SINCE landing on Mars last month, Nasa’s Curiosity rover has grabbed headlines with a series of spectacular images of the red planet’s surface.But Curiosity is not the only spacecraft currently wandering over Mars - Opportunity is still going strong, more than eight years after it touched down on the planet. And the elder statesman of Mars rovers launched a challenge to its younger cousin this week, beaming back a series of fascinating pictures of the landscape around it.Most striking is a photograph which shows small rock fins strewn across the landscape, looking exactly like a stretch of savannah here on Earth. The area on the western rim of Endeavour Crater is believed to be comprised of clay minerals.Another picture gives a panoramic view of the region where the rover spent its 3,000th Martian day, or ‘sol’.And a third shows the shadow cast by Opportunity itself on the face of the planet.The rover landed on Mars on January 25 2004, and has been operating continuously since.Opportunity was originally intended to last just 90 days - it has now been transmitting data for over 3,100 days. It landed on Mars around the same time as Spirit, a near-identical rover which broke off communication with Earth in March 2010. –DM