my wife and I were on our way to Wendover Nevada. At 7:00 pm we were traveling west through the boniville salt flats.The mountain range behind Wendover was approx. 50 mi away. clear blue sky .The sun had just dropped behind mountains allowing us a spectacular view.we suddenly noticed at approx. 45 degree up looking west, just beyond mountains, we clearly abserved. what looked like a white plume from a large rocket with a ball at the top..it sat there not moving.. After 20 min it moved slightly to left then ascended straight up at great speed. The ball became COMPLETLY visable turned red,the white plume followed staying the same size as when it hovered. we cant get this out of our minds.