less nuclear material to sustain it , and cooled and stopped spinning, and Mars lost it's magnetic field...(did they find volcanic rocks with polarized magnet alignment?, I though they did)...Well once the magnetic field was gone..the atmosphere heated up and started to boiled off, an the ocean's water...I wonder how much we got of Mar's ocean.. Post a comment CNN welcomes a lively and courteous discussion as long as you follow the Rules of Conduct set forth in our Terms of Service . Comments are not pre-screened before they post. You agree that anything you post may be used, along with your name and profile picture, in accordance with our Privacy Policy and the license you have granted pursuant to our Terms of Service . About Light Years strives to tell the stories of science research, discovery, space and education. This is your go-to place on CNN.com for today's stories, but also for a scientific perspective on the news and everyday wonders. Come indulge your curiosity in all things space and science related, brought to you by the entire CNN family.