Metals are not usually considered biomarkers. But in a recently published study, scientists recalled that they participate in redox reactions. And that is precisely why we should look for them if we want to find extraterrestrial life.
Chemistry of life
In a recent article published in The Open Journal of Astrophysics, researchers from the University of Naples suggested that the presence of traces of metals on an exoplanet could indicate the presence of living organisms on it. This statement is quite unexpected for the entire search for extraterrestrial life.
Fact is, life as we know it on Earth is a bunch of chemical reactions between hydrocarbons that happen in water and mostly involve oxygen. Accordingly, scientists are primarily looking for traces of these substances on other planets.
Sometimes it is also mentioned that there should be a specific source of energy, such as starlight or volcanic activity. However, even with this definition, life is still imprecise. It is the result of unbalanced chemical reactions.
And to be more specific, these are redox reactions. They usually undergo powerful electron transfer. An example of this is respiration, the emergence of which greatly changed the entire appearance of the Earth in the distant past.
Metals on exoplanets
And in order for redox reactions to occur, metals have to be involved as catalysts. Moreover, metals are not in the astronomical sense (i.e., not all chemical elements heavier than helium, but only those that are considered metals in chemistry).
For example, nickel and iron are key components of proteins that take electrons from hydrogen, while copper is a key component of proteins that interact with oxygen. Metals make up a very small proportion of the mass of living organisms, but they are extremely important as catalysts.
The authors of the study believe that it is still worth trying to take an interest in those planets that orbit metal-rich stars. At the same time, they understand that the probability of finding hydrocarbons is still higher.
According to phys.org
