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土星上有什么?“卡西尼”飞船的六大奇特发现

2017-12-25ByJesseEmspak

新东方英语·中学版 2017年12期
关键词:卡西尼泰坦土星

By+Jesse+Emspak

1997年,美國宇航局发射“卡西尼”号宇宙飞船,经过七年的飞行,“卡西尼”号到达了预定轨道,开始围绕土星旋转。此后13年间,“卡西尼”源源不断地发回许多关于土星的震撼人心的美图,让人们对宇宙的认识更进一步。然而就在2017年9月15日,“卡西尼”燃料即将耗尽,不得不走向生命尽头,按照预设坠毁在土星大气层。尽管它已经不在了,但它将因带来宝贵的资料而被历史永远铭记。

The first Saturn-dedicated spacecraft, Cassini, orbited the planet for about 13 years. The craft's fiery2) (and lethal3)) plunge through the planet's atmosphere on Friday, Sept. 15, 2017, may be the end for the mighty spacecraft. But its discoveries about the ringed planet4) will live on, at least here on Earth.

Some of those findings were more than enlightening—they were downright5) odd. Here's a look at the weirder side of the Cassini mission.

Hyperion6) Is Static7).

Saturn's moon Hyperion is an irregularly shaped rock that orbits Saturn some 1.48 million km above the planet's cloud tops. In one of Cassini's flybys in 2005, the probe found itself in a beam of charged particles emanating8) from that moon. It turned out that Hyperion was charged with static electricity, so much so that Cassini could detect the charge, according to NASA.

Static electricity is an important phenomenon on Earth's moon, due to the combination of dryness (there's no water) and exposure to charged particles from the sun. Cassini's detection of Hyperion's "particle beam" was the first time the phenomenon had been seen on a moon of another planet in our solar system. And it offered insights9) into how scientists could design spacecraft to survive in harsh, electrically charged, environments in the future, researchers said.

Birth of a Moon

Saturn has 62 moons, from giants like Titan, which is larger than the planet Mercury, to 400-meter-wide moonlets. But how often do you see a moon being born? Cassini might have caught such an event in 2014. NASA released images of the edge of Saturn's A ring10) , one of the bright and wide outer regions. Cassini got pictures of an arc that was 20 percent brighter than its surroundings, about 1,200 km long and 10 km wide.

The mission scientists also saw what looked like unusual irregularities11) on the edge of the ring: small bulges12) caused by the gravitational pull of something nearby. The arc and protuberances13) on the ring could have been a small moon accreting14) from bits of icy material, a replay of the birth process of Saturn's larger moons, researchers said. NASA said there was no expectation that the object, which they named Peggy, would get bigger—it's less than a mile across—and it may even fall apart. But seeing it illuminates much of the process of moon-building, scientists said.

“卡西尼”号是第一艘专门探测土星的宇宙飞船,它绕着土星转了大概有13年。在2017年9月15日星期五,“卡西尼”坠入了土星的大气层,其焚毁或许是这艘了不起的宇宙飞船生命的结束。但它有关土星这个带有行星环的行星的发现会继续留存,至少在我们地球这里会这样。

“卡西尼”号的一些发现可绝不只是具有启发性,而是非常的怪异。下面就让我们来看看“卡西尼”土星探测任务中那些更为奇特的发现吧。

土卫七带静电

土星的卫星土卫七是块形状不规则的岩石星体,在距离土星云层上方大约148万公里的轨道上环绕土星运行。“卡西尼”号曾多次路过土卫七,在2005年的一次擦肩而过中,“卡西尼”号探测到自己处在由土卫七放射出的带电粒子束中。原来,土卫七带有静电,而且电量还不小,竟能让“卡西尼”号检测到,美国宇航局如是说。

静电现象是地球的卫星月球上的一个重要现象,这是由于月球环境干燥(那里没有水)且暴露在来自太阳的带电粒子中而形成的。“卡西尼”号探测到了土卫七上的“带电粒子束”,这是我们首次在太阳系内另一颗行星的卫星上发现这种现象。研究人员说,这让科学家们深刻地认识到将来应如何设计宇宙飞船,以便使其能经受得起严酷的带电环境。

