Mars rover Curiosity celebrates fourth anniversary

Today marks the fourth anniversary of NASA's rover Curiosity landing on the Red Planet and beginning its work to investigate Mars' history of habitability.
The last four years have been ones of great exploration, scientific and engineering achievements, and... well.... curiosity.
"Recently, NASA gave Curiosity the best anniversary gift it could hope for -- an extension of its mission for at least two more years," said Ashwin Vasavada,Curiosity project scientist for NASA, in a posted video.
"We'