走，去火星！

ByAlana+Semuels+++陈一榛

One day， when earth is destroyed by war or rising seas or a wayward1） asteroid2）， humanity will be extinguished—and along with it reality television， baseball stadiums， and thousands of recipes for guacamole3）， with and without peas.

太空探索技术公司开发的名为“Dragon”的宇宙飞船

Unless， that is， weve established a colony somewhere in space.

That idea may sound far-fetched4）， but scientists are working hard to make it a reality. What would it take， and how might we use the resources beyond Earths atmosphere？ I recently talked with aerospace engineers， entrepreneurs， and researchers to find out what our future in space will look like， in the near term and in centuries to come.

Fast Flights高速飞行

Private aerospace companies are developing reusable spacecraft， which will dramatically cut the cost of launches， because we wont need to build a new vessel each time we want to leave Earths atmosphere. Elon Musks SpaceX， for example， is on the brink of5） launching a reusable spaceship. Such vessels may soon make commercial spaceflight possible： Companies such as Virgin Galactic and Xcor are already accepting reservations for suborbital flights.

Such flights will be quick—Xcors will last about half an hour， Bryan Campen， a spokesman for Xcor， told me. Passengers can expect to be in zero gravity within five minutes of takeoff. After floating for another five or so minutes， they will descend back to Earth， experiencing 30 seconds of teeth-gnashing6） 4G reentry—about the same as on an intense roller-coaster ride—before gliding to the ground. These flights will take off and land in the same spot， but within a few decades， spaceflight could become the fastest way to travel internationally—making it possible to get from New York City to Tokyo in 90 minutes， Campen said.

Crowded Skies 拥挤的天空

As the cost of launching rockets comes down， more people will be able to participate in aerospace ventures. Already， universities and research groups can send up CubeSats—satellites about the size of a bread box—for as little as $100，000， a fraction of the tens of millions of dollars a satellite launch usually costs.

As more organizations send satellites into space， however， collisions become more likely. In 1967， 10 years after Sputnik 17）s launch， about 2，500 objects （satellites， used rockets， and debris） were orbiting Earth; now there are more than 20，000， according to Colonel8） John Giles， the commander of the Joint Space Operations Center， which identifies and tracks objects in space. A two-centimeter piece of debris can cause as much damage to a satellite in space as a speeding Jeep would on Earth， Giles told me. The U.S. military is developing a “space fence”—a radar-like system expected to be operational by 2018—to warn of impending collisions and beginning to plan for a time when adversaries might try to take out satellites that are crucial for GPS and communications.

Men on the Moon 人类登月

Though no American has set foot on the moon since 1972， China recently landed a rover there and plans to eventually set up a permanent lunar base. In many ways， the moon is a good place for a colony—it has water， and its soil could be mined for minerals and oxygen. The moon would also make a good jumping-off point9） for exploring the rest of the solar system. Its gravity is about one-seventh that of Earth， so launching spacecraft there would require much less energy.

Chris Impey， an astronomy professor at the University of Arizona and the author of Beyond： Our Future in Space， thinks we may one day build a “space elevator” on the surface of the moon in order to make lunar launches even easier. The idea sounds like something out of a Roald Dahl10） book： A giant tapered11） cable made of superstrong material would reach 35，000 miles into space. Solar-powered elevator cars would climb up the cable， delivering spacecraft into the moons orbit. “Serious engineers have been investigating this for half a century，” Impey said. “We could almost build it right now.”

Missions to Mars … 火星任务

Many scientists think Mars， which has large underground glaciers， could be our best bet for a permanent colony on another planet. But the obstacles to living there are daunting. Humans cant breathe the air， and the planets frequent dust storms would make farming difficult. Solar radiation is another problem， and sending messages to Earth （via radio waves traveling at the speed of light） can take more than 20 minutes， depending on where the planets are in their orbits.

Still， scientists， architects， and engineers are brainstorming ways to overcome those obstacles. ZA Architects， a Ukrainian firm， has drawn up plans for structures made out of Martian soil; robots could be sent ahead to build them. Other researchers propose inhabiting Marss lava12） tubes—underground caverns likely formed by volcanoes—since the tunnels also provide protection from solar radiation and dust storms and would keep the temperature relatively constant. And NASA is testing an inflatable13） habitat that could be deployed on the surface of Mars.

