A Momentous Crossing on Mars
by Richard A. Kerr 胡德良 译
| Today, scientists announced in a NASA teleconference that the veteran Opportunity Mars rover can now make a unique claim: Its 36 kilometers of roving has carried it across the most important geologic transition in the history of the Red Planet. Team members reported that analyses of a third-of-a-meter-long rock that they call Esperance (rendered here in exaggerated color) is rich in a sort of clay that could only have formed when lots of neutral-pH water bathed martian rock. Up to now, Opportunity had been finding only ancient rock leached by acidic brines far more hostile to life and ill-suited to nurturing the origin of life. So the rover has now sampled both sides of the momentous planetary transition from a wet, benign environment more than 4 billion years ago to a colder, drier, harsher one since then. NASA\'s Curiosity rover arrived on Mars last August to examine the same transition preserved in Gale crater but won\'t reach its target rocks until this time next year. | 今天，科学家们在NASA举行的一次电话会议上宣布说，有关资深的“机遇”号火星探测器，现在可以做出一项独一无二的声明：36公里的漫游使“机遇”号穿过了火星历史上最为重要的地质过渡带。研究小组报道说：他们将一块三分之一米长的岩石成为“埃斯佩兰斯（Esperance，图中颜色描绘得有些夸张）”，对该岩石进行的分析表明，其中富含一种粘土，只有许多pH值为中性的水浸泡火星岩石后才会形成这种粘土。此前，“机遇”号发现的只是由酸性海水过滤出来的古代岩石，而这些海水对于生命来说要险恶得多，不适合生命起源的产生。因此，从40多亿年前湿润温和的环境到之后的较冷、较干燥、较恶劣的环境，“机遇”号在火星关键的过渡带上采集了两边的样品。NASA的“好奇”号探测器于去年8月份到达火星，来考察盖尔陨石坑中相同的过渡带，但是直到明年这个时间，“好奇”号才能到达要考察的岩石。 |
译自：美国《科学》杂志网站（7 June 2013, 5:10 PM）
原著：Richard A. Kerr
