Why doesn a terrestrial planet like Mars have a ring system?
Scott Preston, 8th grade, Charleston Middle School, Charleston, IL ANSWER: Maybe it did. Right now, it has just two little moons, Phobos and Diemos, which may be captured asteroids. Not a lot is known about how ring systems form around planets, but they may consist of crunched-up moons that were torn apart in a gravity tug-of-war between a planet and a larger moon. Or they may be made up of errant comets that were captured and ripped apart by a planet’s gravity. Earth may well have had a ring or rings in its past. The Cassini mission to Saturn will shed a lot of light on how ring systems form and are maintained when that spacecraft reaches the ringed giant in 2004.
