Workshop on the Habitability of Icy Worlds (2014) 4034.pdf

Returning Samples from Icy Enceladus Peter Tsou1, Ariel Anbar2, Donald E. Brownlee3, John Baross3, Daniel P. Glavin4, Christopher Glein5, Isik Kanik6, Christopher P. McKay7, Hajime Yano8, Peter Williams2 and Kathrin Atwegg9 1Sample Exploration Systems, 2Arizona State University, 3University of Washington, 4NASA Goddard Space Flight Center, 5Carnegie Institution of Washington, 6Jet Propulsion Laboratory California Institute of Technology, 7Ames Research Center, 8Japan Aerospace of Exploration Agency, Institute of Space and Astronautical Science, 9 University of Bern. Email: [email protected].

Introduction: From the first half century of space acids, determining the sequences of any oligomers, exploration, we have returned samples only from the assessing chirality and chemical disequilibrium, and Moon, comet Wild 2, the Solar Wind and the asteroid measuring isotope ratios, we can formulate a new set Itokawa. The in-depth analyses of these samples in of hypotheses to address many of the key science ques- terrestrial laboratories have yielded detailed chemical tions required for investigating the stage of extraterres- information that could not have been obtained without trial life at Enceladus beyond the initial four factors of the returned samples. While obtaining samples from habitability. At a broader level, Enceladus is offering Solar System bodies is transformative science, it is us a unique opportunity to search for new insights into rarely done due to cost and complexity. The discovery the puzzling transition between the ubiquitous prebio- by Cassini of geysers on Enceladus and organic mate- tic chemistry of asteroids and comets, and the bioche- rials in the ejected plumes indicates that there is an mistry at the root of all known life. There is also much exceptional opportunity and strong scientific rationale to be learned about the geochemistry of oceans inside to do a low-cost flyby sample return mission. The icy worlds as a general phenomenon by studying Ence- earliest low-cost possible flight opportunity is the next ladus as a test case. Discovery Mission [Tsou et al 2012]. Criticality of Laboratory Analyses: - For extra- Enceladus Plume Discovery: While Voyager pro- terrestrial organic compound analyses such as chirality vided evidence for geologically young regions on and compound-specific isotope ratio determination, the Enceladus, Enceladus' plumes, active tectonics, and repeatable robustness of laboratory measurements is high heat flux were discovered by Cassini. Enceladus essential. In general, these analyses require a variety also appears to be the only known Solar System body of chemical extraction and derivatization steps prior to outside of Earth where samples of recently frozen liq- analysis that are adapted to the sample and procedures uid water can be accessed from space, as the jets con- that can be modified according to the results obtained. veniently enable sample collection in a flyby without The Stardust mission is an excellent example of the landing or surface contact, similar to Stardust and challenges in the analysis of organics. Confirmation of Hayabusa. the cometary origin of the amino acid glycine from Cassini in situ Findings: Cassini has made many comet Wild 2 was obtained 3 years after the samples key discoveries at the Saturn system, including the were returned to Earth. This long period of laboratory fragmentation of relatively heavy organics from the testing and development allowed several modifications plumes of Enceladus. Four prime criteria for habitabi- to the extraction protocol, involving multiple analytical lity are liquid water, an energy source, organics and techniques and instrumentation. nitrogen [McKay et al. 2008, Waite et al. 2009, Post- berg et al. 2011]. Out of all the NASA designated ha- In Situ Measurement: Cassini results have sug- bitability targets, Enceladus is the single body that gested the existence of larger organic molecules with presents the clearest evidence for all four criteria. Si- intriguing astrobiological possibilities in both the gnificant advancement in assessing the biological po- Enceladus jets. The proposed LIFE payload would tential of Enceladus can be made on returned samples include a mass spectrometer with significantly greater in terrestrial laboratories where the full power of state- mass resolution than the 99 amu resolution of Cassini of-the-art laboratory instrumentation and procedures instruments. We would also carry a camera and a dust can be used. Without serious limits on power, mass or counter to capture ephemeral aspects of the plume not even cost, terrestrial laboratories provide the ultimate captured in the samples. In situ measurements provide in analytical capability, adaptability, reproducibility essential context to the returned samples. and reliability. What Questions can Samples Address? Samples col- References: Tsou et al., Astrobiology 2012. lected from the Enceladus plume will enable a tho- McKay et al. Astrobiology 2008. Waite et al. Nature rough and replicable search for possible extraterrestrial V 460 I 7254, 2009. Postberg et al. EPSC 642P 2011. organisms and biosignatures [Glavin et al. 2011], Glavin et al., LPSC, #5002, 2011. which would propel our understanding of the habitabi- lity of the subsurface ocean of Enceladus. By searching for amino acids and peptides, nucleotides and nucleic