The celestial body Titan presents a compelling stimulus for the in-depth investigation of organic chemistry operating under unusual environmental parameters. This moon of Saturn hosts abundant nonpolar hydrocarbons, including methane and ethane, in addition to hydrogen cyanide (HCN), a small molecule of significant prebiotic importance and pronounced polarity. Recent scientific inquiry has furnished evidence suggesting the intermingling of these starkly contrasting polar substances at cryogenic temperatures, resulting in the formation of configurations that challenge conventional chemical paradigms.
An artistic rendering of Kraken Mare, a large liquid methane sea on Titan. Image credit: NASA’s John Glenn Research Center.
Hydrogen cyanide is ubiquitously present across astrochemical domains, having been detected within the interstellar medium and across a variety of astronomical entities such as comets, planets, moons, and dwarf planets.
This particular molecule is anticipated to be the second-most prevalent output from the atmospheric chemical processes occurring on Titan.
“These represent exceptionally noteworthy discoveries that can substantially enhance our comprehension of broader phenomena, specifically concerning a moon comparable in size to the planet Mercury,” stated Dr. Martin Rahm, a research scientist affiliated with Chalmers University of Technology.
Within their laboratory endeavors, Dr. Rahm and his associates combined hydrogen cyanide with methane and ethane, subjecting them to temperatures as low as 90 K (equivalent to approximately minus 180 degrees Celsius).
Under these frigid conditions, hydrogen cyanide assumes a crystalline state, while methane and ethane remain in their liquid phases.
Subsequent examination of these mixtures by the researchers, employing laser spectroscopy – a technique utilized for the atomic-level analysis of materials and molecules – revealed that while the molecules themselves remained intact, a notable transformation had nonetheless occurred.
To elucidate this phenomenon, extensive computational simulations were undertaken to explore numerous potential arrangements of the molecules within the solid matrix.
The simulations indicated that hydrocarbon molecules had permeated the crystalline structure of hydrogen cyanide, thereby generating novel and stable formations identified as co-crystals.
“The revelation of this unanticipated interaction between these chemical species has the potential to reshape our understanding of Titan’s geological makeup and its distinctive physiographic features, such as its extensive lakes, seas, and dune formations,” commented Dr. Rahm.
“Furthermore, hydrogen cyanide is likely to play a pivotal role in the abiotic genesis of fundamental biological constituents, including amino acids, which are instrumental in protein synthesis, and nucleobases, essential components of the genetic code.”
“Consequently, our research also contributes valuable insights into pre-life chemistry and its potential progression within extreme and uncongenial environments.”
The findings were disseminated in July 2025 through the esteemed journal, Proceedings of the National Academy of Sciences.
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Fernando Izquierdo-Ruiz et al. 2025. Hydrogen cyanide and hydrocarbons mix on Titan. PNAS 122 (30): e2507522122; doi: 10.1073/pnas.2507522122
