NASA’s most advanced rover to date is currently on its way to the Red Planet, where it will attempt to land next week. And, if all goes to plan, after the reddish dust settles, the Perseverance rover will roll down dry riverbeds in a first direct attempt to answer the question at the heart of most Mars exploration programs: Is there life there? Or at least was she ever there?
Persistence is unlikely to give us a definitive answer to these questions in the near future, but as the results of his work return to Earth in the coming years, some planetary scientists will look in them for hints of an even more fantastic idea. The idea that life on Earth came from Mars.
“There are some things that have come out quite recently that strongly support at least the plausibility of the hypothesis of the origin of life on Mars and its potential transfer to Earth,” says Christopher Carr, a planetary scientist at the Georgia Institute of Technology, who recently published his work with an overview of this theory.
In recent decades, biologists have reconstructed vast stretches of the family tree that links all known organisms. The fossils suggest that humans and apes had a common ancestor just 13 million years ago, while whales, bats, and humans approximately 65 million years ago. The last universal common ancestor, the microbial Adam or Eve, probably lived in warm water near an underwater volcano about four billion years ago, genetic studies have shown.
All groups of living beings on Earth. We are at the top right.
And then the trace is lost. Detailed genetic records disappear at the base of the tree of life. It is possible that the universal ancestor may have had competitors for some time, and they could have remained in the form of fossils, but plate tectonics on the planet has long destroyed most of these earliest rocks. All we know is that the Earth was formed about 4.5 billion years ago, and half a billion years later, the common ancestor of all organisms lived. How it developed and where its predecessors came from remains a matter of controversy.
There is a fairly well-developed theory of panspermia, which claims that life can be transported through space on asteroids – and this is not particularly surprising, given the fact that there are enough bacteria that can easily withstand the harsh conditions of space for several years. Carr and several other scientists have developed this theory further: according to them, perhaps the common ancestor was a descendant of microbial “Martian invaders” who flew to us on the so-called asteroids from Mars. This assumption, of course, has not received widespread acceptance, but Carr puts forward two curious reasons that make us think about the Martian origin of life.
Organic molecules are “found virtually everywhere” in the universe, he said. But no one knows in what kind of chemical reactions they merged into various building blocks necessary for the “assembly” of cells on Earth. One hypothesis is that the friendliest environment for “preparing life” is element-rich land in shallow water, where ultraviolet light and heat from volcanoes or asteroid impacts can properly mix the ingredients.
However, the early Earth was literally drowning in water. According to researchers, three and a half billion years ago, the entire surface of our planet, with the exception of a couple of percent, was deep under water, and the universal ancestor lived long before that. Meanwhile, simulations show that young Mars was humid, but there was still plenty of land on it, which offers much more room for life to begin.
The second reason is even more interesting and lies in amino acids – the building blocks that cells use to construct proteins that are essential for life. All descendants of a common ancestor create their molecular mechanisms from the same 20 molecules, although most modern proteins can presumably be created from half of this repertoire.
But why do we need the rest of the amino acids? Study 2018 shows that they help organisms cope with oxidation (because the oxygen we need for life is a fairly strong oxidizing agent). And, since the common ancestor had these amino acids, we can conclude that its predecessors evolved in an environment rich in oxygen or other oxidizing compounds.
But the Earth was anoxic for the first 2 billion years. That is, the universal ancestor in his habitat simply did not need “antioxidant” amino acids. Where did they come from then? The roots of his family tree, Carr suspects, may go to Mars, where oxidative conditions arose earlier than on Earth. Once there, life could have entered Earth on one of the many asteroids that were exchanged between the two planets.
However, other researchers doubt that the problems of the origin of life on Earth are serious enough to resort to interplanetary travel. Yes, there were no continents on the young Earth, but according to Nicholas Hud, a biochemist at the Georgia Institute of Technology, there were enough islands like Hawaii that were probably more than enough for life to arise.
Something like this might have looked billions of years ago, the Jezero crater – the place that the new rover will study.
Moreover, many scientists believe that life originated at the bottom of the oceans, next to the deep-sea vents of volcanoes: they eject many necessary elements from the bowels of the Earth, and besides, it is warm there. Finally, Hud suspects organisms may use additional amino acids for reasons other than oxidation.
Several researchers over the years have argued that Mars was once a more favorable environment for life than Earth, but Hud has not yet found one that he finds convincing. “I believe [перенос источника жизни на Марс] too dramatic, ”he says. “Perhaps we just need to better understand chemistry. Maybe our early Earth model isn’t as good as it should be. “
The Perseverance rover will certainly not find signs of life on Mars next week immediately after landing, but its observations will at least begin to help researchers refine their understanding of the Red Planet’s past. As the rover explores Jezero Crater, which was carrying muddy river water from across the surrounding valley, its instruments will help better determine when Mars began to rust (or oxidize) by analyzing surface sediments (thereby checking which came first). a common ancestor on Earth or possible Martian life began to adapt to a new environment).
Carr is a member of the MIT Search for Extra-Terrestrial Genomes project, which is working on a gene sequencer, and he says that after years of development, their device is approaching flight readiness. The gene sequencer is used to detect genetic material and “decompile” its code. But, of course, the chances of discovering microbial life on Mars thanks to Perseverance’s capabilities are extremely low – especially when you consider that relatively favorable conditions on the modern Red Planet are found only deep below the surface.
However, Carr still hopes that his device will eventually land on Mars. “It can really be done as part of a future mission,” he says.
Source: iGuides.ru by www.iguides.ru.
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