Cometary science
彗星科学
Rosetta's stone
罗塞塔石碑
A European space probe has just arrived at its destination
一个欧洲空间探测器刚刚到达它的目的地
Aug 9th 2014 | From the print edition of The Economist
译者：yangsalt
THE maths, of course, were straightforward. The centuries-old celestial mechanics of Johannes Kepler and Joseph-Louis Lagrange made it clear that Rosetta, a European Space Agency (ESA) mission to intercept Comet 67P/Churyumov-Gerasimenko, should work. But in space, it is the engineering that leaves room for doubt. So for 23 nerve-racking minutes on August 6th, mission scientists waited for a signal of success to travel 405m kilometres from a probe that lifted off more than a decade ago. When the message did arrive, mindful of pan-European involvement in the project, the craft’s caretakers tweeted “Hello, comet!” in 23 languages.
数学当然是个很直白的东西。约翰尼斯·开普勒和约瑟夫·路易斯的有几个世纪时间古老的天体力学很清楚算出欧洲宇航局（ESA）的罗塞塔号会赶上67P/楚留莫夫－格拉希门克彗星。但是在太空里，这还需要工程师去论证。8月6日，参与任务的科学家们为这个大约十年前发射的走了405000000公里的探测器的成功信号等了焦急的23分钟。当信息传来时，整个欧洲参与到此项计划的关切的飞船管理人员，发了条用23种语言写的“你好，彗星！”微博。
It has been a busy year for Rosetta. The craft was roused from two-and-a-half years of hibernation in January, and has since been putting on the brakes and preparing for this week’s delicate manoeuvres. These have settled it into a roughly triangular orbit 100km ahead of its target.
This most recent stage of the journey, however, is not the most daring. That will come during a series of exquisitely timed moves over the next few months, as the craft spirals in to approach within 30km or so of its objective. From this vantage, it will survey 67P’s rugged terrain in order to select a landing site for Philae, a lander that it will release in November.
罗塞塔号今年很忙。这个飞船一月份从两年半的休眠期里唤醒，被制动然后等待这个星期的操作。这些把它送入了它目标前方100公里的一个类似三角型状的轨道里。现在这一步还不是整个过程最惊险的。最需要勇气的是几个月后，在飞船按螺旋形接近它目标三十公里处过程中的一系列精确的周期移动。从这个有利的地方，它可以观察67P的粗糙表面，为11月发射的菲莱登陆器选一个着陆地。
Project Rosetta is the latest in a series of cometary close encounters stretching back to Giotto, another ESA mission, which in 1986 passed within 600km of a more familiar comet, Halley’s. Sadly, the pictures Giotto sent back left much to be desired, but the intervening years have seen further missions with far better images, and in 2006 NASA’s Stardust probe even brought some comet dust back to Earth.
罗塞塔计划是一系列追赶卫星任务中继乔托号——1986年穿过我们熟悉的哈雷彗星600公里处的另一项ESA的任务——后最新任务。乔托号发回的照片不尽如人意，但是这些年间有了更进一步的任务，发回了更好的照片。甚至2006年NASA的星尘号探测器把一些灰尘带回了地球。
Those who take an interest in comets, however, want more detail than pictures, or even dust, can provide. So, in 2005, Deep Impact (a NASA mission, not the Hollywood film) sent a 370kg “impactor” careering into Comet 9P/Temple 1, to look beneath its surface. Stardust was then redirected to take a peek into the crater the impact created.
然而那些对彗星感兴趣的人，想要比照片甚至是尘土更多的细节。所以，在2005年深度撞击号（NASA的任务，不是那部好莱坞影片）向坦普尔1号彗星发射了一个370公斤的冲撞器来看看它表面以下的样子。星尘号又被送过去看看撞出的坑。
All these missions have shown that there is still much to learn from comets. They are now seen as “icy dirtballs”, dominated by rock, in contrast to the “dirty snowballs” hypothesised by Fred Whipple, an astronomer at Harvard University, in 1950. But the idea that the early Earth got its water from ice-laden comets ploughing into its surface is still popular. Indeed, some researchers believe comets also delivered the chemical ingredients of life.
这些任务显示出关于彗星我们还有很多需要探究。现在彗星被认为是一个主要由岩石构成的冰冷的土球。而不是1950年哈佛大学天文学家 Fred Whipple假设的盖着土的冰球。但是早期地球的水是由载满了冰的彗星带入的观点依旧很流行。一些研究人员确实相信生命化学物质是由彗星带入的。
Philae—along with Rosetta, which will continue its orbit and help with the measurements after Philae lands—will ride with the comet as it reaches perihelion, its closest approach to the sun, in about a year’s time. Philae will sample the surface, and also measure radio waves sent through the comet’s bulk to probe its interior in the way that X-rays probe a human body. Then, as 67P arrives at perihelion, more and more icy material will evaporate and escape from it as jets, and Philae should be well-placed to sniff out exactly what lies within.
带着菲莱的罗塞塔，会在菲莱登陆后继续环绕航行并进行测量，它会陪这个彗星在大约一年后到达离太阳最近的近日点。菲莱会在表面提取样本，向彗星发射电波来探测它的内部就像X光探测人体一样。之后，随着67P到达近日点，会有越来越多的冰升华，菲莱会被安置好来检测里面有什么。
From the print edition: Science and technology
译者注：1799年，罗塞塔石碑（Rosetta Stone）在埃及被发现。石碑上镌刻了三段分别用埃及象形文字、通俗体文字和希腊文书写文字。由于文字的内容完全相同，科学家终于在1822年破译出了古埃及的象形文字，打开了通向古埃及历史文明的大门。科学家希望“罗塞塔”号成为天文学的“罗塞塔”石碑，提供彗星保存了数十亿年之久的太阳系初期信息，通过研究这些信息，科学家可以打开通向太阳系古老历史的大门
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