By the time astronauts reach Mars will they forget why they are there?

A recent study argues radiation exposure en route to Mars may cause the mission crew to develop brain damage.

“What happens to your brain on the way to Mars”, a paper in Science Advance, by a group of radiation researchers, reports memory loss to mice caused by administering very large doses of galactic cosmic ray (GCR)-like high-energy radiation. They contend that long-term galactic cosmic ray exposure leads to dementia-like cognitive impairments, with serious implications for human Mars explorers.

The lead author of the study, Charles Limoli of the University of California Irvine, adds in a university press release:

The researchers found that exposure to these particles resulted in brain inflammation, which disrupted the transmission of signals among neurons. Imaging revealed how the brain’s communication network was impaired through reductions in the structure of nerve cells called dendrites and spines. Additional synaptic alterations in combination with the structural changes interfered with the capability of nerve cells to efficiently transmit electrochemical signals. Furthermore, these differences were parallel to decreased performance on behavioral tasks designed to test learning and memory.

However, Mars mission crusader Robert Zubrin challenges several components of the study in “Debunking the invalid claims of a space radiation paper” in The Space Review.

The four-millionfold difference in dose rate between the lab study and spaceflight is of critical importance. It is a well-known finding of both chemical and radiation toxicology that the effects of large doses of toxins delivered suddenly is entirely different from the effect of the same amount of toxin delivered in very small amounts over a long period of time. The difference is that the body’s self-repair systems cannot deal with a sudden dose, but can easily manage the same dose if received over an extended period. For example, if an individual were to drink one shot of vodka per second for 100 seconds, he would die. But if the same person drank one shot of vodka a month for 100 months, he would experience no ill effects at all. This is about the same ratio of dose rates as that separates the invalid work reported in the paper (1.6 rad per second) from what astronauts would actually experience in space (1 rad per month.)

It is shocking that the authors neglected to caveat the significance of their results by admitting these differences. Not only that, they kept the information about actual dose rates employed buried deep within the paper (it can be found in the middle of a text paragraph towards the end entitled “Animals, heavy ion irradiation, and tissue harvesting”), thereby allowing it to easily be missed by popular science writers duped into reporting the allegedly sensational implications of their irrelevant work.

But one commenter on the article asked, if the study is as bad as Dr. Zubrin states, why did NASA recently give these researchers $9 million to follow up on their work?

[Thanks to Martin Morse Wooster for the story.]