In a new study, scientists propose passing an electric current through a sample to determine which isomers of organic compounds it contains. This could help establish whether the carbon compounds found in it are the result of biological activity.
Organic Compounds in Space
Scientists have long been developing methods to find life beyond Earth. In theory, this does not even require observing extraterrestrial beings: examining material samples from other worlds and identifying biomarkers would be enough. In practice, however, there is a problem, and phys.org reports on a potential solution.
The study was conducted by researchers at Osaka University in Japan and published in Nature Communications. The researchers sought to determine how to distinguish organic compounds formed through nonbiological processes from those produced by the activity of extraterrestrial organisms.
The problem is not that carbon-based compounds are absent from space or that we cannot detect them. Thanks to meteorites, probes on other planets, and spectroscopy, we know that such substances are abundant beyond Earth. The difficulty lies elsewhere: almost everything detected so far does not necessarily have a biological origin, however complex its composition may be. This applies even to the components of DNA and proteins.
Identifying Isomers
However, scientists are well aware of one characteristic that clearly indicates that organic matter originates from living organisms—a departure from chiral purity. Many complex substances have several isomers: molecules containing the same number of atoms of each element but having different structures. Particularly revealing are left-handed and right-handed isomers, which are like mirror images of one another.
In substances produced through abiotic processes, left-handed and right-handed isomers occur in equal proportions. However, living organisms, at least on Earth, consist exclusively of left-handed amino acids and right-handed proteins. The same ratio is therefore observed in biomarkers.
The only problem is how to measure this ratio in samples. Methods already exist, but they rely on chemical reactions that do not provide sufficient accuracy and often destroy proteins. In the new study, the authors instead propose determining this ratio by passing an electric current through a sample.
In their laboratory setup, they placed material samples between two gold plates and observed how electrical breakdown occurred after charge accumulated between them. They claim that this approach can determine the chirality of even individual atoms within a given sample. Moreover, the setup is simple enough to be used on Mars rovers, for example.