If a group of humans were to live on Mars for centuries with little or no contact with Earth， they would likely evolve， eventually becoming a different species， Impey told me. Because Mars has less gravity， scientists believe humans would slowly grow taller and their cardiovascular14） systems would become weaker. Theyd also have less body hair （because theyd have to stay indoors or wear space suits， they wouldnt need the protection from the elements15））， and their controlled diet might result in smaller teeth. But thats assuming， of course， that humans can reproduce in Marss gravity—an untested proposition.

... And Beyond 向深空探索

In or near the moons orbit， there exist a few spots， called Lagrange points16）， where an object is pulled neither to the moon nor to Earth. A space station orbiting one of these points could stay in place for a long time without floating away.

Eventually， Pat Troutman told me， one of those areas could serve as a harbor for ships going out farther into the universe， a sort of Rotterdam of the solar system. Resupplying and refueling would be costly from Earth， but， aided by robots， astronauts could pull a large boulder17） from an asteroid， tow it to a stable area， and mine it for water and oxygen， which could be turned into rocket propellant， Troutman said.

The dwarf planet18） Ceres， the largest object in the asteroid belt， may have big reserves of water， making it a potential base for more refueling， Troutman told me. And if Mars turns out to be uninhabitable， the Jovian19） system—Jupiter and its moons—might be a good alternative， he said. It， too， has water， and is largely protected from the suns radiation.

The universe contains an almost incomprehensible number of stars—our galaxy alone has hundreds of billions， and there exist hundreds of billions of galaxies—and an even greater number of planets. Current technology isnt very good at determining which of those planets might be habitable—or already inhabited， Sara Seager， a professor of planetary science and physics at MIT， told me. But our view of the galaxy could become a little clearer in 2018 with the launch of the $9 billion James Webb Space Telescope20）. It will sit 1 million miles from Earth， where it will search for gases that look out of place in the atmospheres of other planets， signaling vapors that might be produced by other life-forms.

Sending a probe is likely the only way to know for sure whether extraterrestrial species exist. But even traveling at one-tenth the speed of light， which some physicists believe might be possible， getting to the nearest star—25 trillion miles away—would take about 43 years.

Some physicists theorize that humans could one day get to far-off stars faster by warping21） space-time—essentially pushing a spacecraft forward by rapidly expanding the empty space behind it. The theory is unproven， and the process would require massive amounts of energy. Still， many scientists remain optimistic about the possibility of a manned mission beyond our solar system. “I have no doubt its going to happen，” Troutman said. “Just maybe not in my lifetime.”

如果有一天地球由于战乱、海平面升高或是横冲直撞的小行星而毁灭，人类也将面临灭绝，随之消失的还有真人秀节目、棒球场以及成千上万的鳄梨调味酱食谱——有没有豌豆的都算上。

除非，也就是说，我们已在太空的某一处建立了一个殖民地。

这一想法也许听起来不切实际，但是科学家们正努力使之成为现实。实现这一梦想需要什么？又该如何使用地球大气层之外的资源呢？最近，我与航空航天领域的工程师、企业家和研究人员进行了交谈，试图弄明白短期内以及以后的几百年里我们太空探索的未来会是怎样的。

私营航天公司正在研发可重复利用的航天器，这样会极大地降低发射成本，因为我们将不用每一次想要离开地球大气层时都造一个新的飞船。例如，埃隆·马斯克的太空探索技术公司（SpaceX）即将推出可重复使用的宇宙飞船。有了这样的飞船，商业太空旅行很快就可能成为现实：维珍银河公司和Xcor航天公司等都已经接受亚轨道旅行的预订。

Xcor航天公司的发言人布莱恩·坎彭对我说，此类飞行的速度会很快，Xcor公司的飞船将飞半个小时左右。乘客有望在起飞后五分钟内体验到失重状态，之后漂浮五六分钟，然后下降返回地球，在重返大气层时要体验咬紧牙关承受四倍重力的感觉，仿佛坐在飞驰的过山车上一般，最后滑翔落地。这样的飞行会在同一个地点起飞和降落，但是要不了几十年，太空旅行将会成为国际旅行最快捷的方式——从纽约到东京只需90分钟是有可能实现的，坎彭说道。

