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SO ENDS this first of two weekends on an interesting paper suggesting that some planets may support life driven by galactic cosmic ray metabolism as a surrogate for photosynthesis. Biology has been too fixated on “life as we know it”. Different thinking is required to search for life as we do not know it. The extraordinary forces of the turbulent cosmos mean that both physics and chemistry will be quite different, and the types of molecules produced will not resemble Earth chemistry. In turn, this direction will inevitably lead to a better working definition of what life is, required if we are serious about searching for it in the cosmos. View in LinkedIn

FREE RADICAL QUENCHING. “The authors concluded that melanin played a major role in protecting the organism against ionizing radiation and these radioprotective properties arise due to its chemical composition, free radical quenching and spherical spatial arrangement.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

MELANIN PROTECTION MECHANISM. “Ionizing radiation changed the electron spin resonance signal of melanin, making it more efficient in acting as an ionizing radiation transducer. Experiments have shown increased metabolic activity in melanized Cryptococcus neoformans relative to non-melanized ones, indicating the enhancement of the electron transfer properties of melanin.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

SPACE STATION BUGS. “The presence of several microorganisms has been studied in the Russian Mir Space Station as well as the International Space Station. The organisms consist of both bacteria and fungi, and are exposed to about 4 cGy of ionizing radiation per year. Many bacteria and fungi in these environments have been found to be pigmented or melanized.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

THRIVING ON RADIATION. “Radiotropism is a term used to describe the growth of fungi from exposure to radionuclides. Most radionuclides emit beta (electrons and positrons) and gamma (photons) radiation and studies have shown that exposure to both sources promoted directional growth of fungi. Exposure to 121Sn and 137Cs sources showed that the spore germination in species increased considerably, a phenomenon also known as ‘radiostimulation’.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

MELANIN PROTECTION. “It has been found that the action of proteins is primarily responsible for the repair mechanism. An abundance of highly melanized fungal spores in the early Cretaceous period deposits has been uncovered, where other plant and animal species have died out. These types of fungi can be found in high-altitude terrains, Arctic and Antarctic regions, and in the Evolution Canyon in Israel.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

OTHER RADIATION EXTREMOPHILES. “Deinococcus radiodurans has a specialized recombination system for DNA repair from ionizing radiation. Interestingly, many fungal species also have very high radiation resistance. Many fungi have 10% survival chance or LD10 values exceeding 5 kGy. Other species, such as Ustilago maydis are also known to have extreme radiation resistance but have a different mechanism to cope with compared with radiation D. radiodurans. For comparison, mammals have very low radiation resistance and a dose between 5 and 10 Gy is lethal.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

TOLERANCE TO NUCLEAR RADIATION. “Exposure to high environmental radiation dose also leads to substantial energy expenditure in repairing radiation-induced damage. Bacterium Deinococcus radiodurans is the focus of numerous studies and is the most radioresistant microbe with a lethal dose (LD10) at 15 kGy.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

SURACE DESTRUCTION. “Energetic particles are capable of destroying organic materials present in the surface or subsurface environment of planets with thin atmospheres. A number of studies have been devoted to studying the impact of Galactic cosmic rays on the possible destruction of organic matter on Mars. Mars' surface radiation dose is several orders of magnitude higher than that of the Earth due to its thin atmosphere.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn

DEEP PENETRATION. “If a planet lacks an atmosphere, particles are able to directly strike the surface and the cascade of secondary particles is able to propagate underground. The secondary particles produced in the cascade, such as pions and kaons, are highly unstable, and quickly decay to other particles including beta particles (electrons and positrons) and gamma rays. It must be noted that beta particles and gamma rays are also produced during radioactive decay in underground rock. When charged pions decay muons are produced, and these can travel several kilometres deep depending on their energy.” https://royalsocietypublishing.org/doi/10.1098/rsif.2016.0459 View in LinkedIn