SSRSS [Stock Sized Real Solar Sytem] takes RSS [Real Solar System] (which replaces the game solar system with Eve, Kerbin, Duna, and others with a real scale model of the solar system) and scales the size back to that of the stock game (10x smaller) to make it easier/compatible with stock rockets. As a result you have Mercury, Venus, Earth, Mars and so on but at 1/10th (stock size) scale. If you were looking to have Duna, Eve, and whatnot but Kerbin with an Earth texture this mod isn't the one you are looking for (though in my opinion is much more fun than stock anyways).