The Number of the Day: 16,000

Related Link: Vacation to Mars: Photos of Antarctica's Dry Valleys, by Ransom Riggs
[Source: National Geographic Answer Book: Fast Facts About Our World (available for preorder). See previous Numbers of the Day here.]
Related Link: Vacation to Mars: Photos of Antarctica's Dry Valleys, by Ransom Riggs
[Source: National Geographic Answer Book: Fast Facts About Our World (available for preorder). See previous Numbers of the Day here.]