Production of complex prebiotic chemistry at Titan and Enceladus

One of the surprising discoveries with the Cassini-Huygens mission was of high mass per charge negative ions, indicative of prebiotic chemistry near Titan (Coates et al., 2007, 2009, 2010a, Wellbrock et al., 2013, 2019, Desai et al 2017a, Mihailescu et al., 2020), complemented by high mass positive ions (Haythornthwaite et al., 2021). Water clusters and other negative ions were also found in the Enceladus plume (Coates et al., 2010b), at Rhea (Teolis et al., 2010, Desai et al., 2017b), at Dione (Tokar et al., 2012, Nordheim et al., 2020), and in Saturn's magnetosphere. Similarly, charged dust was also found in the Enceladus plume with ELS (Jones et al., 2009, Hill et al 2012). These unanticipated measurements were made with the CAPS Electron Spectrometer (ELS), designed for electrons. The measurement technique used the spacecraft flyby velocity (~km/s) to separate the masses of cold ionospheric ions measured in the spacecraft ram direction. We recently studied the resolution available via this technique (Nicolaou, Haythornthwaite & Coates, 2022).

In addition, negative ions have also been detected at comets (Chaizy et al., 1991, Cordiner et al 2013, Burch et al. 2015), and at Mars, and may be present in the Venus environment also.

The capability to analyze and detect negative ions and charged dust with an instrument optimized for the task will be relevant for future missions, including potential Outer Planet Moons missions related to ESA Voyage 2050, and the Uranus Orbiter and Probe & Enceladus Orbilander missions identified in Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (NASA, 2022).

Water plays a key role in outer planet magnetospheres due to the presence of icy moons and rings, and icy plumes at Enceladus, Europa and Triton. O- as well as O+ ions are likely as at Saturn, and potentially Cl- as inferred at Europa from the subsurface ocean (Volwerk et al., 2001, Desai et al. 2017b).

In this project we will (1) Further analyse Cassini data on negative ions, (2) Work on the design and calibration of a new instrument concept to measure plasma, negative ions and charged dust in outer solar system environments, (3) Perform simulations to test the designs, (4) Perform laboratory tests of prototype instruments