(单词翻译:单击)
SciShow Space is supported by Brilliant.org.
《太空科学秀》由Brilliant.org赞助播出。
Thanks to its watery history and potential for past life, Mars has been fascinating people for decades.
因为火星曾出现过水，又有承载水的可能，所以火星过去几十年来一直吸引着人类。
So it's no surprise that we've sent more spacecraft there than any other planet.
所以，我们向火星派送的航天器比其他行星要多，也就不足为奇了。
We're talking 45 missions. Most other worlds have had just a small handful.
我说的多可是指45次任务哦。很多其他星球也只接收过为数不多的几次任务。
The problem is, around half of the probes that have ever attempted to explore Mars have either crashed or disappeared.
问题在于，在发往火星的所有探测器中，近半数不是坠毁就是杳无音信了。
So as much as we want to understand the planet, getting to its surface is no easy feat.
虽然我们想要了解火星，但抵达火星表面并非易事。
Mars's unique atmosphere often gets the better of us, and it's taken some creative engineering to get to the ground.
火星独特的大气层让我们黔驴技穷，小有创造性的工程技术才能助我们抵达火星表面。
Before Mars, the only places we'd ever landed spacecraft were the Moon and Earth.
在火星之前，我们发送过航天器的地方只有月球和地球。
And while that did come with challenges, we had strategies nailed down pretty well for both.
虽然也遭遇过诸多挑战，但我们还是制定了切实可行的方案。
The hard thing about landing on Earth is that our thick atmosphere creates extreme friction and heat with incoming spacecraft.
着陆地球的难点在于：地球的大气层很厚，所以航天器在进入的时候，会产生极大的摩擦力和热量。
But we've solved that problem with heat shields, and besides, that thick atmosphere also means parachutes work very well.
但我们用防热罩解决了这个问题。而且大气层较厚也意味着降落伞会很管用。
The Moon is kind of the opposite. It has virtually no atmosphere, which gets rid of the heat problem, but it also means parachutes don't work.
月球则恰好相反。月球几乎没有大气层，所以就没有产生热量的问题了，但这也意味着降落伞不管用。
We have to use retro-rockets to land, little rockets that fire underneath a spacecraft to slow its descent.
我们需要反推进火箭来着陆。所谓反推进火箭，就是小型火箭，可以在航天器下方提供动能，为其下降过程减速。
Mars, meanwhile, is a whole different beast.
而且火星真的怪异。
It comes with all the challenges of landing on Earth and the Moon, but with none of the real benefits.
在地球和月球着陆的挑战，火星都有，但好处火星却一个都没占着。
Its atmosphere is 100 times thinner than Earth's, meaning parachutes can't grab onto enough air to completely slow down the spacecraft.
火星的大气层厚度是地球的1/100，也就是说：降落伞无法通过空气的作用来使航天器减速。
But unlike the Moon, there's also just enough atmosphere to create problems.
但跟月球的不同点在于：虽然火星大气层稀薄，但也足以引发许多问题。
Just like friction causes space rocks and old satellites to burn up in Earth's atmosphere, a space probe entering Mars's atmosphere can get hotter than 2000 degrees Celsius.
跟摩擦让太空岩石和陈年卫星在地球大气层中燃烧一样，进入火星大气层的空间探测器温度可高达2000摄氏度以上。
That's hot enough to melt iron, and just about every other metal.
这个温度足以融化钢铁等任何金属了。
So the millions of dollars' worth of machinery we send to Mars needs serious protection to keep from being fried.
所以，我们为了发送航天器到火星而在机器上投入的上百万元成本需要切实的防护才能不会烧焦。
So, how do you get an expensive, heavy chunk of metal, traveling tens of thousands of kilometers an hour, to come gently to a stop on the surface of another world?
所以，成本高昂、质量很大的金属，在高速行驶了很久之后，如何能在另一个行星的表面戛然而止呢？
A whole lot of creativity. And probably a good amount of coffee.
这需要进行重大创新，喝很多杯咖啡才能想到。
Every mission to land on Mars starts with something called an aeroshell: a special capsule that protects its cargo against the heat.
着陆火星的每个任务，其第一步，都是减速伞：一种特殊的胶囊，可以保护其承载物不受高温影响。
Its outer layer is filled with a material, called an ablator, that was invented in the 1970s for the first Mars landers: the Viking missions.
其外层填满了一种名为烧蚀体的材料。这种材料是上世纪70年代为火星着陆器发明的。那次任务是海盗号。
It reacts with the Martian atmosphere in a way that removes the heat and leaves behind a trail of gas.
这种材料会跟火星大气层发生反应，将热量消散，只留下气体。
It gets so hot that it glows red, but inside the capsule, cargo stays a little cooler than room temperature.
由于温度极高，会导致材料烧得通红，但胶囊内部的承载物温度会比室温低一些。
Next, once friction has slowed things to about 1600 kilometers per hour, a parachute opens, and part of the aeroshell is cast off.
接下来，一旦摩擦将速度降至1600千米/小时，降落伞就会张开，而减速伞的部分会自动脱落。
Amazingly, engineers are still using a parachute pretty similar to the one designed for the Viking landers more than 40 years ago.
令人惊奇的是，工程师们依然在用的一种降落伞跟海盗着陆器的降落伞十分相似，而海盗任务的降落伞是40多年前设计的。
It's made of nylon and polyester, with tethers made of the same material as bulletproof vests.
这种降落伞是用尼龙和聚酯做的。其拴绳的材质跟防弹衣相同。
That makes it super strong and light, which is really important, considering the craft is still moving at supersonic speeds when it deploys.
