Ice Caps?
Hi al
Seems the case for ice-caps as explanations of the strong polar radar returns is bolstered, though there's still the chance for the "volatile" to be sulfur or sulfur-related. Why not both?
Here's an idea - sulfuric acid/water eutectic is liquid at 210 K, so its vapour pressure is very low... could there be pools of dilute acid around the polar caps? Perhaps that's the source of the observed water?