随着火箭发射成本的降低，越来越多的人可以参与到太空探索中来。各个大学和研究机构已经可以发射魔方卫星——只有面包盒大小的卫星——花费低至十万美元，只是发射一个普通卫星所花费的成千上百万美元成本的皮毛。

然而，由于越来越多的组织发射卫星到太空，卫星发生碰撞的几率也随之增大。1967年，“斯普特尼克1号”发射升空十年后，大约2500个物体（包括卫星、火箭残骸、碎片）在地球轨道运行。而按照联合太空作战中心的指挥官约翰·吉尔斯上校的说法，如今这一数量已达到20000个。该中心负责确认并追踪太空中的物体。吉尔斯告诉我，太空中两厘米大小的碎片撞击卫星所造成的破坏与地球上一辆高速行驶的吉普产生的破坏相当。美军正在研发 “太空篱笆”，这是一种类似雷达的系统，有望在2018年前运行，其目的在于对即将发生的碰撞发出警告。另外，军方也开始制定计划，以便在敌人试图击落对GPS系统和通信极为重要的卫星时予以应对。

自1972年之后就没有美国人登陆过月球，但中国近期却把探测车送到了月球上，并计划最终建立永久的月球基地。从很多方面来讲，月球都是个建立殖民地的好地方——那里有水，那里的土壤中含有可供开采的矿物质和氧。月球也可作为探索太阳系其他星球的一个很好的出发点，其重力仅为地球的七分之一，因此在那里发射宇宙飞船所需的能量要少很多。

克里斯·殷匹是亚利桑那大学的天文学教授，也是《地球之外：我们在太空的未来》一书的作者，他认为有一天我们会在月球表面建一个“太空电梯”，以使在月球上发射宇宙飞船更容易。这个想法听起来像是出自罗尔德·达尔的书：一条由超强材料制成的巨型锥形电缆通往35000英里深处的太空。太阳能驱动的电梯轿厢沿着电缆爬升，将航天器运送入月球轨道。“正儿八经的工程师们研究这个都有半个世纪之久了，” 殷匹说，“我们眼下几乎都能把它造出来了。”

很多科学家认为，火星地表下含有大量的冰川，会成为我们在另一个星球建立永久殖民地的最佳选择。但是在火星上生活面临的障碍之大令人畏惧。人类无法呼吸那里的空气，火星上频繁发生的沙尘暴会使农业耕作困难重重。太阳辐射也是个问题。向地球传送消息（通过无线电波以光速传送）要超过20分钟，时间的长短还要取决于这两颗行星处在各自轨道的什么地方。

然而，一些科学家、建筑师以及工程师们正在集思广益，想办法克服这些障碍。乌克兰的ZA建筑师事务所已经起草了用火星土壤建造房屋的方案，人类会率先发射机器人去建造。其他研究人员提出在火星熔岩管道——可能是火山喷发形成的地下洞穴——里面居住，因为这些管道也能保护人类不受太阳辐射和沙尘暴的侵害，并且能保持相对恒定的温度。此外，美国宇航局正在测试一种充气式居所，可部署到火星表面上。

殷匹还告诉我，如果一群人在火星上居住长达几个世纪，与地球毫无联系或者联系甚少，那么他们很有可能进化，最终成为不同的物种。由于火星的重力更小，科学家认为人类会慢慢长得更高，心血管系统功能会变得更弱。他们的体毛也会越来越少（他们因为不得不待在室内或穿着太空服，所以就不需要体毛来保护自己不受周围环境的伤害），同时受控的饮食也会导致他们的牙齿变小。当然这只是建立在人类能够在火星的重力环境中繁衍后代的假设上——这是个未被验证的设想。

在近月轨道上或附近，有几个点叫拉格朗日点，在这些点上的物体既不会被拉向地球，也不会被拉向月球。围绕这样一个点运行的空间站可以长时间停留在合适的位置，而不会漂移到其他地方。

帕特·特劳特曼对我说，最终这些区域中的某个可以作为飞船深入宇宙的港湾，相当于太阳系中的鹿特丹港。从地球上对飞船再次提供补给和补充燃料的花费会很大，但是在机器人的协助下，宇航员能从小行星上搬走一块巨石，将之牵引至稳定地带，从中开采水和氧气，这些物质可以进而转化成火箭的推进燃料。

