Why is NASA sending a spacecraft to a metal world? - Linda T. Elkins-Tanton

譯者: Chen Chi-An 審譯者: Helen Chang

Somewhere between the orbits of Mars and Jupiter,

在火星和木星的軌道之間，

about 500 million kilometers away from Earth,

距離地球約五億公里處，

floats a metallic orb the size of Massachusetts.

漂浮著一個大小如 麻薩諸塞州的金屬球體。

That’s no moon...it’s 16 Psyche,

那不是衛星，而是「靈神星」，

one of the most massive asteroids in the solar system.

是太陽系中最大的小行星之一，

And it is the asteroid our droids are looking for.

也是機器人正在尋找的小行星。

We humans have managed to send robotic spacecraft

人類已將無人太空船

to all sorts of environments in space –

成功送至各種太空環境──

the gas clouds of Saturn and Jupiter,

土星和木星的氣體雲、

the icy wastes of Europa,

木衛二的冰凍環境、

and the rocky dunes of Mars.

火星的岩石沙丘。

But Psyche’s surface isn’t just hard rock –

但是靈神星的表面不只是硬岩石，

it’s heavy metal.

而是重金屬。

The asteroid mostly consists of nickel and iron,

該小行星的主要成分 為「鎳」和「鐵」，

by far the largest known body with such a composition.

是至今已知的、具有 類似成分結構的最大天體，

But we don’t yet know what it looks like;

但我們還不知道它長怎樣；

our best current radar images show a pixelated smudge.

目前最先進雷達只能看到 像素化的模糊圖像。

That’ll change in 2026,

但是到 2026 年就會不一樣，

when an unmanned spacecraft sent as part of NASA’s Discovery Program

因為「美國太空總署發現計劃」 所發送的無人太空船

is scheduled to arrive.

預計將在 2026 年抵達。

為何美國太空總署 對靈神星如此有興趣？

So why is NASA so interested in Psyche?

Are we going to mine all that metal, or build a giant space magnet?

要開採金屬，還是 要建個巨大的太空磁鐵？

Actually, the real reason is right under our feet.

其實，真正的原因就在我們腳下。

The core of the Earth is thought to consist of a solid nickel-iron center

地心被認為含有固態的鎳鐵內層

with a molten outer layer.

和熔融的外層。

But we’re prevented from studying it up close by 2,800 kilometers of solid rock.

而其更外圍 2800 公里的 固態岩石讓我們無法研究地心。

The deepest we’ve been able to drill is 12 kilometers.

我們最深只能鑽到十二公里。

Even if we could go further,

就算能鑽更深，

the pressure at the core is three million times higher than at the surface,

地心的壓力是地表的三百萬倍，

with a temperature of 5,000 degrees Celsius.

溫度高達攝氏五千度。

Simply put, a journey to the center of the Earth is out of the question for now.

簡單來說，深入地心的 探索之旅目前是不可能的，

So scientists have had to resort to indirect ways of studying the core,

所以科學家必須用 間接方法來研究地核，

like measuring earthquake waves that pass through it,

如測量通過地心的地震波，

or studying minerals thought to have formed there.

或研究可能在地心形成的礦產。

But what if the best way to study Earth’s inner space

但如果研究地球內部最好的方法是

is by visiting outer space?

拜訪外太空呢？

After all, we have a pretty good idea of how our planets formed.

畢竟，我們清楚知道 行星是如何形成的，

Dust and gas orbiting our young Sun cooled and collided

太陽系初期，繞著太陽的 塵埃和氣體冷卻並碰撞，

to form a few thousand miniature bodies we call planetesimals.

形成數千個小型天體， 被稱為「微行星」。

As these continued to orbit, some combined to grow larger,

微行星繼續繞太陽公轉， 一些結合在一起變得更大，

eventually forming our planets.

最終形成了行星；

Others experienced impacts that broke them apart into smaller chunks–

其他的微行星碰撞而碎成了小塊，

the asteroids we see today in the belt between Mars and Jupiter.

就是現在火星和木星之間 看到的小行星帶。

What makes Psyche so special

讓靈神星如此特別的是，

is that it appears to have been a planetesimal

顯然在從微行星轉變成行星的過程，

well on its way to becoming a planet,

with a rocky exterior surrounding a metal core.

其核心是金屬而外表是岩石。

But its progress was cut short by a series of hit-and-run collisions

但是一系列的碰撞中斷了它的轉變，

with other planetesimals

在與其他微行星碰撞後，

that knocked off the rocky crust until only the core remained.

靈神星表面的岩石被撞碎， 僅剩金屬核心。

經歷多次破壞性的碰撞

Experiencing that many destructive collisions

with no additive ones in between is statistically very unlikely,

而沒添加新岩石的機會微乎其微，

making Psyche an amazingly rare opportunity

因此，靈神星成為一個罕見例子，

to study an exposed metallic core.

暴露在外的金屬核心能被研究。

To do that, NASA’s robotic orbiter will be equipped

為此，美國太空總署的機器人衛星

將裝載一系列的精密儀器。

with an array of advanced instruments.

A spectrometer will analyze the gamma rays and neutrons

「光譜儀」會分析宇宙射線撞擊靈神星

produced when Psyche is struck by cosmic rays.

所產生的伽馬射線和中子。

Each element in the periodic table

元素週期表的每種元素

releases gamma rays of specific wavelengths,

都會釋放特定波長的伽馬射線，

so these measurements will tell us what elements are found on the surface.

因此這些數據會告訴我們 其表面的元素。

A magnetometer will measure Psyche’s magnetic field,

而「磁力儀」會測量靈神星的磁場，

allowing us to learn more

讓我們更了解

about how Earth’s magnetic field is generated at its core.

地核如何產生地球的磁場。

And of course, an imager will give us a closer look at the surface

當然，「成像儀」讓我們能比之前 更清楚看到靈神星的表面，

than ever before.

Visiting a whole new kind of world is exciting enough on its own.

進入一個全新世界 本身就是件令人興奮之事。

But the mission to Psyche gives us a unique chance

而靈神星任務給了我們特別的機會

to discover our own planet’s innermost secrets in an orbit far, far away.

能從遙遠的軌道 發現地球最深處的秘密。