MICA: Microfluidic Icy-World Chemistry Analyzer

Abstract:

The Microfluidic Icy-World Chemistry Analyzer (MICA) is a sample-processor-integrated, microfluidic implementation of the Wet Chemistry Laboratory (WCL), an array of electrochemical sensors, including ion-selective electrodes (ISEs) and redox-active species measurement, that delivered key science findings on the Phoenix Mars mission. MICA’s science target, the surface chemical environments of the outer-planet icy moons Europa and Enceladus, are poorly understood—particularly with regard to habitability—yet their copious oceans make them promising locations to search in situfor extant life. By quantifying a wide range of ionic aqueous species, combinations of which are likely necessary for microbial habitation, MICA can dramatically increase our understanding of icy worlds and, with caveats for aging and radiation processing, of the oceans below. MICA’s electrochemical sensor array can map the chemical energetics of surfaces or plumes: measurement targets from dissolved gases (H₂, H₂S, CO, SO₂, O₂, NO₂) to metal ions spanning the periodic table have measurable electron-transfer properties that reveal the energetic differences necessary for life. MICA is being developed primarily to provide soluble-chemistry context, habitability information, and comparative oceanography data as an element of a payload instrument suite on search-for-life missions, e.g. for the proposed Europa Lander. MICA’s microfluidic system supports sample volumes from a few µL to many mL. It carries ultrahigh purity water and freeze-dried conditioning reagents and standards to prepare and calibrate sensors, which are configured as a pair of redundant, fluidically isolated sets of 24 sensors each, including multiple references. Replicate measurements will be made on multiple aliquots of each sample; samples are readily diluted by the microfluidic system so that high-concentration ionic species can be measured beyond the typical ~5-log dynamic range (~ 5 µM – 1 M) of most of the ISEs. MICA’s heritage includes the WCL instrument; six cubesat microfluidic/bioanalytical payloads proven in low-Earth orbit, a 6U nanosatellite biopayload for long-duration deep-space flight, the microfluidic WCL and Sample Processor for Life on Icy worlds (SPLIce) COLDTech projects, and an ICEE-2 project.