George Bush has recently announced his intention that the United States will return to the moon - this time to stay. Finally, NASA has received much needed direction for future space missions. His critics predictably will focus on budget and timing concerns but, in my judgment, the most important issue is direction.

Now one can say with reasonable assurance that, sooner or later, man will return to the moon, for man already possesses the technological ability to get there.The average person has no awareness of the potential benefit of lunar conquest. We have, at most, 50 years of oil-based energy remaining on this planet. Five hundred feet beneath our oceans' surface lies a vast supply of methane gas in the form of methane hydrate - estimated to exceed our combined oil, fossil gas and coal reserves by many times, if we could but exploit it.

Helium 3 is the secret of a startling form of nuclear fusion capable of producing vast quantities of energy without radioactive waste. It has been estimated that one shuttle-load of helium 3 could meet the entire energy needs of our planet for several years. Even if the cost is a billion dollars or more a load, the payoff for our children is tremendous. Space is our destiny and this is the energy that will get us there.

To get to the moon we must venture beyond the electromagnetic shield of the Earth into dangerous waters, waters we have only just begun to chart. Therein lies our challenge. Beyond this shield we are subject to the full impact of cosmic radiation, lethal to life as we know it.

The Earth's magnetic field, a product of its liquid core, spreads from pole to pole like a giant belt, extending from 400 to 40,000 miles above the planet's surface. Trapped within this magnetic belt are charged particles, both electrons and ions, the nuclei of atoms stripped of their electrons.

Raining down on this electromagnetic shield are ions of both solar and galactic origin. Some 85% of these ions are protons, the nuclei of hydrogen atoms. About 13% are nuclei of helium, known as alpha particles, our next most common atom. The remaining 2% is composed of the nuclei of heavier atoms including oxygen, nitrogen and iron, all traveling at tremendous speeds and known as the "heavies". Those of galactic origin have been brought to near light speed by powerful events such as supernovae and have energy levels some 10,000 times those of solar origin.

Life as we know it developed within this protected zone known as Earth. Now, on the way to the moon and to Mars, we are beginning to venture out beyond our shield. Protection from these extraordinarily energetic particles will be an immense challenge for they pass through the walls of a spacecraft as if the walls did not exist. Their impact on the human body is quite predictable.

In 1957 David Simons in Operation Manhigh, using stratospheric balloons to ascend to altitude, exposed himself and his "crew" of black mice to the radiation environment at 100,000 feet for more than a day. His effort was rewarded by numerous hits registered by emulsion plates strapped on his arms and a colony of black mice that transformed into a startling "salt and pepper" several weeks after landing, attesting to the effectiveness of extra-atmospheric cosmic rays in causing DNA and protein change - an ominous sign to geneticists.

In 1971 when Apollo 14 was some 100,000 miles out on its journey to the moon, the crew became aware of curious light flashes, especially noted in the darker recesses of their spacecraft and during scheduled sleep periods. By then, the Earth had receded in size to that of a large marble held at arm's length and they were well outside our planet's protective shield. Because they felt fine and did not wish to upset "ground", the crew elected to make their report several days later on their return leg of the mission.

On the basis of this observation, "ground" was quick to realize the likelihood that cosmic radiation was responsible for this light flash phenomenon and quickly conceived the Biostack experimental packages carried on Apollo 16 and 17. These bioscience studies, in which emulsion plates sandwiched such specimens as bacteria, crustaceans and insects in various stages of development, helped greatly to reveal the flux and energy levels of these energetic particles zooming through the spacecraft walls with ease and demonstrated clearly the biologic consequences when hits occurred in susceptible tissues, especially during embryogenesis.

In 1973 "Bill" Pogue, commander of Skylab 3, was one of our first astronauts to experience the now infamous South Atlantic Anomaly (SAA) and attempt to measure its unusual radiation levels. Roughly over the Easter Brazilian coastline, our 400-mile high electromagnetic belt circling the Earth is pulled downwards by a mysterious force to within 100 miles of the Earth's surface. As a result, all spacecraft launched into a relatively high orbit such as our three Skylab missions must pass through this zone of intense radiation several times each day.

