State of the art of world science allows scientists to talk only about time when life appeared on our planet, but not about life’s place of origin, head of the Institute of Paleontology, full member of Russian academy of sciences Alexei Rosanov believes.

The scientist thinks that probability of Earth being the place, where the life had appeared, is negligibly small. The history of our planet consists of two periods: first lasts since the moment of Earth’s formation (4.6 billion years ago) till about 4 billion years ago, when life is believed to appear, and second – earlier than 4 billion years ago. First period is notable for numerous meteoritic bombardments and almost no water on Earth’s surface, which made colonization and expansion of microorganisms over the planet impossible.

Temperature of ancient Earth’s surface hadn’t been very high, researchers say, and it is no wonder. Melted matter with temperature of several hundred degrees Centigrade can easily be isolated by a crust of cold rocks as thin as several tens of meters. People build houses in areas with active volcanism, where rocks at small depths are very hot – hundreds of degrees Centigrade.

 

 

Sedimentary rocks, as well as water, had appeared on our planet about 3.85 billion years ago. Some think that meteoritic bombardments had been responsible for removing water, which could have appeared on Earth’s surface by some means. Well, since that time the amount of water of Earth had been growing very fast. Shallow water basins boiled with microbial life. Oxygen appeared is atmosphere of our planet 3.5 billion years ago. About 2.2-2.5 billion years ago concentration of this vital gas became sufficient for microbes to leave water and colonize the ground. Bacteria and probably fungi could then live on planet’s surface. Multicellular organisms (Metazoans) were spotted in various pieces of water about 1.6-1.4 billion years ago. 1.3 billion years ago our planet had almost the same amount of water we have now, and since that time living organisms started a massive expansion. Higher plants had appeared on Earth 400 million years ago, and today we have almost the same planet, excluding changes in climate, sea and glacier configurations and etc, of course.

And what about meteorites? Some celestial bodies, which reached surface of our planet, are 4.5-4.6 billion years old, and they contain carbon substances of complex nature. Electron microscopy helped researchers to notice remains of microorganisms in meteorite organic matter> these microbes were so closely tied to mineral components, that their terrestrial origin is at least questionable. These ancient microorganisms are considered to have arrived from outer space, because they are older than meteorites, which carried them, and even older than our planet.

Studies of microorganisms, found in permafrost of Siberia and Arctic ice demonstrate that many species of tiny organisms are able to be dormant (in anabiosis) for millions of years, thus can possibly survive a long journey in space or nuclei of ice comets.

Therefore, Russian paleontologists strongly believe that life was never “born” on Earth. First Earth dwellers had most likely appeared in space and then arrived on Earth and spread all around the planet, when favourable conditions formed.

Source: Science News

Kizilova Anna