Comet ISON will approach the inner solar system late 2013. In early October 2013, ISON will be closer to Mars than it will ever be to Earth (?). Around November 27 of 2013, c2012 S1 will be orbiting around the sun and it will start its approach to Earth. Provided it is not altered by Sol, comet ISON will create a spectacular view. Some astronomers claim it will be as bright as the moon.
Animation created with Celestia
The orbital pattern is not mine