Extraterrestrial life undiscovered among us

Do aliens already live on earth?

The British astronaut Helen Sharman says they could live undetected among us. Perhaps in a microscopic niche, suggests an astrobiologist

Helen Sharman, the first British female astronaut and the first female astronaut to visit the Russian Mir space station in 1991, is a firm believer in the existence of aliens. In an interview, she also said that they might already be living among us undetected. It might well be that we just can't see them. So they could be a kind of ghosts, ghosts or angels that we do not perceive with our senses because they are fundamentally embodied differently.

The British astrophysicist and biologist Samantha Rolfe from the Bayfordbury Observatory took up this idea of ​​aliens that are imperceptible to us and, in an essay, considered how they could live on earth without our noticing them. First she addressed the difficulties of how life can be defined. There are more than 100 definitions, which also makes it difficult to search for aliens in space or to recognize them. If you don't know what you are looking for, your search is of course limited, especially if you limit yourself to life as you know it from Earth. And of course intelligent life does not have to look humanoid or anything like biological life on earth.


According to Rolfe, life as we know it is often defined as MRS GREN: movement, breathing, perception, growth, reproduction, excretion and ingestion of food. Others try to define minimum physical and chemical requirements such as: compartments, program, metabolism, catalysis, regulation, growth, reproduction, adaptation / evolution. You can see that there is no coverage, only a partial overlap.

In any case, Rolfe tries to take up Sharman's hypothesis and think about how it would be conceivable that non-earthly life could have already established itself without our noticing it. It is conceivable that aliens with a different biochemical structure live in a hidden biosphere. With a high probability, such life forms would be microscopic. Larger, unknown biochemical structures would of course not be invisible ghosts; one could see them even if one did not know what it was.

Of course, microscopes could also be used to detect tiny aliens. So why haven't they been found yet? Rolfe suggests that many microscopic life forms have probably not yet been discovered because only a small fraction of the bacteria can be cultivated in the laboratory. It is true that the DNA of non-cultivable bacteria can be sequenced, but then only life as we know it, i.e. with DNA, can be identified.

Silicon, which is also abundant on earth, is often suggested as an alternative biochemistry to carbon-based life. Silicon is similar to carbon, but it is heavier, is less able to form long chains and strong bonds and is solid and insoluble in water at terrestrial temperatures. Silicon-based life forms could have originated on other planets, but there is no evidence of this, and it would be difficult to discover such life forms that do not resemble life on earth.

Migrating life

As researchers have found out, meteorites contain the nucleobases adenine, guanine and uracil as well as amino acids, which are formed from the molecules hydrogen cyanide, carbon monoxide and ammonia in the presence of water. From this, RNA can form with the mineral Schreibersite, which can also be found in meteorites. The first life forms were probably based on RNA, only later life forms developed on the basis of DNA. It would be possible, as scientists have found out with simulations, that the basis for RNA organisms was created when splinters of meteorites with a radius of 40 to 80 meters hit ponds on earth.

Possibly new life could arise on earth in this way, such as the hypothesis of panspermia, while the existing life already comes from space, on the other hand, life could have developed on many stony exoplanets with oxygen and water. So it could well be that alien microscopic life has come to earth, if one does not believe that intelligent aliens have already visited the world or visit it with or without UFOs and kidnappings without us recognizing them.

And the consequences?

But so far the only life we ​​know is earthly life. Rolfe thinks that as long as we do not know that there is life elsewhere in the universe, we should consider earthly life, the only one we know, to be extremely valuable and protect it from "harmful contamination", whether it is terrestrial or extraterrestrial life acts. But that is a strange thought based on the fact that good is as it is, which ultimately leads from nature conservation to protection of homeland and culture, to the building of the wall and the defense against strangers. Likewise, it is absurd to try that terrestrial spacecraft should not contaminate another planetary biosphere. At most, this can be a scientific requirement in order to examine autochthonous life and preserve an "original".

If evolutionary, i.e. changing, mixing and adapting life is migratory and should or could be brought by meteorites to earth and from there to other planets under favorable growth conditions, then immigration is not harmful, but at most conditions that Damage life whatever it is. Living beings on a different biochemical basis could coexist with earthly life if they need other resources, otherwise evolution takes care of creative developments. The discussion about aliens, i.e. alien and invasive species, is directly interwoven with political ideas about what is our own and what is foreign. (Florian Rötzer)

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