need some tips for mars

I am kinda stuck in this situation…
If you see this image, I am happy with the look and feel of it. Problem is, I used a insane resolution of 2019 x 2019 of just a few meters. (imagine, that I need to add a 2KM landscape)
To have an idea about the size. The default mannequin is almost as high as curiosity.

If I zoom I still get blobby rocks…I really wonder what the workflow is to add some reall nice details.

Here, I tried the folliage tool to add some details, but then again, the rocks still not really blend well. ( I am talking about the slates here)

I am looking for tips, ideas, what do to here. How can I get the detail that the first image suggest??
best regards! T