New Horizons Mapping of Europa and Ganymede

Abstract

The New Horizons spacecraft observed Jupiter's icy satellites Europa and Ganymede during its flyby in February and March 2007 at visible and infrared wavelengths. Infrared spectral images map H2O ice absorption and hydrated contaminants, bolstering the case for an exogenous source of Europa's "non-ice" surface material and filling large gaps in compositional maps of Ganymede's Jupiter-facing hemisphere. Visual wavelength images of Europa extend knowledge of its global pattern of arcuate troughs and show that its surface scatters light more isotropically than other icy satellites.

Antarctica as Model for the Possible Emergence of Life on Europa

“…They match the distribution of an ultraviolet absorber that was suggested all the way back by the Voyager data (McEwen, 1986). The New Horizons Mission on its way to Pluto has confirmed the patches of non-ice elements (Grundy et al, 2007). Based on combined spectral reflectance data from the Solid State Imaging experiment (SSI), the Near Infrared Mass Spectrometer (NIMS) and the Ultraviolet Spectrometer (UVS), it has been argued that the non-water ice materials are endogenous in three diverse, but significant terrains (Fanale et al, 1999).…”

ALMA Thermal Observations of a Proposed Plume Source Region on Europa

“…The grayscale values and approximate normal albedos correlate linearly with an R 2 of 0.92 and a standard deviation of 0.03, which we take as the statistical error in our albedos. As the phase integral of Europa is 1.01 (Grundy et al 2007), we take these normal albedos as approximate hemispherical albedos and use them in model calculations of solar flux absorbed across the surface of Europa.…”

Exospheric signatures of alkali abundances in Europa's regolith

“…In Figure 2, the surface distribution of the Na/K ratio R D peaks to values close to 10 at 270°W in longitude. This region matches the low albedo regions bearing the largest fraction of non-ice materials observed by Grundy et al [2007]. Since the sputtering yield is lower in those regions than in the rest of Europa's surface (see Cipriani et al [2008] for further explanations), the mass fractionation induced by the ejection is less efficient (the surface ratio is, therefore, assumed to be closer to the underground surface abundance ratio of 26 ± 2).…”

“…As was done by Cipriani et al [2008], we use energy distributions for sodium and potassium ejected by PSD similar to the sputtering energy distributions. The surface sputtering yield is taken as a weighted function of sputtering yields for pure ice and non-ice bearing materials present at the surface, assuming a non-ice fraction distribution derived from New Horizons/LEISA measurements by Grundy et al [2007].…”