Mars Mission Risk 29: Scientists Research Ways to Reduce Radiation-Induced Brain Damage

Research could lead to new treatments for conditions like Alzheimer's disease

September 27, 2006

Supernova explosions like this one accelerate atomic nuclei to nearly light speed. The resulting "cosmic rays" pose a potential hazard to astronauts. Photo courtesy Science@NASA.

NORFOLK—Among the gravest risks of a manned flight to Mars ranks the possibility that massive amounts of solar and cosmic radiation will decimate the brains of astronauts, leaving them in a vegetative state, if they survive at all.

Dubbed "Risk 29" by NASA's Mars scientists, the cosmic radiation risk remains a show-stopper because shielding a spacecraft from all radiation could make it too heavy to reach Mars, which, at its closest, is 38 million miles from Earth.

Now, medical scientists at EVMS have been tasked with determining the human brain's maximum safe cosmic radiation dose and to decipher precisely how radiation causes cognitive impairment — part of a quest for biological countermeasures to reduce radiation-related cognitive impairment.

The NASA-funded $1.2 million research project could not only help eliminate the risks to astronauts, but it could unravel the biomechanics of brain damage, potentially benefiting patients with degenerative neurological conditions like Alzheimer's disease.

"This research may not only help make it safer to go to Mars, it could lead us to a deeper understanding of how the brain functions," said principal investigator Richard A. Britten, Ph.D., associate professor of radiation oncology and biophysics. "That eventually could help patients dealing with conditions that cause dementia."

The idea of a manned mission to Mars has captured the imagination for decades. But flying to Mars, even without humans aboard, is a monumentally risky feat. Since 1998, the United States has completed seven Mars missions. Four of those failed when the Mars landers were lost on arrival.

As part of a new push to put a man on Mars, NASA has sketched out a roadmap laying out 45 risks to astronauts on a two-year space mission. Risk 29 addresses the fact that Mars astronauts will be bombarded by high-energy cosmic radiation — shielded on Earth by the atmosphere and the Van Allen Radiation Belts — that few medical scientists have studied.

"These are very obscure kinds of radiation that on Earth we would only see in the event of a nuclear disaster," said Britten.

While many assume that open space between planets is empty, it’s not, Britten notes. The dark realm between planets teems with cosmic particles generated by solar flares, supernovas and astronomical cataclysms dating to the Big Bang, particles that can pass through metal and human tissues, often with enough energy to shred DNA.
To make matters more complex, one possible trajectory involves flying around Venus and using its gravitational pull to sling the spacecraft toward Mars. That means flying closer to the sun, the source of powerful solar radiation.

"The sun is basically a big nuclear reactor," Britten said.

The scientists hope to determine how much shielding the spacecrafts and astronauts will need, and also develop other countermeasures that help to reduce radiation-induced brain damage.

The EVMS team consists of Britten; Larry Sanford, Ph.D., professor of pathology and anatomy; Gyorgy Lonart, Ph.D., associate professor of pathology and anatomy; Sylvia J. Singletary, D.V.M., department of physiological sciences; and Richard R. Drake, Ph.D., associate professor of microbiology and molecular cell biology.

To help determine the brain's maximum acceptable dose of solar and cosmic radiation, Britten's team must replicate the type of radiation astronauts will be exposed to in deep space. They then must calculate how much damage is caused by particles with various energy levels.

"There are only a handful of laboratories in the world where these kinds of high-energy particles can be produced," Britten said. His team will work closely with scientists at Brookhaven National Laboratory in New York.

As part of his $1.2-million segment of the study, the EVMS team will measure physical and behavioral changes in rats exposed to various levels of the type of radiation that Mars astronauts will encounter in space. They will also conduct proteomic analysis of portions of the irradiated brains to obtain more precise details about the biochemical changes.

To date, many scientists have suggested that reduced cognitive impairment results solely from the death of the brain's neurons. Britten believes other, more complex mechanisms are at work, processes that could be manipulated by NASA's medical staff.

In a very rudimentary sense, the brain can be likened to photo paper. Chemicals allow the photo paper to “fix” the images – in this case, the “images” can be visual, aural, tactile, sonic, emotional or intellectual, often connected. If the chemical stew gets out of whack, the images, dubbed engrams, don’t stick or become cloudy and indistinct.

"Once we understand what's not working, then maybe we can fix it," said Britten.

Because radiation damage is similar to the free-radical injury resulting from aging and certain neurological diseases, the research could lead to better treatments for conditions like Alzheimer's disease that cause progressive dementia.

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