Raycasting with mouse click, but nothing is happening

I am using the following code and when I click, nothing is displayed.

var hit : RaycastHit;

    if(Input.GetButtonDown("Fire1"))
    {
        var ray : Ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        if(Physics.Raycast(ray, hit))
            Debug.Log("Mouse Down Hit Terrain " + hit.point);
    }

I have a bunch of planes in my scene. Do I need to do anything special to make the raycast detect them?

I put a box collider down and clicked it, and that worked. So I guess I just need to have a collider on my plane.