CaSSIS color and multi-angular observations of Martian slope streaks

Slope streaks are albedo features that form frequently on equatorial Martian slopes. Most slope dark relative to surrounding terrains, a minor fraction is bright, and there rare transitioning exhibit contrast reversal partway downslope. Their formation mechanisms physical surface properties not well understood. New observations acquired by the Colour Stereo Surface Imaging System (CaSSIS) board ESA's ExoMars Trace Gas Orbiter (TGO) provide insights into streaks' microstructure, roughness particle size ranges. Using multiple phase angle observations, we show substantially rougher possibly more porous than their bright counterparts, which likely composed of compact regolith. Color data in four wavelength bands suggest spectrally similar but larger particles. The comparison our orbital results laboratory measurements regolith analogs indicates particles within may be up factor granular material terrains. At one study site Arabia Terra, using complementary imagery from other orbiters, identify case where turned fully twenty-year period. These CaSSIS old streaks, formed deposition dust or decomposition aggregates smaller