Make an object move in a circular motion HELP!

Hi there Corona Community!

I need help making a part of my game!  I need an object to move around a circle in a continuous motion.  When the screen is touched, the object will then go continuously in the other direction.  

To know what I need accomplished, check out the game below called “Circle Surfer”!

The little character rotating around the circle is exactly what I need done but when the user touches the screen it reverses directions! Thanks in advance!

https://itunes.apple.com/us/app/circle-surfer/id898607045?mt=8