Radar probing of Jovian icy moons: Understanding subsurface water and structure detectability in the JUICE and Europa missions

Five decades of radioglaciology

“…Two instruments have been selected for upcoming missions to Ganymede and Europa: the 9 MHz frequency Radar for Icy Moons Exploration (RIME) instrument on board the European Space Agency's Jupiter Icy Moons Explorer (JUICE) and the 9 and 60 MHz frequency Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) instrument on board NASA's Europa Clipper (Bruzzone and others, 2013; Pappalardo and others, 2015; Lorente and others, 2017; Blankenship and others, 2018). These sounders are designed to probe the moons' interiors and have penetration depths which are functions of surface roughness, volume scattering, ice-shell thermal structure, chemistry and the character of the ice/water interface (Moore, 2000; McKinnon, 2005; Blankenship and others, 2009; Bruzzone and others, 2011; Schmidt and others, 2011; Berquin and others, 2013; Grima and others, 2014b; Pettinelli and others, 2015; Di Paolo and others, 2016; Grima and others, 2016; Aglyamov and others, 2017; Heggy and others, 2017; Kalousová and others, 2017; Campbell and others, 2018; Gerekos and others, 2018; Michaelides and Schroeder, 2019; Culha and others, 2020). The addition of a dual-channel VHF band on REASON also allows for characterization of the European ionosphere, altimetric investigation of Europa's shell and tides, and dual-frequency or interferometric clutter discrimination (Grima and others, 2015; Carrer and Bruzzone, 2017; Castelletti and others, 2017; Haynes and others, 2018a; Steinbrügge and others, 2018; Scanlan and others, 2019).…”

Assessing the detectability of Europa’s eutectic zone using radar sounding

“…where ε l,f , ε l,s , and ε l,b are the permittivities of pure, saline and brine water, respectively (Neal, 1979;Peters et al, 2005;Pettinelli et al, 2016;Heggy et al, 2017) and i = √ −1.…”

“…These radar sounders have the potential to image subsurface features within the ice shell including the ice/ocean interface (Moore, 2000) and shallow water bodies (e.g., Schmidt et al, 2011). Additionally, water bodies in the eutectic zone of Europa's ice shell (Kalousová et al, 2017;Heggy et al, 2017) could serve as radar sounding targets. The eutectic zone is the portion of the ice shell with pressures and temperatures that allow both the liquid and solid phases of water to exist.…”

“…Di Paolo et al, 2017;Blankenship et al, 2009;Haynes et al, 2018) or ice shell propagation/attenuation model (e.g. Kalousová et al, 2017;Heggy et al, 2017).…”

Probing groundwater in arid environments: challenges and opportunities south of the Mediterranean basin

“…With the exception of Mars' icy polar-layered deposits, the ability of sounding radar to detect liquid water (e.g., Orosei et al 2018) in desiccated and rocky terrains has been compromised by the high electrical conductivity that constitutes Mars' volcanic upper crust (Heggy et al 2006). Additional shallow subsurface radar investigations include two ground penetrating radar experiments for Mars aboard NASA's Mars 2020 rover and ESA's ExoMars rover (Ciarletti et al 2017); SELENE radar for the Moon (Ono et al 2008); CONSERT radar for comet 67P (Kofman et al 2015); and two sounding radars aboard the JUICE (ESA) and Europa Clipper (NASA) missions exploring the Jovian icy moons (Heggy et al 2017); and are all examples of how radar probing techniques have taken the search for subsurface volatiles on planetary surfaces from a local scale to a global one.…”