The presence of organic molecules that have arisen from biological processes is a crucial indicator of life. Hydrocarbons are the most prevalent organic compound in all living things.
They do not have to be created through the heat breakdown of microorganisms or sedimentary organic materials, though. Therefore, even though hydrocarbons have been discovered in a number of locations outside of Earth, they are not always a sign of extraterrestrial life. These hydrocarbons might have developed as the result of abiotic processes.
Therefore, the key to determining whether a hydrocarbon is of biotic or abiotic origin is determining its origin. Unfortunately, so far, this endeavor has proven to be incredibly difficult.
Luckily, a team of researchers led by Professor Yuichiro Ueno from Tokyo Institute of Technology (Tokyo Tech) has now risen to the occasion. By examining the relative abundance of an isotope of carbon, specifically 13C-13C, in organic molecules, the team reveals an innovative and reliable method for differentiating the sources of hydrocarbons.
Talking about their research, published in Nature Communications, Professor Ueno comments, “While methods to distinguish the source of the hydrocarbon, such as compound-specific isotope analysis, are available, they require a whole set of molecules, all of which are not always available to sample. In contrast, our method allows us to use the information contained in the molecule to find the source of its origin.”
This new approach can help us identify the origin of organic molecules, both on earth and in extraterrestrial environments. It can easily differentiate between thermogenic, abiotic, and microbially produced hydrocarbons. While more interlaboratory work needs to be done for further calibration of the method, we believe it can potentially help detect the signatures of life elsewhere the universe.
Professor Yuichiro Ueno
The researchers examined the relative abundance of several carbon isotopes in ethane in order to make use of this knowledge. The number of ethane molecules with two 12C atoms, one 12C and one 13C atom, and both 13C atoms were compared.
The scientists used this information to determine the amount of 13C-13C in the sample’s ethane molecules. They compared the value of the 13C-13C abundance in natural gas ethane to that produced in a lab.
They found that 13C-13C abundance in natural gas ethane, which is produced via thermal decomposition of organic matter, was relatively higher than what one would expect based on the natural abundance of 13C.
The team asserts that this results from carbon bonding in the organic molecules that generate natural gas. The ethane synthesized abiotically, however, displayed a relatively reduced abundance of 13C-13C. Additionally, they observed that microbially-produced ethane had even higher 13C-13C abundance than thermogenic ethane.
“This new approach can help us identify the origin of organic molecules, both on earth and in extraterrestrial environments. It can easily differentiate between thermogenic, abiotic, and microbially produced hydrocarbons,” highlights Professor Ueno. “While more interlaboratory work needs to be done for further calibration of the method, we believe it can potentially help detect the signatures of life elsewhere the universe.”
