Emissivity and reflectance measurement at low and high T of different hydrous salts: a tool to study the surface of the icy planets

Abstract

Icy planets, in particular Jupiter’s moons, have attracted the scientific investigation due to the likely presence of oceans under crust which may potentially support life. Recent decision of NASA to go forward with plans for new mission to Europa provides strong incentives to deep the knowledge of the surface composition trough the analysis of exiting spacecraft data and telescopic observation. Really for the present-day researchers consider the beneath the icy surface of Europa is the most promising place to look environments suitable for life The non-ice Europa’s materials represent a question up to know not completely solved notwithstanding its relevance in planetary science and astrobiology. Preliminary data indicate that chloride and sulphate hydrates are important as extraterrestrial salts but a good database on the spectral features of some of them is lucking. The data known usually are restricted in a small frequency range and the collection of data is a function of temperature, atmosphere composition and are well grain distribution is very lacking. The collection of a library of possible non-ice spectra should be fundamental for a correct and exhaustive interpretation of the remote data. Recently Hanley et al (2016) [1] published reflectance spectra of hydrated chlorite salts, at room and low temperature to observe the effects of temperature on diagnostic spectral features. They showed that at low temperature increase the resolution of the spectra since the bands become narrower with sharper and better defined minima and showed distint spectra features which should be interesting to interpretate remote sensing data. About sulphate minerals there are a more extensive library, but a systematic study of the evolution of the spectra with chemistry, temperature and atmosphere composition is lacking. Moreover the published data refer to a limited spectra range, usually under 2.5 micron, where the sulphate signature is very poor (Dalton III B., 2003) [2]