Before we switch to Scene 1, let's highlight the GroundBlockCutaway-Mars object on the far left by clicking on it. Now, load it into your computer's clipboard by copying it (Ctrl + C in Windows or Cmd + C on Mac). Why did we copy this one into memory? Because not only are we now able to copy the object to another scene, but its exact position. Since we're rolling from one scene to the next, we'll want to have the height of the first block of our next scene be the same height as the last block of this scene. And, since all of the blocks are the same height in the Start scene, why not copy the first block? Then its left-to-right position is also set and we won't have to move it.
Now, in the scene selection window (at the bottom of Buildbox), click on the button with a number 1 on it. You'll see an empty scene with our backgrounds in it, and a ghost image of our rover. Paste the GroundBlockCutaway-Mars object onto the stage by using Ctrl + V in Windows, or Cmd + V on Mac...