卫星的形成

土星有62个卫星,既有类似土卫六泰坦星(它比水星还大)这样的大家伙,还有不少直径400米的小卫星。但是你多久才有机会看到一次卫星的形成呢?也许2014年“卡西尼”号就捕捉到了这一幕,当时美国宇航局发布了一组土星A环边缘的照片。A环是土星环外层其中一个明亮、宽阔的环。“卡西尼”号拍摄到了一段亮度比周围环境高出20%的弧形的照片,这段弧形约有1200公里长,10公里宽。

参与该探测任务的科学家们还在A环边缘发现了一些看起来非同寻常的不规则体——那是在周围什么物体的引力拖拽作用下形成的许多小突起。研究人员说,该环上的这段弧形和那些突起有可能是由冰物质碎片依附累积而形成的一个小卫星,这再现了土星的那些更大卫星的形成过程。美国宇航局的工作人员说,预计这个被他们命名为“佩吉”的星体并不会增大(它的直径不超过1英里),甚至还可能会瓦解。不过科学家们说,看到它让人们了解了卫星形成过程的许多过程。

1. methane [?mi?θe?n] n. 甲烷;沼气

2. fiery [?fa??ri] adj. 熊熊燃烧的

3. lethal [?li?θl] adj. 致命的

4. ringed planet: 带有行星环的行星,这里指土星。

5. downright [?da?nra?t] adv. (强调令人不快或负面的事或行为)彻头彻尾地,十足地,完全地

6. hyperion: 土卫七

7. static [?st?t?k] adj. 带有静电,发射的

8. emanate [?em?ne?t] vi. 散发,发射

9. insight [??nsa?t] n. 洞悉;深入了解;深刻见解

10. Saturn's A ring: 土星的行星环十分宽阔,结构复杂,很像密纹唱片上那一圈圈的螺旋纹路。科学家把土星环分为了几个部分,其中最明亮、最宽阔的是A环和B环(A环位于外层)。光环的各部分之间有明显的裂缝,最大的裂缝是A环和B环间的裂缝,这一裂缝是由天文学家乔万尼·卡西尼(Giovanni Cassini)于1657年发现的。

11. irregularity [??reɡj??l?r?ti] n. 不规则

12. bulge [b?ld?] n. 突起;疙瘩

13. protuberance [pr??tju?b?r?ns] n. 突起物

14. accrete [?'kri:t] vi. 共生,依附

土星A環上的小凸起

土星环分区

Discovery

探索之旅

Hexagonal18) Jet Stream

Perhaps one of the weirdest things about Saturn is the planet's hexagon. It looks almost artificial—a set of jet streams around Saturn's north pole that takes on the shape of a hexagon and is unlike anything on Earth.

The hexagon is about 32,000 km wide and reaches some 100 km into the planet's atmosphere. Planetary scientists have tried various models to explain how one might get such a neat geometric shape.

There are several proposed explanations for the hexagon. In 2015, Raúl Morales-Juberías at the New Mexico Institute of Mining and Technology led a team that ran computer simulations of Saturn's atmosphere. The researchers found that a jet stream moving around Saturn's pole at more than 320 km/h will eventually meander19) into a hexagonalshape, suggesting such a jet stream is the culprit20).

Titan Has Water, Too—It's Just Really Salty

Titan gets a lot of press for its methane lakes and hydrocarbon15) snow. But it's also an ocean world of sorts16): Cassini data showed that Titan has a very salty subsurface ocean filled with water not unlike17) that in the Dead Sea on Earth.

泰坦星构造图

泰坦星上也有水,

但真的很咸

土卫六泰坦星因为其上有许多甲烷湖和碳氢化合物的雪而被媒体大量报道,但它也勉强称得上是个海洋的世界。“卡西尼”号探测到的数据表明,泰坦星上有含盐量很高的地下海,里边的水和地球死海里的水虽说不一样,但也很类似。

六边形风暴

也许土星上最不可思议的景象之一就是它的六边形风暴,看起来简直是人造的一般——一组大气急流围绕着土星北极流动,形状呈六边形,全然不同于地球上的任何情形。

这个六边形风暴大约有3.2万公里宽,深入土星大气层约100公里左右的地方。行星科学家们业已尝试建立了各种各样的模型,想要解释如此巧妙的几何形状是如何才能产生的。

人们提出了一些假设来解释六边形产生的原因。2015年新墨西哥矿业及科技学院的劳尔·莫拉莱斯·朱伯瑞斯带领一个团队用计算机模拟了土星大气层。他们研究发现,土星北极周围以大于320公里的时速流动的大气急流最终蜿蜒形成六边形的风暴,这表明这样的急流本身才是始作俑者。

