USA: hypothetical chemical evolution on Titan may repeat the pre-stages of the origin of life

One of the most promising objects for the search for extraterrestrial life within the Solar System remains Saturn's moon Titan. The unique chemical and physical environment observed on this celestial body has once again become the focus of attention of astrobiologists. According to a recent theoretical study, the methane lakes of Titan can form stable organic structures, precursors of living cells-vesicles.

Titan has a dense methane-rich atmosphere in which complex photochemical reactions occur. Under the influence of solar radiation, an organic suspension is formed at an altitude, which settles to the surface in the form of so-called organic snow. This dust accumulates in the form of snowdrifts and, according to scientists, contains a wide range of carbon-containing compounds-from the simplest, like benzene, to more complex molecules, including potentially amphiphilic substances.

Methane on Titan is in all three aggregate states-gas, liquid, and ice-at temperatures around minus 180 degrees Celsius. It forms rivers, lakes, and even precipitation, making Titan the only celestial body other than Earth with a stable liquid on its surface. Under the thickness of the ice crust, according to the Cassini probe, there may be a global subglacial ocean capable of supporting liquid water.

The authors of the theory, which is being considered by the scientific community, suggest that structures resembling cell membranes can form in Titan's methane lakes. We are talking about vesicles — closed cavities surrounded by a double layer of molecules similar to lipids, but adapted to extremely low temperatures and liquid methane. The emergence of vesicles is one of the most important stages in models of the origin of life on Earth. They provide isolation of chemical processes from the external environment, which is critical for the formation of autonomous, stable molecular systems.

The process proposed by the scientists begins with the accumulation of amphiphilic molecules on the surface of lakes. When methane rain or hail falls, microscopic droplets are formed, covered with a layer of these substances. After re-falling into the lake, the interaction of layers leads to self-assembly of vesicles. Such formations are theoretically able to compete with each other for the surrounding resources — amphiphilic molecules — which can be considered as the primary form of natural selection and chemical evolution.

The presence of various vesicles with different physical and chemical properties creates conditions for the accumulation of stable combinations. In the long run, this can lead to the formation of more complex structures — protocells. These assumptions, despite their hypothetical nature, represent a consistent, experimentally reproducible model.

The researchers note that each stage of the proposed scheme can be verified in the laboratory. In addition, they suggest using a compact spectrometric instrument to search for and analyze vesicles directly on Titan. Similar equipment can be placed on board the Dragonfly mission, which is scheduled to launch in 2028. This rotary probe, which is being developed for flights in the satellite's atmosphere, is capable of delivering scientific instruments to various geochemical locations and obtaining direct data on the processes occurring on Titan.

It is not yet proven that Titan is capable of supporting life in the usual sense for us. However, the fact of a stable cycle of organic compounds in a liquid medium, the presence of amphiphilic molecules and potential conditions for self-assembly of membranes make this satellite an object of primary interest for astrobiology. With a growing focus on the exploration of extraterrestrial life, the Dragonfly project and subsequent missions could dramatically expand our understanding of the possibilities of chemical evolution beyond Earth.