P001-05
Hypervelocity Sampling of the Enceladus Plume: Implications for Astrobiology Investigations
Monday, 7 December 2020: 04:29
Virtual
Sarah E. Waller1, Andres Jaramillo-Botero2, Morgan E.C. Miller3, Sally Burke4, Robert Continetti3, Robert P Hodyss5, Michael Malaska6, Amy Hofmann1, Bernd Abel7, Frank Postberg8, Jonathan I Lunine9 and Morgan L Cable10, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)California Institute of Technology, Pasadena, CA, United States, (3)University of California San Diego, La Jolla, United States, (4)University of California San Diego, La Jolla, CA, United States, (5)Jet Propulsion Laboratory, Pasadena, CA, United States, (6)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (7)University of Leipzig, Leipzig, Germany, (8)Freie Universitӓt Berlin, Berlin, Germany, (9)Cornell University, Department of Astronomy, Ithaca, NY, United States, (10)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
Abstract:
Enceladus is one of the most likely places to find evidence of extant or extinct extraterrestrial life. Enceladus has a global, subsurface, liquid water ocean with evidence to support hydrothermal activity at the ocean-core interface. The plume of Enceladus, likely originating from the subsurface ocean, allows the ocean to be characterized without the need for a landed mission and contains a plethora of organic molecules. The CDA instrument utilized Cassini’s velocity to characterize molecules within plume ice grains via impact-induced ionization. However, impact-induced ionization under these conditions is not well understood, and it is unclear if this process can be “soft” enough to keep large organic molecules intact for subsequent mass spectral analysis. It is critical to understand these processes and how they affect organic molecule survivability for a return mission to Enceladus to search for signs of life and to characterize the subsurface ocean composition via the plume.
Combined experimental and theoretical efforts are underway to better understand the impact-induced ionization of molecules and ice grains at hypervelocity (>3 km/s) and to characterize the survivability of organic biosignatures within the plume. A first-principles based approach has been used to run simulations of amino and fatty acid fragmentation, indicating organics begin to fragment at 3-5 km/s when bare and at 4-6 km/s when entrained within an ice grain. Two lab-based instruments that experimentally reproduce ice grain impacts during a spacecraft flythrough encounter will be used to validate fragmentation thresholds. The Aerosol Impact Spectrometer (AIS) at UCSD is capable of accelerating and impacting a single, charged ice grain and measuring the mass spectra of impact-generated ions with velocities up to 5 km/s. The Hypervelocity Ice Grain System (HIGS) at JPL generates an ensemble of neutral and charged species traveling at 2-5 km/s and is being modified to measure post-impact mass spectra at various velocities. After modification, the HIGS apparatus will be capable of coupling to flight instruments for validation and generating mass spectral libraries to facilitate astrobiology-focused mission data interpretation. Results of initial impact-generated ion studies using the HIGS apparatus will be discussed.
