Astronomy Picture of the Day . APOD: 2006 January 1- The Largest Rock in the Solar System . ... 1.01.2006 . ... Credit: Voyager 1, NASA Explanation: There, that faint dot in the center - that's the largest rock known in our Solar System . It is larger than every known asteroid , moon , and comet nucleus . ... It used to be the largest rock of any type known until earlier this year. The Voyager 1 spacecraft took the above picture of the giant space rock in 1990 from the outer Solar System. ...