10 July 2017

Apple trees won't bloom on Mars

Mars: more deadly than we thought

Julia Korowski, XX2 century

Let's see how you now grow potatoes on Mars

In March of this year, scientists simulated Martian conditions on a balloon and showed that contamination by terrestrial bacteria does not threaten Mars – because of UV radiation, they simply do not survive there. A group of researchers from the University of Edinburgh approached the issue from the other side: they claim that the soil itself is harmful to the microbes known to us and confirm this with numerous experiments. The results of the work are published in the journal Scientific Reports (Wadsworth & Cockell, Perchlorates on Mars enhance the bacteriocidal effects of UV light).

The authors of the study were interested in one of the components of the Martian soil – salts of perchloric acid, known as "perchlorates". For the first time these compounds were discovered in 2008 with the help of the Phoenix lander, later their presence in the soil was confirmed by Curiosity and Mars Reconnaissance Orbiter. It is thanks to the perchlorates on There is liquid water on Mars – these salts significantly reduce its freezing point. Perchlorates are toxic to humans, but they do not pose a danger to microbes and can even serve as an energy source for them at room temperature or lower. Or at least that's what it used to be.

Scientists from the University of Edinburgh have shown that hydrochloric acid salts are harmful to microorganisms if ultraviolet radiation comes into play. They conducted experiments involving the hay stick (Bacillus subtilis) – aerobic soil bacteria that love to settle on spacecraft. First, the microbes were placed in a liquid solution, magnesium perchlorate was added to it in concentrations found on the Red Planet, and exposed to UV rays. After 30 seconds, all the cells died. Bacteria from the control group, which were fried under ultraviolet light, but without extraneous chemical compounds, lasted a whole minute.

Because the water on Mars is the exception rather than the rule, the researchers tried to simulate a rocky environment and in the course of the next experiment, a silicon dioxide disk was used instead of a solution. This time the cells were more fortunate, but perchlorate still reduced survival: nine times, while UV radiation – only twice. The bacteria were then exposed to other factors of the Martian environment, individually and in combination. When the hay stick was deprived of oxygen in addition, the cells died in a minute, and at a temperature of 4 degrees Celsius, the microbes in a liquid solution lasted three.

The situation was no better with other salts of perchloric acid – calcium and sodium perchlorate. They reduced the number of bacteria almost twice, even when the UV light source was 4 times farther away and the radiation level was 16 times lower. Finally, the scientists added two other compounds that are found in Martian soil – hematite and hydrogen peroxide. In combination with perchlorate and simulation of solar radiation, they gave the most deadly effect. Scientists explained this by the fact that a Fenton reaction occurs between hematite and peroxide, which is fatal for microorganisms.

Scientists believe that at the moment the surface of Mars has a detrimental effect on microorganisms. Even liquid water is harmful to cells if it contains perchlorates. However, this has its advantages: the risk of inadvertently bringing terrestrial microbes to the Red Planet is very low. The authors conclude that the aquatic environment of Mars is "potentially less habitable than previously thought."

Portal "Eternal youth" http://vechnayamolodost.ru  10.07.2017

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