On the left is a picture from the Curiosity rover of a dry streambed at Gale Crater, Mars. On the right is a picture of some curious people in a dry streambed in the Atacama Desert in Chile, Earth. Notice anything similar? The fact there was water on Mars has been known for a while. We've seen evidence from orbiting crafts and the Opportunity rover landed right in front of a bank of exposed sedimentary bedrock. In 2008, the Phoenix lander saw a substance that had to be frozen water, not frozen carbon dioxide. It's so expected to find signs of water that month after landing, the Mars Science Laboratory rolls across a dry stream on Mars and everybody goes, "Ho hum." Not me. This is a freakin' dry streambed on Mars! You can even see where the running water has had time to undercut the Martian rock. Small round pebbles line the bed. I've hiked this dry streambed. I'm blown away.