Nikola Kügler, April 2025
The central question of astrobiology is the question of extraterrestrial life, i.e. life outside the Earth. The aim is to clarify the origins, development and future of all forms of life in the universe. Exoplanets are of particular interest here. Even if the development of the Earth appears to be unique so far, one should ask oneself why there should not be a planet somewhere on which at least primitive life forms have developed, given the size of the universe. This is the subject of the relatively new field of astrobiology.
The search for life on astronomical objects is based on more detailed studies of terrestrial life, in particular research into so-called extremophiles. Extremophiles are organisms, usually archaea or bacteria, that can live under extreme environmental conditions. For example, thermophiles can withstand very high temperatures and radiophiles can tolerate high doses of radiation. A better understanding of their way of life allows conclusions to be drawn about the limits of life on earth and therefore also the limits of life in space.
Astrobiology also deals with the history of the earth. The focus here is on the question of the origin of life and the resulting enormous biological diversity that we know today. What factors play a role in creating a life-friendly planet and how can the environmental conditions remain constant over a sufficient period of time? The interactions between the planet’s environmental factors and the organisms are also relevant here.
The actual search for extraterrestrial organisms takes place in the form of the search for biomarkers, among other things. Measurement data from Earth or space can be used to detect the presence of certain molecules, for example water, and thus find explanations for earlier or even still-present life forms. In addition to atmospheric biomarkers, geological traces also play a role, as can be seen in the many missions to other celestial bodies in our solar system, e.g. the planets Venus and Mars or the icy moons Europa and Enceladus.
Jupiter’s moon Europa, photographed from a distance of 2745 km by the Juno space probe on September 29, 2022 Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
However, extrasolar planets, i.e. planets orbiting stars other than our sun, could be even more significant. The variety of discovered exoplanets with very different properties offers an enormous field for studying the formation and development of planetary systems. The most striking characteristics include size, mass, composition of the atmosphere, age and type of star. Of particular interest are those exoplanets that are located in the respective habitable or life-friendly zone of their star. However, this characteristic is by no means sufficient to be certain that life has actually developed on this planet.
Astrobiology is a rapidly expanding field of research. There are many questions on the way to the discovery of extraterrestrial life, so there are many interesting fields of work. The discovery of life in space could change our fundamental understanding of our place in the universe and is therefore also of philosophical relevance.