Solid-State Single-Molecule Sensing with the Electronic Life-detection Instrument for Enceladus/Europa (ELIE)

Abstract

Growing evidence of the potential habitability of Ocean Worlds across our Solar System is motivating the advancement of technologies capable of detecting life as we know it — sharing a common ancestry or common physicochemical origin to life on Earth — or don't know it, representing a distinct genesis event of life quite different than our one known example. Here, we propose the Electronic Life-detection Instrument for Enceladus/Europa (ELIE), a solid-state single-molecule instrument payload that aims to search for life based on the detection of amino acids and informational polymers (IPs) at the parts per billion to trillion level. As a first proof-of-principle in a laboratory environment, we demonstrate single-molecule detection of the amino acid L-proline at a 10 µM concentration in a compact system. Based on ELIE's solid-state quantum electronic tunneling sensing mechanism, we further propose the quantum property of the HOMO–LUMO gap (energy difference between a molecule's highest energy occupied molecular orbital and lowest energy unoccupied molecular orbital) as a novel approach to measure amino acid complexity. Finally, we assess the potential of ELIE to discriminate between abiotically and biotically derived α-amino acids in order to reduce false positive risk for life detection. Nanogap technology can also be applied to the detection of nucleobases and short sequences of IPs such as, but not limited to, RNA and DNA. Future missions may utilize ELIE to target preserved biosignatures on the surface of Mars, extant life in its deep subsurface, or life or its biosignatures in the plume, surface, or subsurface of ice moons such as Enceladus or Europa.

Nanogap Solid-State Single-Molecule Detection at Mars, Europa, and Microgravity Conditions

“…Figure 6a provides a comprehensive overview of event statistics, including the number of events, average tunneling current, and average dwell time per parabolic flight phase. This table extends our analysis by incorporating data from the parabolic flight into the context of prior ground experiments involving L-proline detection using the AXN system and the first-generation ELIE prototype [21, 24]. The distribution of average conductance versus average dwell time for each parabolic flight phase, along with the results from the aforementioned ground experiments, is visually presented in Figure 6b.…”

“…L-proline Event Level Analysis across Flight Phases and Ground. (a) Table summary of single-molecule average tunneling current and dwell time for L-proline across the different flight phases experienced by ELIE during the parabolic flight, and ground experiments performed by the next-generation ELIE prototype, the first-generation ELIE prototype [24], and the AXN system [21]. (b) Plot of single-molecule mean conductance and mean dwell time of L-proline events obtained during the parabolic flight phases and the ground experiments.…”

“…ELIE is designed to primarily target molecular biosignatures (e.g., amino acids and informational polymers) in future insitu life detection missions. The first low-technology readiness level (TRL) ELIE prototype proved the detection of the amino acid L-proline and demonstrated an extrapolated sensitivity of 1 nM [24]. However, this prototype required manual adjustments to maintain the nanogap, which could only be sustained for short intervals.…”