Scientists from Chalmers University of Technology in Sweden and NASA have made a surprising discovery on Saturn’s largest moon, Titan, that challenges one of the most basic principles in chemistry.
The finding could change how researchers think about the chemistry that existed before life began on Earth—and possibly elsewhere in the universe.
Titan is an icy world shrouded in a thick, orange haze made mostly of nitrogen and methane.
It is one of the most Earth-like bodies in the solar system, with lakes, rivers, and seas of liquid methane and ethane on its surface.
Because Titan’s conditions may resemble those of early Earth billions of years ago, scientists have long studied it to understand how life’s building blocks might first have formed.
A research team led by Associate Professor Martin Rahm at Chalmers discovered that, in Titan’s extreme cold, certain types of molecules that normally don’t mix can actually combine to form new, stable structures.
The study, published in PNAS and conducted with NASA’s Jet Propulsion Laboratory (JPL), shows that hydrogen cyanide, a highly polar molecule, can form crystals together with nonpolar molecules such as methane and ethane.
On Earth, these substances behave like oil and water—staying completely separate. But on Titan, at around –180°C, they can blend in unexpected ways.
“This is a very exciting finding,” said Rahm. “It helps us understand Titan—a moon as large as Mercury—and also offers clues about the chemistry that existed before life began.”
Hydrogen cyanide is especially interesting to scientists because it can react to form amino acids and nucleobases, essential components of proteins and DNA.
Discovering that it can interact with methane and ethane suggests that Titan could host a unique type of chemistry, one that operates differently from anything seen on Earth.
The research began when scientists at NASA’s JPL wondered what happens to hydrogen cyanide after it forms in Titan’s atmosphere.
They conducted laboratory experiments, mixing hydrogen cyanide with methane and ethane at Titan-like temperatures.
Using laser spectroscopy, they found that the molecules did not react chemically—but something had changed in their structure. To solve the mystery, they turned to Rahm’s team in Sweden, which specializes in studying hydrogen cyanide.
Together, the teams used powerful computer simulations to model thousands of possible molecular arrangements. Their calculations revealed that hydrocarbons can slip into the crystal structure of hydrogen cyanide, forming what are known as co-crystals—stable, mixed solids that can exist under Titan’s freezing conditions. The simulations also predicted light patterns that matched NASA’s experimental results, confirming the discovery.
This finding challenges the long-accepted chemistry rule “like dissolves like,” which states that polar and nonpolar substances cannot mix. However, Rahm sees it not as an exception but as an expansion of what’s possible in chemistry. “It shows that even well-known rules have their limits under extreme conditions,” he said.
The timing of the discovery is perfect. NASA’s Dragonfly spacecraft, scheduled to launch in 2028 and arrive at Titan in 2034, will explore the moon’s surface and search for signs of prebiotic chemistry—the chemical steps that could lead to life. Rahm and his colleagues hope their work will help guide future studies. “Hydrogen cyanide is found throughout the universe,” he said.
“Our findings may help explain how life’s chemistry could begin in the coldest and most unexpected places.”
Source: KSR.
