In July of 1969, Neil Armstrong and Buzz Aldrin left the first human footprints on the moon. They also left two pairs of boots, a handful of tools, and four vomit bags. This lunar litter was far from the last space junk humanity has produced. In 2006, Suni Williams lost her camera while tussling with a stuck solar array on the ISS. And the following year, a similar job resulted in the loss of a bag filled with $100,000 worth of tools. These accidental satellites typically have short lifespans, before falling back to Earth and burning up in our atmosphere. However, other pieces of space junk, like SpaceX’s Tesla Roadster, will be stuck in their orbits for the foreseeable future.1969年7月，尼尔·阿姆斯特朗和巴兹·奥尔德林在人类历史上第一次在月球上留下了脚印。他们还留下了两双靴子、一些工具以及四个呕吐袋。这些月球垃圾远不是人类制造的最后一批太空废弃物。2006年，宇航员苏尼·威廉姆斯在国际空间站上处理卡住的太阳能电池板时丢失了她的相机。第二年，一次类似的任务又导致一个装有价值10万美元工具的袋子遗失。这些意外的“人造卫星”通常寿命很短，最终会坠回地球并在大气层中烧毁。然而，像SpaceX的特斯拉跑车这样的太空垃圾，将在可预见的未来长久地被困在轨道上。

In the early days of space travel, this kind of littering was largely considered inconsequential. But in today's crowded skies, orbital debris poses a serious threat to the thousands of satellites that underpin Earth’s vital technologies. Currently, there are over 131 million pieces of debris whipping around the planet at an average speed of 10 kilometers a second. This debris ranges in size from pieces as large as an entire bus, to those as small as a grain of sand. But roughly 1 million pieces are at least one centimeter across, which is large enough to severely damage most satellites. While losing any spacecraft is bad enough, the knock-on effects are even worse. When satellites crash into debris or each other, such as in 2009, when an American communications satellite collided with a defunct Russian satellite, they can explode into thousands of pieces. And if events like these happen often enough, the increase in debris could trigger a catastrophic cascade that researchers have named the Kessler syndrome: a runaway effect which could destroy untold numbers of orbiting spacecraft.在太空探索的早期，这种“乱扔垃圾”的行为被认为无关紧要。但在当今拥挤的太空环境中，轨道碎片对支撑地球重要科技系统的数千颗卫星构成了严重威胁。目前，有超过1.31亿块碎片以平均每秒10公里的速度围绕地球飞行。这些碎片大小不一，从一辆公共汽车那么大到一粒沙子那么小不等。其中大约有100万块直径至少一厘米的碎片，这已经足以严重损坏大多数卫星。失去任何一颗航天器本身已经够糟糕了，但连锁反应更为可怕。当卫星与碎片或彼此相撞时——比如2009年，美国一颗通信卫星与一颗报废的俄罗斯卫星相撞——会产生数千块新的碎片。如果此类事件频繁发生，碎片数量的增加可能引发一种灾难性的连锁反应，即研究人员所谓的“凯斯勒综合症”：一种失控的效应，可能毁灭无数在轨航天器。

But what does all this mean for people on Earth? Well, even if space shrapnel does take down a satellite, most debris burns up during re-entry. So theprobabilityof waking up to a spacecraft in your yard is very small. That said, some large specimens can survive the trip, such as the SpaceXCapsulethat landed in an Australian field in August of 2022. And the odds of something similar happening again grows alongside the amount of space junk. So how can we save our satellites and ourselves from all this trash?那么，这一切对地球上的人意味着什么呢？即使太空碎片击落了一颗卫星，大多数残骸在重返大气层时都会烧毁。所以，你早晨醒来发现院子里掉了一艘飞船的概率非常低。不过，也有一些体积较大的物体能在重返地球时幸存下来，比如2022年8月坠落在澳大利亚农田中的SpaceX飞船舱。而随着太空垃圾数量的增加，这种事情再次发生的几率也在上升。那么，我们该如何拯救卫星和自己免于这片“太空垃圾场”呢？

Part of the solution is to stop creating waste in space, but debris is generated in a lot of ways. In addition to collisions, solar radiation erodes spacecraft surfaces, motors spew slag, and satellite launches routinely abandon rocket bodies, covers, cowlings, and explosive bolts. Since 1957, we’ve ferried almost 16,000 satellites to space using thousands of disposable rockets. Researchers are finally experimenting with new systems that can send up over 100 satellites in a single rocket launch. Meanwhile, both NASA and private companies are working to prevent existing satellites from becoming junk by using servicer satellites to refuel, inspect, and repair them. But we also need to clean up the junk that's already up in orbit.解决问题的一部分是停止在太空中制造垃圾，但碎片的来源非常多。除了碰撞外，太阳辐射会侵蚀航天器表面，发动机会喷出熔渣，而每次发射卫星时，火箭的主体、保护盖、整流罩以及爆炸螺栓等部件都会被遗弃。自1957年以来，人类已通过数千枚一次性火箭将近1.6万颗卫星送入太空。研究人员终于开始尝试使用新系统——能在一次火箭发射中部署超过100颗卫星。同时，美国国家航空航天局（NASA）及多家私人公司正努力防止现有卫星成为太空垃圾，他们利用“服务卫星”为其加油、检查和维修。但我们也必须清理那些已经在轨道上的垃圾。

When a satellite is ready to retire, engineers can use controlled re-entry to intentionally burn it up in Earth's atmosphere. Ideally, this would happen as soon as a satellite is out of use, but outside the US, current guidelines allow defunct satellites to remain in orbit for up to 25 years, but this rule has barely been enforced. Beyond retired spacecraft, researchers have identified some particularly dangerous debris, so efforts could be made to tackle them first. Some debris experts have proposed using lasers, based both on Earth and in space, to nudge small debris to a higher, safer orbit or into the atmosphere. And private companies are attempting to use space tug boats to ferry large debris to less dangerous orbits.当一颗卫星准备退役时，工程师可以通过“受控再入”的方式，让它在地球大气层中有意烧毁。理想情况下，这应在卫星停止使用后立即进行。但除美国外，目前的国际准则允许报废卫星在轨道上停留长达25年，而这一规定几乎从未被严格执行。除了退役卫星外，研究人员还确定了一些特别危险的碎片，因此可以优先处理这些目标。一些碎片专家提议利用地面或太空中的激光，将小型碎片推向更高、更安全的轨道，或让其坠入大气层中燃烧。而私人公司则尝试使用“太空拖船”，将大型碎片拖往较不危险的轨道。

Whatever the solution, all these satellites and orbital debris reflect human consumption back on Earth. So if we want to keep using and exploring this final frontier, we'll need to get better at cleaning up our trash both up there and down here.无论采用哪种解决方案，这些卫星和轨道碎片都折射出人类在地球上的消费行为。如果我们想继续利用并探索这片“最后的疆域”，就必须学会更好地清理我们的垃圾——无论是在太空中，还是在地球上。