三月26，2009：2004年1月的时候，美国国家航空航天局（NASA）的勇气号和机遇号探测器在火星上登录。它们主要用于执行为期三个月的简短任务，以告诉我们这颗行星上水资源的情况以及曾经是否有生命存在于此。5年多过去了，它们两依然在这颗红色星球上流浪，这种传奇一般的成就改变了火星探测。

看这篇文章“勇气号和机遇号任务帮助我们开创了一个全新的学科——机器人现场科学”，火星探测任务的主要调查员Steve Squyres这样说，“它们教会我们怎样组织科学家和工程师的大团队，从而可以操纵遥远星星上的机器人。我们都需要学习怎样长年有效地合作，从而使这两个火星车找到最可能的新发现。”

右图：机遇号火星车[更多]

这个团队依然在努力。

近五年间这些太阳能驱动的机器人完成的非凡发现中：火星并不总是像现在这样寒冷干燥。 也许它不是世外桃源，但它有水也足够温暖来孕育生命。

火星探测任务的成员当然也知道千里之外调遣火星车的危险。他们不止一次停下火星车。“我们现在知道了怎样顺利地通过沙丘和石堆，” Squyres说， “也许更为重要的是——怎样避开它们。 我们把五年来的经验转换成全新的改进过的地图和驱动软件，以帮助我们完成剩下的任务和将来开发火星车。”

满怀希望的计划者们已经着手孪生火星车的将来， 设想它们会继续开路， 但也承认其中之一或者全部都可能在任何时间结束使命。 毕竟， 这些火星车还不完美。自从2006年 “勇气号”的一个轮子被堵塞后，它已经开始倒过来走， 一根破损的电线也阻碍了“机遇号”的一支机器手臂的运动。

待续...

Provided the twins hold up a while longer, here are the latest plans:

Opportunity, "the lucky vehicle since day 1" according to Squyres, has been crater-hopping since the beginning of the mission and is now heading south to the largest crater yet. The Endeavor crater is 20 km in diameter and 100s of meters deep.

"We'll have to double the odometer reading on a five year old vehicle to get there," says Squyres. "And it will take at least two years to reach it. [100 meters per day is an average day for Opportunity.] It'll be a long march across the plains, but it will be well worth it. The deeper the crater the older the history of Mars we can look at."

上图：The long march." Opportunity looks back on its own tire tracks en route to Endeavor crater. [更多]

Ray Arvidson, deputy principal investigator, elaborates: "Endeavor is an intriguing target because the rocks close to it look different from the ones surrounding the other craters Opportunity has visited. Part of Endeavor crater's rim is sticking up – Mars' ancient bedrock exposed -- and rocks nearby may be suggestive of acidic lakes on Mars' surface billions of years ago."

And what about the other twin?

"Spirit is the more challenging rover to operate," says Squyres. "There's not as much wind at its location to clean the solar arrays, and that affects the vehicle's power. Also, Spirit has to travel a more challenging terrain. The rocks and loose sand at Spirit's location are treacherous. Of course, to top it all off, Spirit is driving backwards.

右图：Sticky dust on Spirit's solar panels has reduced power to the rover. [更多]

Luckily, Spirit's landing site features a compact geology with enormous diversity and variability in a small area."

Spirit is now creeping steadily along a route to von Braun, an interesting looking mesa-shaped cap-rock that stands only about 250 meters away but will take months to reach. Then Spirit will head to a 30-meter diameter pit that may be a volcanic explosion crater -- and perhaps a location for hydrothermal activity.

"Because of the geology of its surroundings, Spirit specializes in looking for evidence in the rock record of water-charged explosive volcanism," says Arvidson. "Such areas could have once supported life."

"Home Plate, where Spirit spent the winter, is a volcanic structure eroded down so we can see the layers," explains Arvidson. "And we think von Braun and the neighboring Goddard structure may be made of the same stuff."

The Mars Exploration Team members have high hopes for the rovers to achieve all these ambitious goals but are mindful of the twins' limitations.

"We have no way of knowing what the future holds for the rovers at this point," says Squyres. "The mission could easily end tomorrow. But, the miracle could continue."

下图：Sunset on Mars, recorded by Spirit in 2005. [更多]

Arvidson recalls the day, over five years ago, when Spirit first touched down on the red planet.

“I was on a plane on my way back from Hawaii, headed to the Los Angeles airport, when Spirit was due to land. I just had to know if the rover had made it, so I asked the pilot to radio ahead to air traffic controllers and find out if Spirit had landed safely. I was overjoyed when he did so and confirmed that Spirit was sitting on Mars' surface, ready to go!"

Spirit is still going, Opportunity is still going, and Arvidson is still overjoyed.

Science@NASA原文