PlumeCAS: A Novel Plume Capture and Potential Biosignature Detection Instrument

PlumeCAS is an all-in-one sample capture, volatile metering, and Capillary Absorption Spectrometer (CAS) system that can make sensitive isotopic and abundance measurements of H2O, CO2, CH4, and C2H6 in Enceladus’ plume to aid in the search for life. The instrument accumulates gaseous and icy phases during plume flythroughs in an aerogel and indium collector that preserves the integrity of small organics. The flight system would leverage a heritage hermetic sealing design to contain that sample, and a volatile metering system delivers aliquots to the CAS for analysis. There, hydrogen and carbon isotopic ratios of H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O and CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> are measured to generate a baseline against which to compare isotopic ratios in CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>. PlumeCAS will also determine the abundances of CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> and C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> to generate a CH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>/C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> abundance ratio. These isotopic and abundance indicators are among the best-understood biosignatures available for measurement in Enceladus plume material. This analysis is nondestructive, and therefore the system has the potential to have additional gas analysis instruments added in series with the CAS. In this paper we describe the scientific motivation for the instrument, the breadboard hardware development and test campaign that validated this concept to TRL 4, and future work that may be done to better prepare the system for flight.