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2014年12月1日 星期一

New from Scientific American,科學人又來了,perchlorates這個字你懂算你厲害!Learn something new every day! 本周答案揭曉!



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Scientific American這個單元也可以下載至Podcast喔,大家可以多利用,用手機也聽。
Martian Soil Salts May Make Water Ice All Wet

Within a Mars-like laboratory environment, perchlorate salts known to exist on Mars were able to lower the freezing point enough to get ice to turn to liquid water.

Clara Moskowitz reports 
  
If Martians exist, even the microbial 微生物/細菌sort, they probably need liquid water. Temperatures on the surface of the Red Planet 火星are below freezing零度以下, but signs exist that water flowed in the past—and perhaps still does, thanks to a Martian version of antifreeze防凍劑.

Salts lower the freezing point of water, as anyone knows who has thrown salt on
an icy sidewalk結了冰的走道. And both NASA’s Phoenix and Curiosity美國國家航空暨太空總署的鳳凰號與好奇號missions found salts called perchlorates高氯酸鹽sprinkled around the Martian surface.

To see how perchlorates might act on Mars, researchers re-created the pressure, humidity and temperature of the planet inside a
metal cylinder金屬的圓柱狀物. They put a thin layer of perchlorates on top of water ice inside the chamber空間. Within minutes, droplets of liquid滴狀的液態物 water formed, even at minus 100 degrees Fahrenheit華氏零下一百度.

Some scientists thought perchlorates might
condense water vapor凝結大氣中的水蒸氣 from the atmosphere. But within the cylinder, no liquid water formed in the presence of salts, either alone or on Mars-like soil, unless ice was present, too. The study is in the journal Geophysical Research Letters.

地球物理研究通訊GRL)是美國地球物理出版的期刊。該期刊出版以物理、化學、生物學等學科研究地球、太陽和太陽系的論文。地球物理研究通訊只刊登短篇研究快報,文章長度一般是 3 5 頁,主要集中在特定學科或廣泛應用在地球物理學界的論文。
The finding study could explain mysterious globules小水珠 seen on the leg of the Phoenix in 2008. The lander降落者 may have been dotted with佈滿 drops of otherworldly此指來自另外一個世界的 water.

2 則留言:

  1. 老師,這篇反覆看又聽了好多次,對於"But within the cylinder, no liquid water formed in the presence of salts, either alone or on Mars-like soil, unless ice was present, too."不太理解 意思是科學家懷疑滴狀的水是來自空氣,但金屬圓柱裡如果沒有冰,就不會產生任何水這樣嗎?(覺得好困惑)

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  2. Hi ruoshen,

    短篇的SC容易有表達不清楚的地方。如果你有興趣可以參考這個網址
    http://ns.umich.edu/new/multimedia/videos/22274-martian-salts-must-touch-ice-to-make-liquid-water-study-shows (這是密西根大學做的實驗)

    這篇主要在說明科學家在一個圓柱體內做測試,這測試包含了兩個狀況
    一個是只有perchlorate但是沒有冰的環境(這就是文中說的alone),一個則是把perchlorate放在冰上(因為火星很冷,所以土壤上可能會呈現結冰狀態)

    They tested two scenarios: perchlorate by itself and perchlorate on top of water ice.
    In the perchlorate-only experiments, they put millimeter-thick layers of salt on a temperature-controlled plate or Mars-like soil. Even after more than three hours, no liquid water formed.放在類似火星土壤上面percholrate沒有出現水

    When the researchers placed perchlorate directly on a 3-millimeter-thick ice layer, drops of liquid water formed within minutes when the chambers reached -100 F. That's well within the range of conditions observed at the Phoenix landing site.但是將perchlorate放在冰上,即便是華氏零下100度也能形成小水珠。

    這整篇在說明火星上存在的perchlorate有可能會讓冰化成小水珠。所以你的理解方向性正確。科學家一直試圖在火星上找水,之前也有研究顯示火星上或許真的存在過水。但是火星非常寒冷,如何讓冰融化變成水是一個問題。所以perchlorate可能是一個線索。測試顯示只要把perchlorate放在冰上面,即便是零下的狀態也足以讓冰釋放出水汽與小水珠(但是不足以融化冰讓冰變成水的程度)所以Phoenix探測號跑到火星上,後來支架有出現小水珠(這水是打哪來?科學家很好奇),這可能意味著火星酷冷的環境,可能因為perchlorate的關係,有可能還是能出現小水滴。水滴可能來自於冷空氣中的水氣,這些水汽是因為perchlorate而融化成小水珠。目前也只有小水珠而已。

    這樣解釋有比較清楚嗎?

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