Europa's Sodium Atmosphere: An Ocean Source?

Composition and Detection of Europa’s Sputter-induced Atmosphere

“…5a. Leblanc et al (2002Leblanc et al ( , 2005 also predicted a globally averaged sodium concentration at the surface equal to ~0.01, and suggested that the observed sodium was sputtered from ice and not directly from a mineral or a salt. Recent modeling has improved on this description of the variability and on the Na/K ratios (Cipriani et al, 2008(Cipriani et al, , 2009.…”

“…The principal components in Europa's atmosphere have been calculated using one-dimensional DSMC (Shematovich et al, 2005;Shematovich, 2006) or two-dimensional DSMC (Wong et al, 2001;Smyth and Marconi, 2006) simulations. The threedimensional structure of Europa's atmosphere and its time variability with respect to its position within Jupiter's magnetosphere have been described using a test particle simulation for sodium Leblanc et al, 2002;2005;Burger and Johnson, 2004;Cassidy et al, 2008). Ip (1996) also applied a test particle approach for O 2 in Europa's atmosphere.…”

“…Sodium and potassium in Europa's atmosphere have been observed through the resonant scattering of sunlight as discussed. Potassium emission has been only been reported once (Brown, 2001), whereas sodium has been observed regularly since its discovery (Brown and Hill, 1996;Brown, 2001;Leblanc et al, 2002Leblanc et al, , 2005. Models of the sodium observations have been used to identify the spatial and temporal variability of Europa's extended atmosphere as a function of its orbital position (see Fig.…”

“…Comparing source and loss processes, it was suggested that the observed atmospheric sodium is mostly endogenic and therefore could be used as a tracer of Europa's interior composition and, possibly, its putative ocean. Leblanc et al (2002Leblanc et al ( , 2005) developed a three-dimensional test particle simulation of the three-dimensional structure of Europa's sodium atmosphere including its escape component, referred to as the sodium cloud. Sodium was ejected by sputtering and lost by returning to the surface or by ionization.…”

Exospheric signatures of alkali abundances in Europa's regolith

“…[3] In the present study, we use a refined 3D model of Europa's exosphere initially developed by Leblanc et al [2002Leblanc et al [ , 2005 and recently improved by Cipriani et al [2008]. This model accounts for non-uniform sources of alkalis at Europa's surface and allows us to describe the relation between exospheric and surface densities of the ejected material.…”