Who's got the biggest volcanoes - Mars or Earth? Find out that answer and more as James Williams poses 3 questions to a scientist who knows.
Added: Feb 10, 2009
Views: 11326 Views
Runtime: 02:30
ATTENTION! We recently updated our privacy policy. The changes are effective as of September 10, 2008. To see the new policy, click here.
Questions? See the policy for the contact information.
Copyright © 2009 Discovery Communications, LLC. The number-one nonfiction media company.