这种材质结实又轻薄，这一点很重要，因为航天器的速度是以超音速运动的。
And while it isn't enough to slow down a spacecraft all the way, it does help.
虽然不能确保航天器一直处于减速的状态，但聊胜于无。
After a few minutes, the parachute brings the craft down to a few hundred kilometers per hour, and it gets discarded along with the rest of the aeroshell.
几分钟的时间，降落伞就能将航天器减速到几百千米/小时，然后降落伞就跟减速伞的其他部分一起脱落了。
Now, this is where things get really creative, and no type of mission has been exactly the same.
接下来就是见证创新的时刻了——这是绝无仅有的一点。
Engineers have had to come up with special solutions to get each spacecraft on the ground.
工程师不得已，要想出特殊的解决方案来让航天器着陆。
For example, those 1970s Viking landers used retro-rockets like on the Moon.
比如，上世纪70年代的海带航天器用到了反推进火箭，跟着陆月球的航天器类似。
But there was always the possibility that they'd botch a landing on uneven ground.
但航天器还是有可能在不平坦的地面上勉强着陆。
And while they were fine for landers, carrying around a bunch of rockets would be a pointless burden on the rovers we started sending to Mars in the ‘90s.
虽然对航天器来说无伤大雅，但上世纪90年的背景下，携带许多火箭对于航天器来说是本没有必要的负担。
So for the Pathfinder mission that landed in 1997, which included the first experimental rover, engineers tried a new method: a cluster of airbags.
1997年着陆的开路者号包含了首个实验探测器。工程师尝试了一种新方法：组合安全气袋。
After slamming into the ground, this robotic explorer bounced along for hundreds of meters.
在快速着陆在地面上后，这个机器化的探测器弹起了数百米。
And by bounced, I mean it shot several stories into the air and moved as fast as cars on the freeway before rolling to a stop.
我所说的“弹”是指向空中弹起了几层楼那么高，速度就像高速公路上行驶的车那样快，最后滚动到停止。
But somehow, it worked. In fact, it worked so well that scientists used the same system to land the more recent Spirit and Opportunity rovers.
不过，不管怎么说，竟然有用。实际上，效果出奇的好，所以科学家用同样的系统来着陆最近的勇气号和机会号火星探测器。
Then, in 2012, things had to change again, because airbags were out of the question for the Curiosity rover.
随后，也就是2012年，情况再次发生了变化，因为气袋根本无法用在好奇号探测器上。
It was nearly five times the mass of Spirit and Opportunity, so engineers came up with their most epic solution yet.
因为好奇号的重量是勇气号和机会号的近5倍，所以科学家想到了目前为止最特别的解决方案——
They called it a sky crane. Basically, it was a stage that used retro-rockets to hover above the surface.
也就是“空中吊车”。基本而言，这里会用反推进火箭在火星表面盘旋。
From there, it slowly lowered the rover on a tether, then cut itself free and flew off to crash-land nearby.
在这里，它会缓慢地将探测器下降至拴绳上，然后它会自我挣脱，飞到附近被撞击过的地面。
NASA's next Mars mission, Mars 2020, will use a similar strategy.
美国宇航局的下一次火箭任务，也就是火星2020，也会用到相似的战略。
But who knows what kind of unique designs we'll see after that.
但谁知道在这之后会不会有其他独特的设计呢。
Oh, and in case this all isn't complicated enough, every single step of these landings also has to happen completely automatically.
为了避免复杂，着陆过程的每一步都是全自动的。
That's because radio signals travel at the speed of light, so they take at least eight minutes to go from Earth to Mars and back, which is longer than it takes to land.
这是因为无线电讯号会以光速行使，所以在地球和火星之间往返至少需要8分钟，这比它着陆的时间还要长。
And it's not exactly easy to put a spacecraft on autopilot in a world that's still really foreign and unpredictable.
要将航天器放在火星的自动驾驶仪上，这难度很大，因为火星不是地球，可预测性很低。
The good news is, all these years of work have been well worth it.
好消息是这些年的工作都值了。
Besides preparing us for future exploration, these landers have brought us closer to knowing what Mars was like in the past.
除了为未来的探索做准备之外，这些着陆器让我们进一步了解了火星过去的样子。
That could help us figure out whether or not it ever hosted life, and what it would take to support human life one day in the future.
这可以帮助我们了解火星上是否曾经孕育过生命，以及如果未来人类要在火星生活，需要什么支持条件。
And it's all thanks to some brilliant engineers and organizations.
这都要感谢超赞的工程师和各机构。
If you've ever dreamed of becoming an engineer who lands spacecraft on other planets, you'll want to make sure you're an expert on orbital mechanics.
如果大家也曾梦想过成为一名工程师，并在其他星球着陆航天器的话，先要精通轨道力学哦。
And conveniently, Brilliant has some courses that can really help you out.
为了方便大家学习，Brilliant也推出了一些课程。
Once you've learned how orbits work, you can even try their quiz about how to send a spacecraft to Mars.
一旦大家了解了轨道运行的原理，就可以尝试去做如何发射航天器到火星的测试了。
I like how Brilliant makes the physics easy to understand, and their visuals and diagrams are super helpful.
Brilliant让物理学简单易懂，这一点我很喜欢。而且Brilliant的可视教具和图形都很有用。
You can check it out at Brilliant.org/SciShowSpace, and right now, the first 200 people to sign up at the link will get 20% off of an annual premium subscription to Brilliant.
详见Brilliant.org/SciShowSpace。目前，前200名在该链接注册的用户可以得到20%的年费减免。
