奥陌陌猜想：向太空发射生命？
When the U.S. football field–size, cigar-shaped object 'Oumuamua entered our solar system last year, it didn’t just give us our first glimpse of an interstellar piece of rock.
去年，当美国发现的足球场大小、雪茄形状的物体“奥陌陌”进入太阳系时，它不仅仅是让我们第一次看到了一块星际岩石。
It also bolstered the plausibility of space rocks spreading life among the stars by ferrying microbes between distant star systems, according to a new study.
根据一项新的研究，这也支持了太空岩石通过在遥远的恒星系统之间运送微生物从而在恒星间传播生命的可能性。
“Life could potentially be exchanged over thousands of light-years,” says author Idan Ginsburg, a postdoc at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
“生命可能会在几千光年之外进行交换，”作者伊丹.金斯伯格说，他是马萨诸塞州剑桥哈佛-史密森天体物理中心的博士后。
The idea, known as panspermia, has been around for centuries.
这个被称为“生源论”的想法已经存在了几个世纪。
Some astronomers have even speculated that life on Earth was seeded by microbes that hitched a ride on debris ejected from another life-harboring world in the solar system, perhaps on meteorites from Mars.
一些天文学家甚至推测，地球上的生命是由微生物播下的，这些微生物搭上了太阳系中另一个存在生命的世界的碎片，可能是来自火星的陨石。
But it seemed improbable that life could have come from interstellar space.
但要说生命来自星际空间似乎不太可能。
Take computer simulations in 2003 by planetary scientist H. Jay Melosh, now at Purdue University in Lafayette, Indiana.
以2003年行星科学家h·杰伊·迈洛什(H. Jay Melosh)的计算机仿真为例。
The analysis revealed that about a third of the meteorites shot off Earth were eventually thrown out of the solar system by Jupiter or Saturn, but that the process took millions or tens of millions of years—a long stretch for even the toughest bugs or spores to be exposed to the vacuum and radiation of space.
分析显示分离地球的陨石里有大约三分之一最后会被木星或者土星抛出太阳系，不过这个过程会花去千万甚至亿万年—最有耐力的虫子或者孢子会在非常长的时间里暴露在宇宙的真空和辐射之中。
And vanishingly few rocks would ever be captured by some distant system, Melosh found.
迈洛什发现，几乎没有岩石会被某个遥远的星系所俘获。
The outlook improves if the receiving system is a binary star, which has a more complex gravitational field than the solar system.
假如接收的星系是双子星的话，希望就增加了，这种星系有比太阳系更为复杂的引力场。
Yet any system that’s good at capturing is also good at ejecting, meaning refugees from another system are far more likely to be tossed back out in a game of interstellar hot potato than to settle on a hospitable world.
不过任何善于接收的星系也善于拒绝，意味着来自另一个星系的难民远远会更有可能继续像烫手山芋一样被扔掉而不是定居在一个好客的世界里。
'Oumuamua is providing fresh hope for the idea of galactic panspermia.
“Oumuamua为银河生源论提供了新的希望。”
For the telescopic survey that found it, the Panoramic Survey Telescope and Rapid Response System, to have detected such an object in the region it had scanned, our Galaxy needs to have 1 trillion of them per cubic light-year, according to study published earlier this year.
根据今年早些时候发表的一项研究，对于发现它的天文观测系统来说，这个系统叫做泛星计画，要想在它所扫描的区域探测到这样一个物体，我们的星系需要每立方光年拥有1万亿颗这样的天体。
To fill space like this, every star in the Milky Way would have to eject 10 quadrillion such objects, and a few should be passing through our solar system at any given moment.
为了填满这样的空间，银河系中的每一颗恒星都必须喷射出十万亿个这样的物体，其中一些在每个给定的时刻都得要穿过我们的太阳系。
In the new study, Ginsburg, along with astrophysicists Manasvi Lingam and Abraham Loeb, also of the Harvard-Smithsonian Center for Astrophysics, calculated the chances of such objects delivering life to an alien world.
在这项新的研究中，金斯伯格与同样来自哈佛-史密森天体物理学中心的天体物理学家马纳斯维·林加姆和亚伯拉罕·勒布一起计算了这些天体将生命送到外星世界的几率。
A binary star such as Alpha Centauri would ensnare a few thousand rocks of 'Oumuamua’s size every year, and our solar system might snag one a century, the team estimates in a preprint posted last week on arXiv and in a forthcoming paper in The Astronomical Journal.
研究小组在上周发表在arXiv上的预印本和即将发表在《天文学杂志》上的一篇论文中估计，像半人马座阿尔法星这样的双星每年会捕获几千块与“奥陌陌大小相当”的岩石，我们的太阳系可能会在一个世纪内捕获一块。
The researchers then multiplied this capture rate by the number of stars an interstellar object will encounter before whatever bugs it carries all die.
然后，研究人员将这个捕获率乘以一个星际物体在其携带的任何昆虫全部死亡之前遇到的恒星数量。
If the objects move, like 'Oumuamua, at a velocity of 26 kilometers per second through interstellar space, 10 million of them will be captured somewhere in the Milky Way in a million years.
如果这些物体移动，像“奥陌陌”一样，以每秒26公里的速度穿过星际空间，在100万年后将有1000万颗物体被银河系的某个地方捕获。
“If you look at the galaxy as a whole, you expect this to happen fairly often,” Ginsburg says.
金斯伯格说:“如果你把整个银河系看作一个整体，你就会认为这种事情经常发生。”
Astronomer Jason Wright of Pennsylvania State University in State College says the analysis has merit: “For reasonable numbers, this suggests that planets and asteroids are commonly exchanged between stars.”
宾夕法尼亚州立大学的天文学家杰森·怀特说，这个分析是有价值的:“从合理的数字来看，这表明行星和小行星通常在恒星之间交换。”
But astronomer Ed Turner of Princeton University says the authors may be reading too much into the single example of 'Oumuamua.
但普林斯顿大学(Princeton University)的天文学家埃德·特纳(Ed Turner)说，作者可能对“奥陌陌”这个例子过分解读了。
“There’s no rigorous mathematical argument you can write about one event evaluated a posteriori,” he says.
“对于这种可能是后来才能验证的事情，不存在严格的数学论证，”他说。
And even if our galaxy is thick with 'Oumuamuas, they are unlikely vectors of panspermia, Melosh says.
而且即便我们的星系里遍布“奥陌陌”，他们也不太可能成为生源论的载体，迈洛什说道。
'Oumuamua is way too big to have been ejected from an inhabited planet, he says.
“奥陌陌”太大了，不可能是从有生命的星球上发射出来的，他说。
Still, Loeb says more data could settle where galactic panspermia is plausible.
尽管如此，洛布说，更多的数据可能会确定银河生源说的可能性。
Additional discoveries of interstellar interlopers would clarify their prevalence, and Loeb says the detection of life on other worlds would show whether it tends to cluster, as it would if it arose in one place and spread elsewhere by panspermia.
更多的星际闯入者的发现将会澄清它们的流行，洛布说对其他星球上的生命的检测将会显示它是否倾向于聚集，就像它会在一个地方产生，并通过泛生论传播到其他地方一样。
If so, he says, our entire galaxy might be considered biologically interconnected, its vast distances offset by vast spans of time and the vast number of objects that set out to cross the void.
如果是这样的话，他说，我们整个星系可能会被认为是生物学上相互联系的，它的巨大距离被巨大的时间跨度和大量准备穿越太空的物体所抵消。
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