
'Dog door' on Mars found by Curiosity rover is a rocky 'doorway into the ancient past,' NASA says
The strange door-like feature discovered in a martian cliff earlier this month is perfectly natural but provides a "doorway into the past", said NASA.
Mars, the Red Planet, is the fourth planet from the sun.
Related Topics: Curiosity Mars Rover Mission, ExoMars, India Mars Orbiter Mission, Mars Rover Opportunity, Maven Mars Mission