Yes, the convex appearence is entirely an illusion, as far as I can see. OK, if these are not dunes then this does not rule out other geological processes. As to the JPL quote, unless I can read it for myself I can't place it in context. But science by press release is a very dangerous thing. You may (or may not) remember the infamous statement in a popular NASA book after Mariner 2 that spoke of carbonhydrates on Mars, thus giving support to a whole generation of Velikovskyites.

Give a link to the press relase and I can comment. Incidently I have worked on the ground in deserts on Australia (Great Victoria, Simpson, and Strzelecki, the US (southern Utah) and South America (Atacama and the Altiplano). As I child I did travel through Jordan but I am not sure I can include that

Jon