There's actually a fully terraformed solar system you can activate by going into config/universe.cfg and commenting out "catalogs/planets/SolarSys.sc" and uncommenting //"catalogs/planets/SolarSys3000.sc" (by adding those slashes to the one and removing them from the other).
You can also do it yourself to Mars by changing its class to Terra and removing the entries describing its normal map (but leaving the ones that refer to the bumpmap).
Removing the bold stuff by itself would switch the planet to using procedural textures. If you want to have a terraformed appearance, you would need to do some more work, or use the script linked above.
Curiously Mercury is a satellite of Venus, Ceres is a satellite of Mars, the Moon appears to be much farther away than it should be (though I haven't actually checked), and Jupiter weighs 317 solar masses in Solar System 3000. Good luck landing on Europa.