vilelasb2104skt — 2018-03-13 19:07:08 UTC

The Mystery of the Origin of Life
Many scientists have already given up on the idea that life is terrestrial exclusivity.
One of the most interesting theories says that life came off the Earth, on Mars or another planet farther away. It was brought here by wandering comets.
How did life come to Earth? This remains one of the great mysteries of biology. We know only the approximate date on which this occurred: about 3.5 billion years ago. Everything else is speculation.
In the 1970s, most biologists believed that life was a chemical event so unlikely that it would not occur a second time in the universe. Decades later, in 1995, Belgian Christian de Duve, Nobel laureate in Medicine in 1974, classified life as a "cosmic imperative" that should have appeared on every planet similar to Earth. By this biological determinism, "life is inscribed in the laws of nature". To prove this theory requires finding traces of it on another planet or even on Earth - the conditions existing here propitious to the emergence of life could even have been used several times. Confirmation depends on whether organisms other than all known living creatures are found.

Alternative forms of life would have been able to have developed and disappeared, leaving geological records of their existence. A metabolism different from what we know, for example, could alter rocks or form mineral deposits in an inexplicable way for the biology of known organisms. Organic molecules characteristic of other life forms would also be stored in old microfossils.

Another theory proposes that alternative life forms would have survived and would always be present in the environment, constituting a kind of "shadow biosphere." These organisms would not yet have been found simply because biologists cataloged only a tiny fraction of all microbes observed. But such identification does not promise to be easy. It requires genetic sequence analysis to determine the location of the microbe in the tree of life that groups together all known creatures. It should also be considered that all the organisms studied in detail until now share the same biochemistry and an almost identical genetic code. The methods used to study them detect life as we know it. Other techniques would be needed to discover a different biochemistry. Until then, a life of this kind, which is limited to the microbial kingdom, is unlikely to be noticed

How did life come to earth by João Victor Vilela