Life Detection in the Solar System Using Molecular Assembly Theory
Cole Mathis
Arizona State University

The search for evidence of life elsewhere in the universe is hard because it is not obvious what signatures are unique to life. We postulate that complex molecules found in high abundance are universal biosignatures as they cannot form by chance. To explore this, we developed the first intrinsic measure of molecular complexity that can be experimentally measured based upon a new approach called assembly theory, which gives the molecular assembly number (MA) of a given molecule. MA allows us to compare the intrinsic complexity of molecules using the minimum number of steps required to construct the molecular graph starting from basic objects, and a probabilistic model shows how the probability of any given molecule forming randomly drops dramatically as its MA increases. To map chemical space, we calculated the MA of ca. 2.5 million compounds, and collected data which showed the complexity of a molecule can be experimentally determined by using fragmentation in a mass spectrometer. We then set out to see if this approach could allow us to identify molecular biosignatures with a set of diverse samples from around the world, outer space, and the laboratory including prebiotic soups. The results show that the higher the MA for a given molecule, the more likely that it is produced by a biological process. This work demonstrates it is possible to use assembly theory as the foundation for life detection instruments that could be deployed on missions to planetary surfaces to detect biosignatures.

Date:	Thursday, 16 November 2023
Time:	11:30
Where:	Université de Montréal
	Pavillon MIL A-3561