned interstellar flight, 2005. That sort of optimism was common then. Ever since, engineers have told the public and each other that these weren't unreasonable goals, that only politics prevented us from accomplishing the dreams revealed in the motion picture 2001: A Space Odyssey.

But they were wrong. It wasn't just politics. If we had tried to fulfill these optimistic timelines, it's likely that many astronauts would have died. The missions would have failed. But it wouldn't have been engineering in the strictest since that would have failed--it would have been biology.

In the 1970s, and even into the 1990s, biological knowledge was not equal to the task of designing a healthy space environment for long-distance missions lasting more than a few months.

Frank Poole and David Bowman, aboard the huge spacecraft Discovery, would have faced far worse enemies than Hal.

Imagine waking one morning to find that nearly all species on Earth have vanished. It's the greatest mass extinction the Earth has ever known. Not only have all large mammals (except for you) disappeared, but nearly all plants, most of the microscopic protists and bacteria, most viruses, all life in the oceans: Gone.

Gone are all the ecological support systems to which you and your living relatives have become accustomed over billions of years. No Gaia, no biosphere. Merely a few varieties of bacteria and viruses in your body, in the plumbing, on the walls of your dwelling. A few weeds in a tank. Frozen vegetables and meat in the freezer.

That's what will happen to astronauts traveling to Mars and the outer planets, or to the stars. They will be cut off from the main body of the Earth, like tiny severed limbs, hoping to carry their own supply of oxygen and nutrients for a long, long voyage. Not a cheery prospect.

We are all more intimately connected to Earth than most of us, trained in the reductionist biology of the late twentieth century, have ever imagined. Only in the last few decades have biological systems and the interaction of microbial life forms begun to be seriously studied--with fascinating results.

Fortunately for our ongoing hopes of living in space, research on biological systems in isolation and in microgravity is now speeding up. The Lunar-Mars Life Support Test Project (LMLSTP) Phase III has already finished a 90-day test with 4 crew members isolated in two chambers. Tests are also being conducted in a research facility called BIO-Plex, (http://www.spaceref.com/redirect.html?id=0&url=pet.jsc.nasa.gov/), where eventually, four hardy souls will be sealed off from the rest of the Earth for periods of up to eight months.

These experiments are not conducted in zero-g, however. It is hoped that research on astronauts in weightless conditions can be made to match up with research on people in isolated environments, an assumption whose correctness we are still too ignorant to judge.

NASA-funded space habitat and ecology research projects alone fill several pages on the web. While the majority of biological research still focuses (rightly so) on astronauts' reactions to zero-g environments, a substantial number of projects are examining the environments themselves. Space biologists such as Duane L. Pierson at Johnson Spaceflight Center and Barry H. Pyle of Montana State University, along with dozens of colleagues, are helping to increase our understanding of the potential dangers.

What we do know about people in isolated and weightless conditions is interesting and a little alarming.

First, the good news: On submarines, crews quickly dispose of all cold and flu viruses. Everyone gets whatever is available that they are not immune to, and in a few weeks, the reservoir of naïve hosts (where viruses mutate and plot new strategies) is tapped out. These relatively benign viruses run their course. But other viruses that linger inside cells for years or even decades are not so limited.

In microgravity, astronaut immunity is depressed, perhaps quite literally. Our immune systems behave much like separate brains, with their own chemical and biological senses, controlling the body's basic responses to the environment. Immune weakness could allow expression and transmission of latent hepatitis B and long-lasting herpes viruses such as chicken pox and Epstein-Barr. (Over nine out of ten people are infected by Epstein-Barr, also known as mononucleosis.) How such expressions and re-infections would behave in space, long-term, is largely unknown.

Stress increases virus release, however, and a spacecraft crew facing dangerous emergencies--or just long-term weightlessness--could suddenly find themselves flooded with latent viruses up to no good.

Bacteria seem to flourish in weightless conditions, which is easy to understand, given the nature of their medium. Water at their scale is like a very thick gel, and all their motions and chemical processes have to deal with this gel before they deal with the much less formidable effect of gravity.

Bacteria are masters at adapting in unexpected ways to new environments. If, under weightless conditions, they find themselves transported to places and situations where opportunity beckons--where tempting resources suddenly become available--they could change in ways we can't currently predict. (Imagine a spacecraft filled with highly motivated and creative microbes intent on filling every open ecological niche, engaging in a microscopic Cambrian explosion!)

Many bacteria--most famously, Pseudomonas aeruginosa--produce alginate, the polysaccharide main component of biofilms. Biofilms can form complex slime cities, both bacterial armor and architecture, that protect bacteria from detergents and antibiotics. Pseudomonas is frequently found in hospitals, causing severe infections in patients equipped with smooth plastic catheters--which support the growth of biofilms.

