Martian Valleys (IMAGE) Brown University Caption Extensive valley networks spidering through the southern highlands of Mars suggest that the planet was once warmer and wetter, but new research shows that water could still have flowed intermittently on a cold and icy early Mars. Credit NASA/JPL-Caltech/Arizona State University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.