American researchers have found that microscopic fungi Cladosporium sphaerospermum can be a radiation shield. This property was confirmed in the experiment on the ISS: it turned out that the mushroom film thickness less than two millimeters may reduce the radiation flux almost by two percentage points. According to calculations, to bring Martian ionizing radiation to safe values, is enough to “shield” with a thickness of 21 cm. The results of a study published on the bioRxiv preprints.
Once outside of the Earth, man is exposed to significant radiation. For example, astronauts during the work on the ISS, on average, receive a dose of 144 mSv and member of the Martian expedition, this figure is the total for the year will reach 400 millisieverts. On the Earth’s surface radiation is much less intense: the average annual dose is 6.3 mSv.
Although the influence of cosmic radiation on health remains poorly understood, experts do not doubt that it must be protected. However, the formation of mechanical protective shields requires a lot of materials, while the volume of the payload, which can take into space, is limited.
The original solution to this problem was proposed by Graham Shank (Graham K. Shunk) and Xavier Gomez (Xavier R. Gomez). The first of them is now studying at one of the schools of North Carolina, and the second was enrolled in the local University. They noticed that some living organisms to successfully cope with the effects of radiation. Certain types of mushrooms even learned to absorb ionizing gamma radiation with the help of the pigment melanin and use it to produce their own biomass in the process of radiosintez. Among them Cladosporium sphaerospermum, some strains of which survive even in the destroyed Chernobyl reactor.
Shank and Gomez suggested that the layer of mushrooms can be a great antiradiation shield space travelers and Martian colonists. One of its main advantages is that mushrooms can be grown in place from a sample weighing a few grams, but not to carry a lot of supplies such as aluminum or stainless steel.
This idea allowed the researchers to win the competition for space innovation, and in December 2018 the colony of C. sphaerospermum went to the ISS. Within 30 days the Geiger counters recorded the flux of ionizing radiation through the two halves of the Petri dishes, one of which was inhabited by mushrooms, and the second was control (it was filled with agar).
A colony of C. sphaerospermum suffered a great freeze during the flight into orbit and to the ISS quickly began to grow. As soon as the mushroom layer becomes thicker, the radiation flow through it has decreased. During the first 24 hours the radiation level under the “mushroom” half of the Petri dishes was 0.5 percent lower than under control. However, by the end of the experiment, the difference increased to around two percent. The mushrooms were blocking only one side of a Geiger counter, so if they surrounded him completely, this figure could be doubled.
While the reduction in the radiation flux by a few percent may seem small, it should be noted that this result was achieved due to the mushroom thin films with thickness of 1.7 mm. According to calculations, in order to reduce the radiation flux on Mars to earth levels, you will need a mushroom shield thickness of 21 cm. According to the authors, to create the best mix the mushrooms with the Martian soil and watered periodically melt water from the polar caps. Another option is to create a composite material from the local soil, combined with the mushrooms allocated from the pigment melanin. For protection from radiation will be enough devyatimillimetrovy layer of such a composite.
Korean scientists have discovered a way to protect mice from radiation sickness. They demonstrated that nanoparticles of cerium dioxide with a surface layer of mixed oxide of manganese increase the catalytic activity against reactive oxygen particles — one of the indirect mechanisms of influence of radiation on living organisms. In the experiment, they increased the survival rate of mice after high doses of radiation to 67 percent.
Sergey Knee High