And...
One thing I should have emphasised. The Egypt study talks about penetration depths of a few metres to ~10 metres.
On Mars, to get below the ice we need penetration of a few km to ~10 km. To do this we will need lower frequencies, which gives blurrier images. (most noticable blur is in depth, spatial resolution will still be reasonable - hundreds of m to ~ 1 km is more than adequate for a first planetary-scale map, but might have trouble picking out details of channel beds)