资源环境科技发展态势分析平台

The Dorsa Argentea Formation (DAF) is an extensive Hesperian plains unit in the south polar region of Mars that was once ice‐rich and may still contain a substantial fraction of water ice. Given its 3.5‐Ga age, the possibility for massive ice in the DAF has significant implications for the preservation of volatiles during large obliquity changes. Here MARSIS and SHARAD radar sounder data are analyzed to determine whether massive water ice is present at depth by utilizing subsurface DAF reflectors to infer the loss tangent of overlying material. SHARAD (0.005±003) and especially MARSIS (0.009±006) loss tangent values are closer to those of dry sediment than to equatorial glaciers or the polar caps, but a fraction of remnant ice at depth may occur. Water ice is not the predominant component of the DAF, so much of the ancient ice has been lost during large obliquity changes over the past 3.5 Ga.