For NASA a New Research Study May Alter Plans on Sending Humans to Mars

August 11, 2019 – A paper published on August 5th in eNeuro, a journal of the Society for Neuroscience, may throw cold water on humans venturing beyond the confines of low-Earth orbit for the foreseeable future. Until we have mastered new and faster propulsion systems to go to places like Mars, or until we have developed shielding to protect crews from exposure to cosmic rays, we will be sending humans into an environment that will likely produce “serious neurocognitive complications,” “impairments in learning and memory,” and other mental health issues.

This is the first study of its kind to “document the significant adverse consequences of space relevant radiation dose rates on the brain, and points to the heightened risks associated with NASA’s upcoming plans for travel to Mars.” It represents the combined work of researchers from the University of California-Irvine, Stanford, Colorado State University-Fort Collins, and the Eastern Virginia Medical School in Norfolk.

As I read the paper I was surprised not to see a reference to Artemis, the name of NASA’s current project to return to the Moon. A long-duration Mars mission was certainly mentioned. But in both cases humans will be equally exposed to heightened risk.

What is the concern? Energetic charged particles called ions that travel through space at sub-light speeds.

Why isn’t this a concern on the International Space Station (ISS)? Because as long as human crews are in low-Earth orbit, the Earth’s magnetosphere shields them from exposure to these particles.

NASA has been studying the impact of radiation on human space flight for a considerable time. During the Apollo program, astronauts from Apollo 11 through 17 received from 1.8 to 5.5 milligrays (mGy) of radiation based on their stays on the lunar surface. This is not a significant amount of radiation when compared to a typical head CT scan of approximately 50 to 60 mGy, or a scan of the colon, abdomen or pelvis at 15 to 20 mGy. But the other statistic to consider is time. In Apollo 11 exposure amounted to 21 hours and 38 minutes. In Apollo 17, it was 74 hours and 59 minutes.

Artemis plans to have humans operating on the lunar surface for weeks at a time with the eventual goal of a permanent habitat. And a trip to Mars using conventional chemical rockets is expected to take 6 months in transit outgoing and returning, with the addition of time on the Martian surface, probably a number of months to a year to ensure the planets are aligned to make transit home in 6 months. So if you take Apollo 11 statistics at 1.8 mGy for just less than 24 hours of exposure, and multiply it to 30 days at a lunar outpost, or at 18 months to three years in a voyage to Mars and back, the mGy count starts adding up.

And we are only talking about ions from background radiation in space, the cosmic rays. We are not taking into consideration a coronal mass ejection from the Sun that could increase the exposure to energetic charged particles in space dramatically. NASA describes ionizing radiation as “difficult to avoid” in space. These particles travel through the body and interact like “an atomic-scale cannonball.” And more like the ones made of scattershot that break up and spread when they hit a target causing collateral damage.

On the ISS the human crews are somewhat shielded by the Van Allen Belt, a protective magnetic field that surrounds the Earth and contains highly energized protons. That’s because the ISS is orbiting 408 kilometers (254 miles) above the Earth, well within the protective Van Allen Belt cover.

And even though the ISS lies well within the Earth’s magnetic protective shield, NASA and Roscosmos undertook a study in which each exposed one of their crew to a year in space. NASA’s guinea pig was Scott Kelly, a twin, whose brother Mark Kelly was also an astronaut. The ability to compare twins, one exposed to low-Earth orbit space, the other on the ground, was unique. Scott’s epigenomics was studied to see if long-duration exposure altered DNA. It did while in space impacting the genetic makeup of disease-fighting white cells. The effect lasted only for a short period after Scott returned to Earth. Other physiological changes Scott experienced largely diminished over time once back from the ISS, but it must be emphasized that this was a test of human adaptation within the bubble of the protective magnetosphere. The Moon and Mars won’t be nearly the same experience.

In the eNeuro paper, the researchers studied energetic charged particles that included both electrons and neutrons. They did this by simulating the space environment and exposing 8-month-old laboratory mice to irradiation dose rates of long-duration space flight outside the magnetosphere. The daily dose rate was low, 1 mGy. And the cumulative results equal to long-duration space missions identified “a wide range of hazards associated with chronic particle radiation exposures occurring at all levels of nervous system function.” Significant changes occurred in the brain’s hippocampus at the cellular level. This is the area of our brains responsible for learning and memory. And what was observed was changes to synaptic signaling.

In addition, the exposure to neutron radiation impacted the medial prefrontal cortex at the synaptic signaling level, altering the test subjects’ behaviour and mood. The mice also displayed dissociative learning responses to prior event exposures that would induce fear which at the brain examination level showed cellular changes to the amygdalae (there are two, one in each brain hemisphere) in addition to the hippocampus and prefrontal cortex. The amygdala is responsible for our emotions, survival instincts, and memory.

The researchers concluded that their tests represent:

“a realistic model of the risks associated with the low dose and low dose rate radiation astronauts will experience over the course of a deep space mission. While our electrophysiological findings provide compelling evidence that chronic, low dose and dose rate irradiation perturbs hippocampal and medial prefrontal cortex activity, our behavioral testing suggests that functional deficits additionally extend to the perirhinal cortex, amygdala and possibly beyond. The spectrum of behavioral deficits we observe in social avoidance, anxiety, impaired fear extinction memory, and difficulties recognizing location and object novelty, would clearly impair the abilities of astronauts needing to respond quickly, appropriately and efficiently to unexpected situations that arise over the course of a mission to Mars.”

Consider this. Mars has a very weak magnetic field and it is distributed unevenly across the planet. And as for the Moon, the field is practically non-existent. Any protection from energetic charged particles would come from the envelope of the Earth’s magnetosphere which at the distance of our satellite is significantly weaker. For human crews on these two spheres, it will mean building protected habitats (probably underground or buried) and limited time outside on the surface. NASA is even exploring how to create electrostatic shields (shades of Star Trek). And in a recent development, both NASA and Roscosmos are taking the mothballs off nuclear-powered rockets which could turn a 6-month trip to Mars into one lasting as little as 30 days.