Scientists have proposed to revise the list of criteria that the planet needs in order for life to appear on it. They believe that this can happen not only on those planets whose crust consists of lithospheric plates moving relative to each other, and this condition is no longer necessary. The results of the work are presented in the journal Astrobiology.
In recent years, astronomers have discovered over a thousand exoplanets, and recently launched TESS satellite should open tens of times more. Scientists do not doubt that the conditions on most of them are too harsh for life to appear there. However, it was rather difficult to determine which of the conditions are obligatory for life, and which ones are not very. For example, scientists believe that for the habitation of the planet on it should be a fairly dense atmosphere, which can keep the temperature on the surface of the celestial body in a limited range, including through greenhouse gases. An example of such a gas is CO2.
“Volcanoes throw different gases into the atmosphere. Gradually, carbon dioxide leaves it and remains in the form of sediments on the surface [of the planet], “says co-author Bradford Foley of the University of Pennsylvania (USA). “The balance between these two processes maintains a certain level of carbon dioxide in the atmosphere, which is important for [the planet] to maintain a stable climate and a suitable temperature for life.”
In the new work, the authors decided, using computer simulations, to compare how much heat is released from the depths of planets of two types – with active tectonic processes and with one solid plate that floats on the surface of the molten mantle. The program with simulation was launched hundreds of times – for virtual planets of various sizes and composition. As a result, it turned out that celestial bodies, the surface of which does not consist of moving lithospheric plates, can also maintain conditions for habitation – that is, liquid water can be on their surface for billions of years.
Volcanism on such planets should be, although it is much less active than on planets of the first type. However, due to the fact that lava under a single lithospheric plate is mixed badly, volcanoes will constantly erupt in the same places. This will lead to the accumulation of rocks rich in gases on the surface of the planet.
Nevertheless, the authors come to the conclusion that at sufficient temperature and pressure, carbon dioxide can still be released and enter the atmosphere. However, the intensity of this process depends heavily on the type and amount of radioactive elements on the planet. The fact is that during the decay they further warm up the planet. As a result, the authors consider the presence and concentration of elements heating the subsoil as an important criterion for the emergence of life.