Targeting Microhabitats in Ice For Life Detection

The search for life on other worlds is one of the most significant drivers of scientific exploration. On Earth, microbial life inhabits tiny places on a scale of hundreds of microns across or even smaller. These microhabitats and niches have favorable physical conditions and chemical disequilibria, enabling life to survive and thrive locally. For example, in the Greenland Ice Sheet, ultrasmall microbes live under cold, dark, high-pressure conditions found kilometers below the surface (Miteva and Brenchley 2005). In the deep ice, microbes survive in hypersaline liquid micro-pockets located between ice grains (Price 2000, Junge, Krembs et al. 2001, Junge, Eicken et al. 2004, Mader, Pettitt et al. 2006, Barletta, Pricsu et al. 2012). Since terrestrial deep ice microhabitats may have similar physical and chemical conditions as those deep locations in the icy crusts of the Ocean Worlds of the Solar System, such as Europa, Enceladus, and Titan Titan (Priscu and Hand 2012, Vance, Panning et al. 2018), it is possible that those alien microenvironments are inhabited and thus are excellent targets in the search for life. Unfortunately, current techniques for looking and sampling for life on other worlds operate at the bulk scale, on the order of 1 cm3 (1E–6 m3) or larger (Hand, Murray et al. 2016) Lander Study report. The current paradigm for identifying extraterrestrial biosignatures involves multiple approaches, including detecting distinctive chemical signatures, looking for likely morphologies, and measuring for metabolic activity. Compared to current strategies involving large-scale bulk sampling, targeting microenvironments will improve the signal-to-noise for each approach. This is because specifically targeting the microenvironments leads to the acquisition of less of the surrounding matrix (e.g., ice), which in turn means that the resulting chemical and biological signals are less diluted. The resulting increase in signal strength could be up to two orders of magnitude (Malaska, Bhartia et al. 2020). In a nutrient-starved environment, such as those predicted for the Ocean Worlds (Affholder, Guyot et al. 2022, Neish, Malaska et al. 2024), this signal increase could translate to the difference between detection and non-detection of key biosignatures. In addition, by specifically targeting the individual microenvironments, any detected signals can be placed within the local chemical context without comingling of surrounding matrix. By developing technologies to target, extract, and analyze the contents and context of potentially inhabited alien microenvironments, we will significantly advance our search for life in alien environments. Our KISS study identified techniques and technologies for instrumentation and robotics to be able to identify, target, sample, and analyze microenvironments in Ocean World environments and also the surface of ice-rich areas on Mars. Implementation of these requirements could enhance capabilities for future astrobiological exploration Mars and the Ocean Worlds during in situ surface or subsurface missions.