揭開水星核心之謎（圖）
05-28
揭開水星核心之謎（圖）
科學家們利用了一項技術，該技術有點象測量從迪斯科舞會球形燈上射出光影。他們發現：水星核心至少呈部分熔化狀態。
水星的金屬性核心從中心部位延伸到水星大部分半徑的位置。儘管雷達觀測顯示其核心至少呈部分熔化狀態，但科學家們不能確定水星核心為何在幾十億年的時間裡沒有凝固。
Mercury"s core secrets exposed
| Tiny Mercury, the innermost planet in the solar system, appears to have a partially liquid core. | 太陽系最裡面的微型行星——水星好象有著半液態的核心。 |
| That new finding may help explain the planet"s weak magnetic field, even as it opens more puzzling questions about how the core has maintained a semi-liquid state for billions of years. | 這個新發現可能有助於解釋水星的弱磁場。可是，幾十億年來水星核心是如何保持半液體狀態的？對於這個情況，該發現引出了更多的疑難問題。 |
| Because of its small size - Mercury is 40% smaller than Earth - the laws of physics suggest that its core should have cooled and solidified long ago. But an innovative radar technique that measured Mercury"s rate of rotation shows distinctive signs that the planet consists of both solid and semi-liquid matter. | 水星比地球小40％。由於水星體積小，根據物理法則，其核心本應該在很久以前就已經冷卻並且凝固起來。然而，利用一項測量水星自轉速度的雷達創新技術，所測得的獨特信號顯示，水星的組成成分中既有固態物質，也有半液態物質。 |
| "What we"ve been able to do from the ground is to detect tiny changes in the spin rate of Mercury that indicates the planet has a molten core," says astronomer Jean-Luc Margot, an assistant professor at Cornell University. "The molten core tells us something very important about the planet"s body temperature. A planet the size of Mercury should have cooled off by now. It should have radiated all its heat," he says. | 「我們在地面上所能夠做的就是：探測水星自轉速度的細微變化，這種細微變化說明水星擁有一個熔化的核心，」天文學家、康奈爾大學助理教授吉恩-盧克·馬戈特說。他指出：「有關水星的表面溫度問題，這個熔化的核心向我們說明了極其重要的情況。到現在為止，象水星大小的行星本應該已經散發出所有的熱量而冷卻下來。」 |
| The finding, published today in the journal Science, helps to explain the weak magnetic field the Mariner 10 probe detected during fly-bys in the mid-1970s. | 該發現發表在今天出版的《科學》雜誌上。20世紀70年代中葉，「水手」10號探測器飛臨水星的時候發現水星的磁場很弱，目前的發現有助於解釋這個情況。 |
| One way for a planet to generate a magnetic field is to have a core of liquid or semi-liquid metal, like Earth"s. But the discovery also raises the question of what factors are keeping Mercury"s interior hot enough to remain molten. | 能夠使行星產生磁場的一種情形是：跟地球一樣，擁有液態或半液態金屬核心。但是，該發現也提出了如下問題：哪些因素在保持著水星內部的熱度，足以使其核心保持熔化狀態？ |
| One possibility is that heat-trapping lighter elements, such as sulfur, are doing the trick. But scientists are stumped as to how those elements could condense in a place so close to the Sun. "The people doing thermal evalution calculations are certainly scratching their heads figuring out what you need to explain a molten core in such a small planet," Margot says. | 一種可能性就是善於捕捉熱量易燃元素（如：硫磺）在作怪。但是，這些元素為何可以聚集在離太陽如此近的地方，科學家們對此感到困惑。「進行熱量評估計算的研究人員肯定會感到迷惑不解，他們會考慮：該拿什麼來解釋如此小型行星中的熔化核心呢？」馬戈特說。 |
| More answers may come when NASA"s Messenger spacecraft arrives at Mercury. The probe is expected to make three fly-bys before settling into orbit for long-term studies in 2011. The first pass will come in January. Scientists were awaiting Messenger"s arrival to resolve, among other questions, the mystery of the planet"s core. | 美國航空航天管理局的「信使」號太空船到達水星後，也許會進一步找到答案。預計該探測器將飛臨水星3次，然後於2011年進入軌道，以實施長期研究任務。一月份，「信使」號太空船將首次經過水星。科學家們在等待「信使」號的到達，以便解決問題，尤其是水星核心之謎的問題。 |
| But Margot and his colleagues beat them to it using pairs of radio telescopes in California, West Virginia and Puerto Rico to bounce radar signals off Mercury and measure the reflected signals on Earth. | 然而馬戈特及同事捷足先登，他們利用加利福尼亞、西弗吉尼亞和波多黎各的射電望遠鏡發回水星的雷達信號，然後在地球上測量水星的反射信號。 |
| Margot likens the technique to watching the patterns of light on a wall cast by a circling disco ball. By knowing the exact distance between two set points on the wall, for example, subtle variations in the ball"s spin rate can be measured. | 馬戈特把這個技術比作是：觀看迪斯科舞廳里旋轉的球形燈投射在牆壁上的燈光圖案。例如，了解到牆壁上兩個定點之間的確切距離，球形燈旋轉速度的細微變化就可以測量了。 |
| The team made more than 20 observations of Mercury between 2002 and 2006. | 在2002年到2006年之間，該研究小組對水星進行了20 多次觀測。 |
| "The technique was not fully appreciated ... until a few years ago," Margot says. "At that point I started looking into it and saw that it had potential. We could have done years ago." | 「這項技術直到幾年前才被充分重視起來，」馬戈特說，「那時我開始研究該技術，結果發現它擁有潛在的利用價值。我們本來在幾年前就可以拿下這項任務的。」 |
推薦閱讀：