Land an unmanned spacecraft on Titan, Saturn's largest moon, and explore the surface for evidence of potential alien life.

這任務就是讓一架無人的太空飛行器降落至泰坦 —— 土星最大的一顆月亮 (衛星)，並且探索星球表層、找尋潛在的外星生物證據。

The billion-dollar mission will test NASA engineers like never before, because if you're going to explore Titan, there's something you need to know.

這項耗資十億美金的任務將帶給 NASA 的工程師前所未有的挑戰，因為說到探索泰坦，有一些事情你要先知道。

Just like our own moon, Titan orbits a planet, but it actually looks and behaves more like an Earth.

就和地球的月亮一樣，泰坦也繞著一顆星球運行，但它的外觀和運作方式其實比較像地球。

And that's why, for this mission, NASA opted for a different kind of spacecraft.

這也是為什麼 NASA 為這次任務選擇了一種完全不同的飛行器。

This is Dragonfly.

見見「蜻蜓」。

It's a nuclear-powered drone that's the size of a large lawn mower.

它是一台核能驅動的無人機，大小等同於一台大型除草機。

Now if NASA is going to send a space drone anywhere, it's Titan, because, similar to Earth, it has a thick atmosphere, which can keep the drone aloft.

如果 NASA 要選一個地方將太空無人機送去，那肯定是選泰坦，因為它和地球一樣有一層厚厚的大氣層，能夠讓無人機停在空中。

Dragonfly is built like a helicopter, able to take short flights in between landings.

「蜻蜓」的結構和直升機類似，能夠在起飛和降落之間短暫飛行。

It will run on what's called a radioisotope thermoelectric generator, or RTG.

它的運作仰賴於放射性同位素熱電機，或稱為 RTG。

The RTG runs on radioactive decay from a reserve of plutonium-238, which not only will power the spacecraft for months on end, but will also keep it warm.

RTG 利用儲存槽中的鈽 -238 放射性衰變獲得能量，不僅可以替飛行器供電數月，還可以恆溫。

You see, the average temperature on Titan is minus 179 degrees Celsius, cold enough to freeze Dragonfly's circuits.

泰坦上的平均溫度可只有攝氏 -179 度，如此低溫足以凍結「蜻蜓」的電路。

But a byproduct of radioactive decay is heat, which will protect the fragile electronics on board, which Dragonfly will be using to study surface composition, temperature, weather patterns, and geological activity, as well as look for water, carbon compounds, and other signs of potential life.

好在放射性衰變的副產品就是熱能，可以保護電路板上脆弱的零件，「蜻蜓」要有這些電路才能分析地表組成、溫度、氣候形態和地質活動，同時尋找水、碳成分以及其他潛在生命的指標。

And NASA already has a good idea of where to explore.

而 NASA 早已經想好要探索哪裡了。

Back in the 2000s, NASA's Cassini spacecraft mapped entire sections of Titan's surface, uncovering lakes of liquid methane and possible ice volcanoes.

早在 2000 年初期，NASA 的卡西尼飛行器繪製了泰坦地表的地圖，發現了液態甲烷湖以及潛在的冰火山。

The ice volcanoes are of special interest, because scientists think they could launch underground water to Titan's surface.

這些冰火山尤其引人注目，因為科學家認為他們可以將地下水引至泰坦地表。

In fact, there's evidence to suggest that Titan has a vast subterranean ocean of liquid water about 80 kilometers down.

事實上有證據顯示 —— 在泰坦地下約 80 公里處有廣大的地下海洋，富含豐富的水。

And if that water is mixed with methane-based molecules lurking in Titan's surface lakes, there's a chance for life to form, according to some experts.

據某些專家所言，如果那些水和泰坦表層湖泊中的甲烷分子混合，就有可能形成生命。

And Dragonfly will have plenty of time to test that notion.

「蜻蜓」有許多時間能測試這個想法。

If all goes according to plan, Dragonfly will study Titan's surface for at least 2 1/2 years and is expected to travel over 175 kilometers.

如果一切按照計劃，「蜻蜓」將會有至少兩年半的時間可以研究泰坦地表，預估會行經超過 175 公里。

That's almost double the distance covered by all the Mars rovers combined.

那幾乎是所有火星好奇號行經距離加起來的兩倍。

And whether it finds alien life or not, there's plenty more science to discover.

無論它會不會找到外星生命，還是有許多科學知識有待探索。

For instance, Titan looks a lot like how scientists think Earth looked at a young age.

舉個例子，泰坦看起來類似於科學家猜想的地球早年外貌。

So, understanding Titan may help us uncover secrets of our own planet.

所以，了解泰坦或許能幫助我們揭開我們這顆星球的秘密。

What might we learn?

我們會學到什麼呢？

Well, there's only one way to find out.

只有一個方法能知道。

NASA plans to launch the spacecraft in 2026, when it will begin its eight-year journey through the solar system towards Titan.

NASA 預計在 2026 年發射飛行器，屆時它將開始為期八年的旅程，穿越太陽系前往泰坦。

So mark your calendars for 2034.

所以先記好 2034 這一年吧！