Does anyone know what software was used to make this?

[White Miasma]

I found this world image on R Scott Bakker's website. It looks like some software was used to make it, perhaps similar to Fractal Terrains, but I find the locations of mountain ranges to be far more convincing (aside from the weird circles). Does anyone have an idea what software it might be?

I'd like to bring something like this into CC3 and work with it there.

[Diamond]

It really could be anything - I could duplicate this style with photoshop, and I've even seen people use Paint to make similar maps.

The circles are (I believe) impact craters from ancient wars against the alien Inchoroi. Awesome, awesome books.

[johnvanvliet]

as above could be anything

with a lo res image it is hard to tell.
The mountains "look" to be a fractal flame that has been pasted along a curve in something like inkscape ,or Gimp, or photoshop .

[Midgardsormr]

I made something similar in Illustrator a while back, too. Although it had an order of magnitude less detail than that one.