In 2016, our understanding of Mars deepened significantly, thanks to a caravan of successfully launched rovers, rovers, orbital and ground missions.
We have compiled a complete and detailed map of the surface of Mars; we traveled more than a marathon distance across the planet, finding meteorites, craters, dunes and frozen water along the way; we have seen mysterious “vents” rich in methane; saw salty streams of liquid water on the surface and dried up river beds.
And what is most interesting, we found "Martian blueberries": hematite beads, which on Earth are produced by organic processes and living things in the aquatic environment. Considering how “earthly” the past of Mars could have been, we are still tormented by the question: is there, was or will there be life on Mars?
40 years ago, the Vikings twins were one of mankind's most ambitious missions to explore the Red Planet. They both arrived on Mars in 1976, a year after launch, during precise synchronization of the orbits of Earth and Mars. Orbiters were created to compile the first complete map of the surface, to find solid evidence of Mars' watery past. Viking 1 landed on July 20, 1976, and Viking 2 followed six weeks later. We first learned what the surface of the Red Planet looks like, and we sat with this data right up to the 1990s.
The most interesting thing about these missions was that, together with them, scientists set out to conduct three experiments aimed at finding life. If even one were positive, we would ring the bells and open champagne: there is life on Mars!
These three experiments were:
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1. Gas Chromatograph - Mass Spectrometer (GCMS), which was supposed to heat the soil to different temperatures and measure molecules that take on a gaseous form. He could measure a wide variety of molecular constituents with densities of up to a few parts per billion.
2. Gas Exchange (GEX) - During this experiment, the Viking took a sample of Martian soil and replaced the Martian atmosphere with helium, an inert gas. Then they were exposed to nutrients and water: this is how scientists looked for signs of biological activity, such as the absorption or release of oxygen, carbon dioxide, nitrogen, hydrogen and methane.
3. A third experiment, labeled release (LR), took a sample of Martian soil and applied a drop of nutrient solution to it, in which all nutrients were labeled with radioactive carbon-14. Radioactive carbon-14 would then be metabolized into radioactive carbon dioxide, which would only be detected in the presence of life.
A control experiment - pyrolytic release (PR) - was conducted to ensure that any positive test was biological and not chemical in nature.
The first experiment was carried out first and was unsuccessful. Then there was the second, and again to no avail. When the third experiment began, the outlook was bleak, but data was collected anyway. To the surprise of many, both Vikings found metabolized radioactive carbon-14 in the carbon dioxide released. They even examined their samples from different locations: one from the soil in direct sunlight, the other from the soil beneath the rocks. In both cases, carbon dioxide emissions were instantaneous and constant after the first injection. To thunderous applause, the group, led by Gilbert Levin, decided they had discovered the first signature of life on Mars.
With bated breath, the scientists watched the control experiment - and it was then that everything became too suspicious. Subsequent injections of radioactive substances produced no response; what he saw was consistent with either organic or purely chemical inorganic processes. Perhaps there was no life on Mars. Despite the initial claim - if one of the three experiments is positive - we were unable to declare life on Mars because our results were inconsistent. Forty years have passed, and we have not repeated this experiment. We still don't know what the Vikings found.
In 2008, the Mars Phoenix lander discovered perchlorates in the soil, which could be the reason for the first positive result in the LR experiment. When heated, perchlorate can - in the presence of certain chemical compounds - produce chloromethane and dichloromethane, the very compounds that Viking-1 and Viking-2 discovered. But were those chemicals organic in nature or inorganic? Were they produced biologically or non-biologically? As it turned out, both options are suitable: the Martian soil, exposed to intense ultraviolet radiation, could produce these compounds without any life; and biological life forms could be responsible for this.
Forty years ago, a spacecraft from Earth first landed on the Martian surface on its own to find life. One of the experiments gave a positive result - and they are still trying to comprehend it. But the question of whether there is microscopic life on Mars is still open and remains unanswered. This question could be answered by a manned mission to Mars. The value of human ingenuity is still higher than robotic precision. Perhaps in the next ten to twenty years we will finally find the answer to the most important question raised by the very first Martian laboratory.
ILYA KHEL