Opportunity has made one of its greatest scientific discoveries so far. Clay minerals in a rock called Esperance clearly indicate that neutral water flowed across the rock some time in the first billion years of its existence.
The rock was found near Endurance Crater, and took seven attempts to analyse because it was partially covered in Martian dust.
The clay minerals are similar to one called montmorillonite. Formed under the influence of neutral water, this is significant because neutral water, which is similar to household tap water, is thought to be much more conducive to the chemistry needed for the origin of life.
Announcing the results, Steve Squyres, principal investigator for Opportunity, Cornell University, Ithaca, N.Y. said that, although they have talked in the past about finding water with Opportunity, really it was more like sulphuric acid.
As Mars turned into the desert planet we see today, so the water became more acidic. This happened because of evaporation, which left a higher concentration of minerals in the remaining water – rather like reducing a sauce to make it richer.
Neutral water dates from an earlier time on the planet, when it rained frequently bestowing a more Earth-like environment.
Although a first for Opportunity, this is not the first time that neutral water has been found on Mars. In March, NASA's larger, younger rover Curiosity found evidence for 'drinkable' water in clay minerals in Gale crater. "It is really striking to me, how similar the stories are for the rocks at Gale and Endeavour crater," says Squyres, comparing the two findings.
Opportunity is now heading for a 55-metre high outcrop called Solander Point. Averaging 50 metres per day, the team hope to get there before August.
Winter is approaching on Mars. If Opportunity reaches Solander Point's sloping sides, the solar panels can catch more of the low winter Sun. This could give them enough power to drive during the winter months.
In previous Martian winters, on flatter terrain, power levels have dropped so much that engineers have had to park Opportunity and wait for the cold weather to end.
Images show that Solander Point displays layered terrain. These layers preserve a record of Mars's changing climate throughout the planet's history, which Opportunity can read. Analysing such layers is similar to Curiosity's mission at Mount Sharp in Gale crater.
The longevity of Opportunity is astonishing. Designed to last for just 90 Martian days, it is now approaching its 3400th Martian day of operation.
It has lasted almost 40 times longer than its design lifetime. It was launched on 7 July 2003 and landed on 25 January 2004.
Considering the age of the rover, and the fact that its twin Spirit 'passed away' in 2010 during its fourth Martian winter, it seems prudent to start the celebrations now. Just in case.
“机遇号”目前已实现了它的一项最伟大科学发现。一块名为“狮石”（Esperance）的岩石里，其中的粘土矿物表明在这块岩石最初的10亿年中的某个时刻时在，曾有中性水从它上面流过。
这块岩石在“持久”陨石坑（Endurance Crater）附近发现的 ，由于有一部分在火星尘埃下面，通过七次尝试才将它分析出来。
这个粘土矿物与“高岭石”（montmorillonite）矿物质很相似。这种矿物质在中性水的影响下形成，具有重要意义，因为与家用自来水相似的中性水被认为更加有助于生命起源所需的化学物质的产生。
“火星”号的首席研究员斯蒂夫斯.奎尔斯（steve Squyres）在纽约州伊萨卡市的康奈尔大学（Cornell University）宣布研究结果时说，虽然过去他们宣布过“机遇”号发现水的事情，而事实上更像是硫酸。
由于火星变成了我们今天所见到的沙漠星球，因此，水的酸性更强。这是由于蒸发才公这种现象，而蒸发把高浓度矿物质留在了剩余的水中，这有点像酱油蒸发。变得更加浓稠。
中性水可以追溯到火星早期，那时火星上频繁地下雨，那时的大气环境与地球现在的环境很相近。
虽然这是“机遇”号第一次在火星上发现水，但这 却不是水第一次在火星上发现。在今年的三月份，美国宇航局的体积更大，设备更新的“好奇”号（Curiosity）火星车在盖尔陨石坑(Gale crater)的软土矿物中发现了可饮用水的证据。通过比较两次发现，斯奎尔斯说:“这真的令我很震惊，发生在盖尔陨石坑和持久陨石坑的事情是多么的相似 啊。”
“机遇”号现在正朝着五十五米高的被叫做索兰德高地的一块露出地表的岩石进发。它平均每天能前进五十米，所以它很有可能在八月前到达目的地。
火星上的冬天正在悄然来临。如果“机遇”号能到达索兰德高地(Solander Point)的斜坡，那么在冬天太阳电池板就能从高度角较低的太阳中吸收更多的能量。这就能给它们充足的能量在冬天的几个月里继续前行。
在火星上之前度过的几个冬天，“机遇”号都处于平坦地带，而功率电平降到了很低，工程师们不得不让“机遇”号停下来，等待着寒冷天气的结束。
图片显示索兰德高地呈现出层状地形。这些“机遇”号能研究的层状结构保存了火星整个历史进程中变化的气候的记录。“机遇”号分析这些层状结构的任务和“好奇”号在盖尔陨石坑中夏普山上的使命是相似的。
“机遇”号的寿命是惊人的。最初它被设计在火星上停留的时间仅仅是九十天（火星每天比地球长40分钟），而现在它即将要迎来它在火星上工作的第3400个日子。
“机遇”号在2003年7月7日发射升空，并于2004年1月25日着陆火星，已运行了接近四十倍于设计寿命的时间。
鉴于它现有的寿命和它的“孪生”火星车——“勇气”号在2010年即“勇气”号在火星上的第四个冬天期间“去世”。现在来进行庆祝似乎是很谨慎的。毕竟要以防万一嘛。