Prolonged life in space en route to Mars will make the ship's crew more prone to panic attacks and amnesia due to how cosmic rays will affect the transmission of signals in their brains. Scientists who have published the results of experiments on mice in the journal eNeuro write about this.
In recent years, doctors have been actively studying the consequences of prolonged stay in space for the human body. Most of these studies were carried out either aboard the American shuttles, or directly on the ISS, as well as aboard a number of Russian biosatellites. Scientists managed to uncover a number of health threats to future Martian colonists or deep space explorers.
Thus, experiments on fruit flies have shown that long life in zero gravity leads to a weakening of innate immunity and makes insects vulnerable to fungi, and also disrupts the readability of a number of genes. In addition, life in space accelerates the aging of the bone marrow, inside which new immune cells are formed, and prolonged bombardment of the brain with cosmic rays irreversibly lowers IQ.
Statements of this kind, as the researchers note, often cause a lot of controversy, since scientists are not observing the real effect of cosmic rays on the brain of humans or other mammals, but very powerful beams of heavy or light ions or other accelerated particles that imitate their action.
Discussions are fueled by the fact that different groups of experimenters often come to opposite conclusions, using the same types of particles, but in different doses or irradiating animals in different ways. All this does not allow us to give an accurate assessment of exactly how radiation will affect the brain health of the ISS crew and future lunar or Martian colonists.
Limoli and his colleagues tried to eliminate these discrepancies by placing the experimental animals in conditions as close as possible to those in which future marsonauts will live on their way to the red planet and on their way back to Earth.
To do this, they calculated what types of cosmic rays would most strongly affect them, and created a special emitter based on radioactive californium-252. The decay products of this unstable isotope turned out to be very similar to the stream of particles that will "bombard" the body of cosmonauts and astronauts during their flight to Mars, including in composition and in the strength of their action on the human body and the skin of the ship.
For the most part, as in the case of real rays, they will be composed of neutrons, one of the least studied components of cosmic radiation. Recent experiments by Russian space physicians have shown that these particles can slow down the formation of new cells in the brains of animals and affect their behavior if they are quickly irradiated with sufficiently large doses of neutrons.
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American researchers have checked whether these anomalies will persist at the "natural" level of cosmic radiation. To do this, they acquired several dozen mice, put them in a cage, which was continuously "bombarded" by their radiation generator, and observed changes in their behavior for six months.
As it turned out, in this case, the work of the brain of the mice, especially their hippocampus, the center of memory, and the amygdala, the main "conductor" of emotions, changed markedly. High-energy neutrons and photons, biologists have found, not only suppressed the formation of new nerve cells, but also changed the way existing neurons interacted with each other.
In particular, the radiation made the cells of the memory center less active and connected with each other, and also impaired their ability to form new bonds with neighbors. Similar changes took place in the amygdala and in the prefrontal cortex.
All these anomalies did not pass without leaving a trace for the mice - the rodents began to have memory gaps and they began to remember worse relatives they already knew, recognize new objects in the cage, look for a way out of the maze and solve other memory problems.
In addition, the mice suddenly became "social phobes" and began to constantly avoid contact with any other rodents, and also constantly experienced bouts of depression, panic, and other mental disorders. In particular, they less often left their nests, showed excessive caution, and were slower to forget about dangerous situations already experienced.
Interestingly, severe violations of this kind did not occur in all rodents - on average, neutron irradiation seriously affected the work of the hippocampus in every third mouse, and the amygdala in every fifth rodent. In a similar way, the researchers believe, they will affect people on the way to Mars.
All this, according to Limoli, suggests that mankind needs to understand how to protect astronauts and cosmonauts from the action of cosmic rays or suppress the effects that they generate before flying to Mars and other distant worlds of the solar system.
