Researchers at Osaka University have devised a new method for finding signs of life on other planets that combines artificial intelligence with electrical signals. Their goal is to build a tool that is sensitive enough yet small enough to be sent to another planet.
Finding life in space requires searching for “biosignatures,” i.e., traces left by living organisms. The difficulty is that instruments must be both highly sensitive and compact so they can practically be sent to another planet.
One common way to distinguish living from nonliving processes is to examine amino acids; the building blocks of proteins. Amino acids, despite having the same chemical formula, exist in two mirror-image forms. In living organisms amino acids are almost all of the “L” form and sugars of the “D” form, while abiotic processes produce both forms in roughly equal amounts. Therefore the ratio between these two forms can be a biosignature. However, practical implementation so far has been impossible because it requires collecting large ensembles of molecules and the vast distances between planets make this difficult.
To solve this problem, the researchers turned to electric current. Such a method is simpler, less sensitive to vibration during sampling, and does not require chemical reagents.
In the new study, the scientists were able to count molecules as they passed through the gap between two very thin gold wires. The waveform of the current depends on the type of amino acid and the device can distinguish them by counting molecules as they pass.
Takahito Oshiro, the lead author of the paper, says that by combining nanogap tunneling and artificial intelligence they were able to distinguish the “L” and “D” forms of amino acids with an accuracy of over 80 percent. According to him, this is the first time amino acid chirality has been discriminated at the single-molecule level and this achievement is a fundamental advance in chemical sensing. (Chirality is a property in which an object is not superimposable on its mirror image; many important biological molecules, including amino acids and sugars, are chiral.)
To test the method, they applied it to two terrestrial samples: one from the Murchison meteorite in Australia and the other from soil in the Atacama Desert in Chile. The method’s performance was comparable to conventional methods and determined the amino acid composition of the samples.
The researchers hope to use this technology to build small electrical instruments that can identify extraterrestrial signs of life.
This research, titled “Discrimination of amino acid chirality in meteorite and desert soil extracts via single-molecule nanogap conductance,” was published in the journal Nature Communications.