In attempting to quantify this anomaly by "keying into his mike" with each light flash for the benefit of ground, Pogue at times could not key fast enough to record all hits. From what we know today, each flash represented a cosmic ray hit to the visual cortex of the brain, just as a neurosurgeon can induce such retinal flashes by direct stimulation with a needle electrode.

Jerry Linenger, in summarizing his 6-month adventure with fellow cosmonauts onboard MIR in 1996, reported that at times during passage through the SAA, sleep was impossible. On some occasions he even tried moving his sleeping platform so as to reposition his head behind lead storage batteries and other places offering thicker spacecraft walls but little benefit was obtained and when finally the SAA was passed the flashes were temporarily over.

We do know that spacecraft walls as currently constructed present no significant barrier to galactic cosmic radiation. If an occasional aluminum atom within the spacecraft wall is hit by one of these cosmic darts, the result is a shower of secondary radiation within the cabin from "daughter" breakdown products of aluminum and associated gamma radiation.

From the viewpoint of a tiny galactic "ray" we are mostly vacuum. An atom of hydrogen, helium, oxygen or nitrogen with its central nucleus and orbiting electrons has a superficial resemblance to our sun and its planets in relative terms. Just as most wandering asteroids harmlessly pass through our solar system, occasionally we are hit, as evidenced by the recent Shoemaker-Levy impact on planet Jupiter and the scars of previous hits on our moon, Mars and even our own planet. Similarly, most cosmic radiation passes harmlessly through our atoms but occasionally one is hit.

It has been estimated that in 6-months of spacecraft travel outside the protective electromagnetic shield of the Earth, every cell nucleus in our body would receive multiple hits from proton radiation. One of every three cells in our body would receive at least one heavy ion hit (oxygen, nitrogen or iron) to its nucleus.

We must remember that cosmic radiation of galactic origin may have energy levels as much as 10,000 times greater than that of solar origin due to their near light speed. Cosmic ray hits damaging just one strand of our DNA are usually reparable by body cells. When double strand breaks occur the result is severely mutagenic and frequently beyond complete repair.

Heavy ions, especially those having atomic weights approaching that of iron, if of galactic origin, leave a virtual tunnel of destruction surrounded by a zone of ionic chaos as our normal sodium, potassium and calcium ions become disrupted. Even our muscle cells must struggle to repair such damage but what about our central nervous system, having no repair mechanism? In nervous tissue the damage must become cumulative, gradually building up scar tissue as vital functions are progressively eroded.

Those central nervous system functions originating in small discrete areas of the brain will be most susceptible to early compromise. The amygdyla and hippocampal areas having to do with memory, the substantia nigra having to do with dopamine production and muscle coordination and the pituitary gland and hypothalamus, having to do with endocrine functions and metabolism can be expected to be far more susceptible to early deterioration than more decentralized functions such as our prefrontal cortex. With our present level of shielding technology a very substantial loss of brain function during a 6-month trip to Mars can be predicted.

At this time we have very few options that are sufficient for a continued presence of man beyond Earth's geomagnetic field. Once on the moon we have the option of burrowing deeply into the lunar crust and that remains a likely mandate for our lunar colonies to come. For a trip to Mars, conventional shielding by increasing the thickness or altering the composition of spacecraft walls appears futile.

Radical new concepts are needed to give us the same protection from galactic cosmic radiation afforded by the Earth's geomagnetic field. Just as it seems mandatory to "design in" artificial gravity for future spacecraft, so must we design in cosmic radiation protection. NASA overcame an immense challenge to place man on the moon but the challenge of keeping him there will be far greater.

Duane Graveline MD MPH
Former USAF Flight Surgeon
Former NASA Astronaut
Retired Family Doctor