Do extraterrestrials have a sense of humor?


Pointy ears, green blood and a rather dry sense of humor: like Spock from the science fiction series “Star Trek”, millions of people imagine aliens. Not only science fiction authors, but also researchers at universities around the world are concerned with the possibility of extraterrestrial life. Even if on a much smaller scale: “When we talk about life outside the earth, we are practically always referring to single-cell organisms. The mere discovery of permanent microbial stages outside the earth and its atmosphere would be surprising, ”explains Prof. Birgit Sattler. The biologist studies microorganisms on earth, especially those that live under extreme conditions: for example in the ice of the Antarctic or in high mountain lakes. Together with the chemist Prof. Bernd Rode and the astrophysicist Prof. Walter Saurer, she offers a seminar on astrobiology every summer semester - an interdisciplinary field of research that deals with the possibility of extraterrestrial life.

Life in space

A chemist, a biologist and an astrophysicist: the composition of the organizational team for the seminar alone shows the interdisciplinary relevance of astrobiology. “All life is first of all - also and especially - chemistry. Inorganic substances produce organic substances and ultimately building blocks of life; this is a process that we can even reproduce for the primordial earth in the laboratory, even if the exact mechanism of how the further development up to the first viable cell took place has not yet been researched, ”explains Bernd Rode. Chemistry can explain the basis on which extraterrestrial life can arise; and Bernd Rode rejects the possibility that an element other than carbon could be the basis of life: “There has been a lot of discussion, for example, that life could be based on silicon. After all the properties that we know of silicon, this can be ruled out. Theoretically, this would only be conceivable under completely different pressure and temperature conditions, but even then it is unlikely. "

How likely is life outside of the earth in principle? The astrophysicist Walter Saurer is confident: “From a purely statistical point of view, it is almost impossible that life only arose on earth. So far, we have discovered almost 2,000 planets outside of our solar system, almost 10 of which are similar to the earth - but extrapolated there are around 10 billion planets in our galaxy alone. ”Those in the so-called habitable zone - that is, the area of ​​a solar system in which the current one Knowledge that life can arise - are relatively difficult to discover, which is why astrophysicists assume that there are many more such planets.

Fermi paradox

The Italian physicist Enrico Fermi described the dilemma of the search for life as early as 1950 with a paradox: With the known age of the universe and the multitude of planets, more highly developed forms of life would have had far more than enough time to develop technologically to the extent that to seek contact with other living beings in space. “Fermi formulated the big question relatively early on: According to all the data available to us, there must be highly developed extraterrestrials. But: where are they? ”Explains Walter Saurer.

In addition to the search for planets outside our solar system (exoplanets), the researchers also concentrate on our own solar system - in addition to Mars, in particular on individual moons of Jupiter and Saturn. “In the laboratory we have already simulated the atmosphere of Titan, a moon of Saturn. A whole series of chemical compounds were formed there, solely through the very frequent lightning in the local atmosphere. This makes us confident that at least precursors of biomolecules could have developed there, which would enable further chemical evolution at higher temperatures, ”says Bernd Rode. There are also a number of inhospitable regions on earth in which there is still life: “The earth offers an incredibly diverse range of habitats, including those in which one would not expect any life at first. There are also single-cell organisms on earth that live under conditions similar to those found on Jupiter's moon Europe, for example, ”explains Birgit Sattler. There is water on Europe: the entire planet is surrounded by a thick layer of ice, with an ocean of water underneath. The moon is not only in the center of interest for the European Space Agency (ESA) because of this water resource: it is planning to start a probe mission to Jupiter in 2022, with which Europe will also be examined more closely.

Life on Venus?

But not only the moons of the outer planets, Venus was already being discussed for possible life: “For Venus, where temperatures exceed 400 degrees Celsius, there were similar theories that there could be life in the atmosphere just as atmospheric bioparticles are viable on Earth. But that is very unlikely, ”says Birgit Sattler. The conditions that prevailed in our solar system when life on earth came into being and that still prevail are, according to more recent findings, not as common as expected: “Our solar system has been considered typical up to now: huge gas planets outside, rocky planets like the earth closer in the sun and thus in the habitable zone. According to recent discoveries, solar systems look like ours is not so often the case, ”says Walter Saurer. On the contrary, more and more gas planets are being discovered that are very close to their suns - and that also have a very irregular orbit. "With the regular orbit around the sun and the ideal structure of the planetary system, our solar system is something special, an ideal incubator," explains the astrophysicist. However, large planets in the vicinity of the sun are also easier to discover than smaller, Earth-like ones. In any case, the search for life in space continues - also with the collaboration of researchers at the University of Innsbruck, who have already made important contributions to the still young astrobiology.

This article was published in the June issue of the magazine “wissenswert”. A digital version can be found here (PDF).