After two years of trekking across Mars' Meridiani Planum, NASA's Opportunity rover has passed the halfway point in its 12-mile journey to a monster crater. This 3-D postcard celebrates the milestone — and the scientists on the Mars rover team are celebrating as well. "The good news is that the worst part of the journey is over," Matt Golombek, a geologist at NASA's Jet Propulsion Laboratory, told me today. "The rest should be more fun than previous." The full 3-D panorama, based on image data collected on Aug. 19, gives you a sense of what's ahead for Opportunity, six and a half years after it landed on the Red Planet. (Be sure to put on your red-blue glasses, or check out the 2-D, black-and-white image.) The raised rim of 13-mile-wide Endeavour Crater, Opportunity's destination, is barely visible on the horizon. To get to this point, Opportunity had to make a circuitous detour around dune fields with impassably high ripples of sand. That detour added more than four miles to the estimated drive distance between Endeavour and Victoria Crater, the place from which Opportunity started out in September 2008. Now Opportunity has a straight shot ahead. Right in front of the rover, there's lots of interesting bedrock to study. After one or two miles of outcrops, there's about four miles of "almost smooth sand" leading to the crater's rim, Golombek said. A 100-yard-wide (90-meter-wide) impact site, dubbed Santa Maria Crater, serves as an intermediate point of interest. Golombek can't predict how long the rest of Opportunity's trip to Endeavour Crater might take, because there's no telling how much time scientists will want to spend studying the rocks and the crater along the way. "That's the problem with us scientists," he joked. But he's pretty sure the rest of the trip won't take another two years. "We have the opportunity — no pun intended — to get through the second half in less time than the first," Golombek said. He and his colleagues don't want to dawdle too much, because Endeavour Crater could well be the most scientifically interesting place Opportunity has a chance to visit. Observations made by instruments aboard NASA's Mars Reconnaissance Orbiter indicate that the crater's rim is rich in phyllosilicates — a type of clay mineral that is formed on Earth under wet, warm, non-acidic conditions. In short, just the kinds of conditions that are friendly to life. Opportunity already has found lots of evidence that water played a role in ancient Martian geology, but to date, the evidence indicates that the water was pretty acidic. Some earthly organisms can survive under such acidic and salty conditions, but it would have a pretty rough time. The area around Endeavour Crater would have been a more hospitable oasis, Golombek said. The rover's instruments are designed to focus on Martian geology rather than the bigger question about past or present life on Mars. But if scientists can learn more about the phyllosilicate-rich soil at Endeavour, that would help them with the planning for follow-up studies by future probes, such as NASA's Curiosity rover. That spacecraft, also known as Mars Science Laboratory or MSL, is due for launch next year and is expected to target phyllosilicates. "We have an opportunity with the rover here to beat MSL to the punch," Golombek said. No pun intended.
Check out our "Return to the Red Planet" special report to learn more about Opportunity and its sister rover, Spirit, which is currently in deep hibernation on the other side of Mars. If you feel like socializing, you can befriend me on Facebook or follow me on Twitter. And if you really want to be friendly, ask me about "The Case forPluto."