Scientists have discovered that under the extreme conditions on Saturn's moon, unique structures can form that combine substances normally considered incompatible.

Titan is the only object in the Solar System, aside from Earth, that has surface lakes. However, these lakes are not filled with water, but with liquid methane, which circulates in a dense atmosphere at temperatures around minus 180°C. In Titan's northern hemisphere, methane clouds and hydrocarbon rains are regularly observed.

Researchers are particularly interested in hydrogen cyanide (HCN)—a polar molecule formed in Titan's upper atmosphere from nitrogen, methane, and ethane. This compound triggers a chain of chemical reactions that lead to the synthesis of amino acids and other components essential for primitive life forms.

An international team of scientists conducted an experiment simulating Titan's conditions: they condensed methane and ethane vapors onto hydrogen cyanide crystals at minus 180°C. The results, published in the journal PNAS, were unexpected.

It turned out that polar hydrogen cyanide can mix with nonpolar methane and ethane, forming stable co-crystals and solid solutions. This contradicts the fundamental chemical principle of "like dissolves like," which states that substances with different polarity should not mix.

Spectroscopy revealed a strengthening of hydrogen bonds after hydrocarbon molecules were incorporated into the crystal structure. Computer modeling confirmed these findings. The most stable structures were those containing 10–20% ethane.

The energy difference between the pure substances and the new structures was only 0.5–1 kJ/mol, allowing co-crystals to form spontaneously under Titan's conditions.

These crystals could play a key role in the moon's geology: they are capable of trapping methane and ethane in solid form, creating unique hydrocarbon reservoirs. When temperature and pressure change, the co-crystals release their contents, which may lead to erosion and changes in the landscape. This process could explain the appearance of temporary "methane islands" on Titan's lake surfaces.

Definitive confirmation of the existence of these co-crystals is expected during NASA's Dragonfly mission, which is scheduled to reach Titan in 2034.