Step 1
Open a new document that is 500x500 pixels, RGB, and on a white background. Make sure your foreground color is WHITE and your background color is BLACK (d+x) and go to Filter>Render>Clouds, then Filter>Render>Difference Clouds, and you should have something like this
Step 2
Go to Filter>Sketch>Bass Relief
set Detail to : 13
set smoothness to : 3
And now you should have a rocky surface.
Step 3
If you like what you have now, you can just finish it off and keep it like this, if you want to make it look more impressive and alive, follow these next points
Go to Image>Adjustments>Invert or Ctrl+I
And the whole image should be reversed
And now go to Image>Adjustment>Hue and Saturation check the "Colorize" box and play around with the settings until you like the color of your martian surface
Good luck!
