  The quest to find extraterrestrial life is a critical scientific endeavor
with civilization-level implications. Icy moons in our solar system are
promising targets for exploration because their liquid oceans make them
potential habitats for microscopic life. However, the lack of a precise
definition of life poses a fundamental challenge to formulating detection
strategies. To increase the chances of unambiguous detection, a suite of
complementary instruments must sample multiple independent biosignatures (e.g.,
composition, motility/behavior, and visible structure). Such an instrument
suite could generate 10,000x more raw data than is possible to transmit from
distant ocean worlds like Enceladus or Europa. To address this bandwidth
limitation, Onboard Science Instrument Autonomy (OSIA) is an emerging
discipline of flight systems capable of evaluating, summarizing, and
prioritizing observational instrument data to maximize science return. We
describe two OSIA implementations developed as part of the Ocean Worlds Life
Surveyor (OWLS) prototype instrument suite at the Jet Propulsion Laboratory.
The first identifies life-like motion in digital holographic microscopy videos,
and the second identifies cellular structure and composition via innate and
dye-induced fluorescence. Flight-like requirements and computational
constraints were used to lower barriers to infusion, similar to those available
on the Mars helicopter, "Ingenuity." We evaluated the OSIA's performance using
simulated and laboratory data and conducted a live field test at the
hypersaline Mono Lake planetary analog site. Our study demonstrates the
potential of OSIA for enabling biosignature detection and provides insights and
lessons learned for future mission concepts aimed at exploring the outer solar
system.