土卫六泰坦星

15. hydrocarbon [?ha?dr??kɑ?b?n] n. 碳氢化合物

16. of sorts: 算是;勉强称得上

17. not unlike: 相似的,用于表达A与B有其相似之处,但本质上是不同的。

18. hexagonal [heks??ɡ?nl] adj. 六角形的;六边形的

19. meander [mi??nd?(r)] vi. (河流、道路)蜿蜒而行,迂回曲折

20. culprit [?k?lpr?t] n. 引起问题(或不利情势)的事物

21. Voyager: “旅行者”号,共有“旅行者”1号、“旅行者”2号两个,是美国于1977年相继发射的两个宇宙飞船,用于探索外太空。两者都曾从土星附近飞过,发回关于土星的一些数据。

22. drizzle [?dr?zl] n. 毛毛雨

23. bounty [?ba?nti] n. 大量提供的东西;慷慨的赠予

Lightning on Another Planet

On Aug. 17, 2009, Cassini made the first movie of lightning on Saturn. This was the first time the phenomenon had ever been captured in video on another planet. Andrew Ingersoll, a Cassini imaging science subsystem team member at the California Institute of Technology, noted in a press release that the storms that make the lightning are at least as powerful on Saturn as they are on Earth, though they happen less often on the ringed planet.

Unlike Earthly thunderstorms, though, Saturnian lightning storms can last months rather than hours, Ingersoll said. The initial images of lightning were taken at night, but two years later, Cassini caught images of lightning on Saturn's dayside.

Titan's Weird Weather

In the early days of Cassini's mission, in 2006, the Huygens probe aboard the Cassini craft found evidence of methane drizzles on Titan. At the time, little was known about Titan's surface; we knew from Voyager21) data only that the atmosphere was about 1.5 times the pressure of Earth's and was made largely of nitrogen with a small amount of methane and hydrogen.

Cassini gave us the first direct look at the methane lakes at the moon's poles. Huygens beamed back a picture of the weather at the surface and found that the weather forecast on Titan was pretty straightforward: a 100-percent chance of methane drizzles22) every day and temperatures of about minus 184 degrees Celsius.

"Cassini may be gone, but its scientific bounty23) will keep us occupied for many years," said Linda Spilker, a Cassini project scientist. “We've only scratched the surface of what we can learn from the mountain of data it has sent back over its lifetime."

“或許‘卡西尼号已经消失了,但它带来的大量科学馈赠将会让我们埋头研究好几年,”“卡西尼”号项目的一位科学家琳达·斯皮尔克说道,“从‘卡西尼号毕生传来的海量数据中,我们可以获得许多,现在我们只不过刚了解到一些皮毛罢了。”

另一个行星上的闪电

2009年8月17日,“卡西尼”号首次拍摄到了土星上的闪电视频。这是该现象首次在另一行星上被以视频的形式拍摄到。来自加州理工学院的安德鲁·英格索尔是“卡西尼”成像科学子系统工作组的成员,他在一次新闻发布会中指出,引发土星闪电的暴风雨强度至少和地球上的差不多,尽管闪电在土星这个带有行星环的星球上发生得没那么频繁。

不过,和地球上的雷雨不同,土星上电闪雷鸣的暴风雨可以持续数月,而不是几小时,英格索尔说。“卡西尼”号第一次是在晚上拍摄到闪电图像的,但是两年之后它在白天也抓拍到了土星的闪电图像。

泰坦星上的怪天气

2006年“卡西尼”任务刚开始进行的那段日子,“卡西尼”号飞船携带的“惠更斯”探测器就发现了证据,表明泰坦星上下着甲烷毛毛雨。当时我们对泰坦星的表面知之甚少,仅从“旅行者”号飞船的数据中得知,泰坦星的大气压约是地球气压的1.5倍,主要是由氮气组成,有少量的甲烷和氢气。

“卡西尼”号让我们第一回直观地看到位于泰坦星两极上的甲烷湖。“惠更斯”探测器发回一张泰坦星地表天气情况的照片,发现那里的天气预报要简单直接得多——那里每天百分之百会下甲烷毛毛雨,气温大约是零下184℃。

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