谷神星这一矮行星是小行星带中最大的一个星球，可能有丰富的水储备，这使其可能成为一个补给燃料的基地，特劳特曼告诉我。他说，如果最终发现火星不适合人居住，那么木星系统，也就是木星及其卫星，也许是另一个不错的选择。木星上同样有水，而且很大程度上不受太阳辐射的影响。

宇宙里恒星的数量多到几乎无法想象，光是银河系就有上千亿颗恒星，而星系又有上千亿个，行星的总量就更多了。麻省理工学院的行星科学与物理学教授萨拉·西格尔告诉我，目前的技术手段还不太能够确定哪一个星球适宜居住，或是已经有生命定居。但是随着2018年耗资90亿美元的詹姆斯·韦伯太空望远镜的发射，我们对银河系的观测会更加清晰一些。这台太空望远镜会坐落在与地球相距100万英里的地方，在那里探测其他星球上看起来与其本身的大气格格不入的气体，这可能就是由别的生命体产生的气体在向我们发信号。

发射探测器很可能是确定是否有外星生命存在的唯一途径。但即使以一些物理学家认为可行的光速的十分之一的速度飞行，到达最近的恒星——25万亿英里之外——也需要花费大约43年。

一些物理学家从理论上推测，总有一天，人类可以通过扭曲时空的方式以更快的速度到达遥远的星球。扭曲时空本质上就是通过快速扩大飞船身后的空间而促使其前行。这一理论并未得到证实，而这一过程会需要极大的能量。然而，还是有很多科学家乐观地认为，太阳系之外的载人飞行是可能的。“这一定会发生，对此我深信不疑，” 特劳特曼说，“只是我在有生之年可能无法看到了。”

1. wayward [?we?w?（r）d] adj. 难以控制的;不稳定的;不规则的

2. asteroid [??st??r??d] n. [天]小行星

3. guacamole [?ɡwɑ?k??m??li] n. 鳄梨调味酱。本文在鳄梨调味酱之后加了句“有没有豌豆的都算上”，这源于2015年《纽约时报》（The New York Times）的“鳄梨调味酱门”事件。2015年该报在自己的推特账号上发布了一个讲述做鳄梨调味酱时加入豌豆的食谱的链接，并配文字说明“Add green peas to your guacamole. Trust us”。这遭到很多读者的负面评论，连奥巴马都发推特说豌豆与鳄梨调味酱不搭。

4. far-fetched [?fɑ?（r）?fet?t] adj. 牵强的，靠不住的

5. on the brink of：濒于，即将发生

6. gnash [n??] vi. 咬牙

7. Sputnik 1：“斯普特尼克1号”，苏联于1957年发射的人类第一颗人造地球卫星

8. colonel [?k??n（?）l] n. （陆军、空军或海军陆战队的）上校

9. jumping-off point：起点，出发点

10. Roald Dahl：罗尔德·达尔（1916～1990），挪威籍的英国杰出儿童文学作家、剧作家和短篇小说作家，代表作品有《查理与巧克力工厂》（Charlie and the Chocolate Factory）等。

11. tapered [?te?p?（r）d] adj. 锥形的

12. lava [?lɑ?v?] n. [地]熔岩

13. inflatable [?n?fle?t?b（?）l] adj. 可吹胀的，可充（或打、吹）气的

14. cardiovascular [?kɑ?（r）di???v?skj?l?（r）] adj. 心血管的

15. element [?el?m?nt] n. （人或物的）自然环境

16. Lagrange point：拉格朗日点，指在两大物体引力作用下能使小物体稳定的点，于1772年由法国数学家拉格朗日推算得出。

17. boulder [?b??ld?（r）] n. 巨砾;漂砾;（由于气候或水侵蚀而形成的）卵石

18. dwarf planet：矮行星，太阳系外围较小的天体，体积介于行星和小行星之间，目前发现的矮行星包括谷神星、冥王星、阋神星、鸟神星和妊神星。

19. Jovian [?d???vi?n] adj. [天]木星的

20. James Webb Space Telescope：詹姆斯·韦伯太空望远镜，是哈勃太空望远镜的继任者，将在2018年10月发射。

21. warp [w??（r）p] vt. 使翘曲