Quantifying Global Origin-Diagnostic Features and Patterns in Biotic and Abiotic Acyclic Lipids for Life Detection

Area of Science:

• Astrobiology
• Organic Geochemistry
• Planetary Science

Background:

• Lipids are essential organic molecules found in all known life.
• Lipid-like organic compounds have been detected in meteorites and on Mars, raising questions about their origin.
• Distinguishing between biotic (life-produced) and abiotic (non-life-produced) lipids is crucial for astrobiology.

Purpose of the Study:

• To identify origin-diagnostic molecular features and patterns in fatty acids and acyclic hydrocarbons.
• To develop methods for distinguishing between biogenic and abiogenic lipid synthesis.
• To inform the search for life on Mars by analyzing extraterrestrial organic molecules.

Main Methods:

• Analysis of molecular data from over 1500 published studies of terrestrial and meteoritic organic samples.
• Identification of 27 molecular patterns and structural features for distinguishing lipid origins.
• Application of Principal Component Analysis (PCA) to multivariate molecular data for origin indication.

Main Results:

• 15 patterns for fatty acids and 12 for acyclic hydrocarbons were identified as origin-diagnostic.
• Terrestrial lipids are characterized by longer, straight-chain molecules with specific branched/unsaturated isomers.
• Meteoritic lipids are generally shorter with random configurations, differing from terrestrial lipids.

Conclusions:

• Multivariate analysis of molecular features can potentially indicate the origin of lipids.
• The identified features provide a framework for assessing the biogenicity of extraterrestrial lipids.
• A novel instrument, ExCALiBR, was designed to extract lipids while preserving origin-diagnostic features for biogenicity assessment.