In many respects, a spacecraft is like a "clean" hospital interior, with many smooth surfaces waiting for bacterial or fungal contamination. Moisture, bits of skin, mucus, and hair--common in any human environment--could create ideal conditions for microbial growth. Drifting bacteria from zero-g waste disposal units--or floating free from astronaut skins or exhalations--could also cause problems. Astronaut sexual activity--and of course, astronaut injuries--could also release bodily fluids, with possible serious risk of cross-contamination. Aerosols of bodily fluids in space could protect viruses and bacteria for hours, or even days in some cases.

In microgravity, some pathogenic bacteria show a troublesome increase in resistance to antibiotics and detergents. Such bacteria, like latent viruses, may be more likely to attack and spread when their hosts are under stress.

And of course, space exploration produces unique kinds of stress in astronauts.

We can't simply clear astronauts of microorganisms. Many bacteria partner with us in digesting food, and even supply quantities of essential nutrients. Bacteria on our skin and within our body cavities--nose, urethra, vagina--help us fend off invasions of pathogenic relatives by sucking up all the available resources, and in some cases by fighting off potential enemies with microbiological warfare agents.

Nevertheless, some bacteria can become deadly at any sign of stress or weakness. Swapping genes for toxicity and virulence, they move in like predators to challenge and weaken, and perhaps even kill, their hosts. In a larger ecosystem, they are part of the eternal round of competition and cooperation which leads to dynamic balance. But in a limited and unfamiliar ecosystem, such as a spacecraft interior, they could fluctuate wildly and cause major problems. Bacteria appear to increase in numbers in the urinary tracts of shuttle and Mir astronauts in space, and that growth, in these vulnerable tissues, could result in severe infections.

We are ecosystems in our own right, and astronauts facing a personal, internal, eco-disaster in their intestines and urinary tracts could experience stomach cramps, severe pain while urinating, high fever, and much worse.

Growth of microbes in a spacecraft, without proper controls and balances, could lead to the equivalent of Sick Building Syndrome on Earth. Microbes produce many volatile gases, some of them irritants and allergens, and some highly toxic; after several months or years, such a "sick" spacecraft could weaken and even kill its astronauts.

Combinations of problems--a sick spacecraft stressing its crew, leading to increased expression of latent viruses--are particularly worrisome.

The story does not end with microbes. In a typical terrestrial environment, mites and insects such as carpet beetles help break down our dry waste products. Hair and skin flakes--typical food for a number of common household critters--will have to be kept under control in any spacecraft interior, and that means frequent vacuuming--but even so, a few stray animals could set up "housekeeping" operations in space. With them will come their own "fleas," specialized varieties of protists and bacteria. And these microbes will have to be monitored as well, for only a few will spend their entire lives inside their hosts.

Fighting these little creatures is ultimately going to be a losing battle. Our biological camp-followers are, most of the time, useful friends--and it's almost certainly going to be necessary and even beneficial to try to maintain and balance different ecological relationships, with different varieties of "scavengers" and microbes, for long space voyages.

Proposed robotic micro-scavengers and cleaning units, while feasible, will be expensive, difficult to maintain, and likely to be far less efficient at many tasks than their natural counterparts--but also more predictable. Until they become practical, however, the issue is moot.

Self-directing microbots are still found in only one ecological niche--the drawing board.

Our astronauts' problems do not end with proper ecological balance in and around their bodies. Waste products will have to be recycled and fluids recovered--storing them whole or discarding solids is both wasteful of energy and inelegant.

Ideal technology would allow 100% recycling of liquid wastes, with bio-reactors converting solid waste to food and even releasing nitrogen and oxygen to help recreate Earth's atmosphere. Missions of more than two or three years duration will very likely have to completely recycle waste products; ultimately, spaceships and planetary colonies will have to mimic Earth's biosphere.

Astronauts cannot afford to be squeamish. After all, sharing food and water is what Earth is all about--though with longer cycling periods.

Potentially the greatest problem of all is seldom discussed in public, and that is venting. Not the venting of astronaut gases--though that might be an annoyance in close quarters--but leakage of volatiles from the spacecraft. Seals technology may still be inadequate to the task of keeping volatiles within our ships for periods of more than a couple of years. The Mir space station needs frequent replenishing with volatiles, and so will the International Space Station.

For every few hundred grams of gas and water lost per day, travelers could face crisis or even disaster on a long journey.

A number of visionaries have propose private space ventures, performed with individual know-how and ingenuity the government and NASA can't match. Such missions could be quick and cheap--but they could also be quick, dirty and dangerous. If these ventures ever make it past the planning stages, the planning had better include a practical knowledge of spacecraft biology.

Anything less would be foolish. Death doesn't cut you some slack just because you're a rugged individualist.

(First published on www.Space.com. © 2000 by Greg Bear. This revision © 2001 by Greg Bear.)

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