Been seeing theses at the planet I'm on. Don't recall having puffs before. They are not distant nebulae. These move and dissipate. Kind of like dust devils that aren't on the ground.
I think they've been there ever since Odyssey, on worlds of all types with a thin atmosphere. They do not seem to affect me when I drive the SRV through them but they are a nice environmental flourish. I have wondered if they were intended to be a test for larger features but no sign of that: they are all the same size.
They were much denser in the Beta, if you landed on the right planet and hopped in the SRV and built up a bit of speed you could get a real dust storm effect going, now they only appear as individual puffs floating around, although some can get quite large, but maybe in the future we will get more like this: