Samples of altered pillow basalts and hyalotuffs were collected from a volcanic tuya and hyaloclastite ridge in western Iceland. Altered basaltic material from regions such as Hlöðufell tuya and Thórólfsfell ridge may be similar to the altered basaltic surface fines on Mars. Geochemical and mineralogical analyses have been performed on the Icelandic samples in order to characterize the properties that distinguish palagonitization from other forms of low temperature alteration in this environment. Major elements were measured using an electron microprobe and mienralogy was determined through X-ray diffraction and visible-infrared reflectance spectroscopy. The primary focus in this study was on the <2 μm size fractions of the Hlöðufell altered pillow basalt and Thórólfsfell palagonitic tuff samples. Both volcanic alteration products contain at least some smectite and serpentine clay minerals, as well as poorly crystalline layer silicates. The palagonitic tuff contains more crystalline clay minerals, fewer nanophase iron oxides/oxyhydroxides, and has a higher A1/Fe ratio compared to the altered pillow basalt. Spectra of the <2 μm fractions of both Icelandic samples share similarities with the extended visible region spectra of the bright martian soils measured by Pathfinder and the infrared spectra of the martian dust measured by spectrometers on the Mariner missions.
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Bishop et al. (2002) studied this question.