Bizarre Mars 'Ripples' Offer Window into Red Planet's Past

Mars harbors a mysterious kind of dune-like structure that's unlike anything seen on Earth, a new study reports. These unusual sandy ripples might yield insights about how Mars has evolved over time from a potentially habitable world to the harsh, dry planet we know today, researchers added. On Earth, wind blowing over sand causes the formation of either small ripples a few inches to a foot (30 centimeters) long to large dunes that can stretch for miles.