If life exists elsewhere in our solar system, Mars is the likeliest location, say most planetary scientists. There's just one problem: The Red Planet may never have been warm enough to support the wet biosystems that grace Earth. But that doesn't mean water didn't flow there. New findings suggest that martian water contained so much salt that it served as antifreeze.  

 許多行星科學(xué)家們表示，如果說生命存在于我們太陽系的其他地方，那么火星是它們最有可能生存的地方。問題只有一個：這顆紅色行星可能一直不夠溫暖，無法養(yǎng)育象地球上這樣濕潤的生物系統(tǒng)。但是，這并不意味著那里過去沒有流淌的水。新發(fā)現(xiàn)表明，火星水曾經(jīng)含有大量起著防凍劑作用的鹽分。

 The antifreeze idea comes from an analysis of martian rocks and mineral deposits. A team of scientists from NASA and two Spanish institutions poured over data collected by the rovers Spirit and Opportunity, along with the earlier landers Viking 1 and Pathfinder, at four sites on the martian surface. The results are remarkably consistent. At each of the locations, the same nine elements--silicon, iron, sulfur, magnesium, calcium, chlorine, sodium, potassium, and aluminum--constitute the bulk of the ingredients in the surface rocks. Chemical interactions with all of these elements can keep water from freezing at temperatures well below 0°C, the team reports tomorrow in Nature.

 火星水含有防凍劑的觀點(diǎn)來自一項(xiàng)對火星巖石和礦床的分析。來自美國國家航空航天管理局的一組科學(xué)家和兩個西班牙的研究機(jī)構(gòu)紛紛前來分析火星探測器所搜集的資料。這些探測器包括“勇氣號”和“機(jī)遇號”，以及更早的火星著陸裝置“海盜1號”和“探路者號”，它們從火星表面的四個地點(diǎn)搜集了資料。分析結(jié)果極為一致：在每個地點(diǎn)上，相同的9種元素——硅、鐵、硫、鎂、鈣、氯、納、鉀和鋁——構(gòu)成了表面巖石的大多數(shù)成分。研究人員在明天出版的《自然》雜志上報道說：跟所有這些元素之間所發(fā)生的化學(xué)作用，可以使水在大大低于0攝氏度的情況下而不至于凍結(jié)。

 Meanwhile, the team also ran climate models using martian temperature data. Those models show that the planet's atmosphere has always been too thin to support warmer-than-freezing temperatures. Yet satellite photos have shown ravines and features that look a lot like riverbeds and deltas on the martian surface, strongly suggesting that liquid water once flowed there. The only way to reconcile these two pieces of evidence, the team says, is to assume that water on Mars was very salty--as salty as that in the saltiest lakes on Earth--and thus would have resisted freezing. Eventually, as martian temperatures plunged to present-day levels, the water did freeze. In the planet's thin air, it then evaporated, leaving behind the telltale mineral deposits discovered by the four probes.

 同時，研究小組還利用火星的氣溫數(shù)據(jù)進(jìn)行了氣候模擬。模擬結(jié)果顯示，火星的大氣一直以來都很稀薄，無法說明擁有高于冰點(diǎn)的溫度。然而，衛(wèi)星圖像顯示出火星表面擁有溝壑以及看起來非常類似于河床和三角洲的地貌，有力地說明了液態(tài)水一度流經(jīng)那里。研究小組稱，把兩條證據(jù)協(xié)調(diào)起來的唯一辦法就是：假設(shè)火星當(dāng)時的水含鹽量特別高，相當(dāng)于地球上最咸的咸水湖的含鹽量，這樣就有可能抗拒凍結(jié)。最后，隨著火星溫度下降到目前的水平，火星水終于凍結(jié)了。當(dāng)時，在擁有稀薄空氣的地方，水則蒸發(fā)掉，留下可以作為證據(jù)的礦床，被四個火星探測器所發(fā)現(xiàn)。

 The paper's analysis is "consistent with the mineral-rich view we're obtaining from the rovers and the orbiters," says planetary scientist James Bell of Cornell University, a member of the Mars rover scientific team. "It's very likely that salty solutions played a role in shaping the martian landscape," agrees planetary scientist Itay Halevy of Harvard University, though he notes there might be other explanations for the mineral deposits.

 “該論文中的分析跟我們通過著陸探測器和軌道探測器所觀察到的結(jié)果一致：火星表面富含礦物，”火星探測器科研小組成員之一、康奈爾大學(xué)行星科學(xué)家詹姆斯·貝爾說?！昂芸赡茺}溶液在塑造火星地形方面起到了一定的作用，”哈佛大學(xué)行星科學(xué)家伊泰·阿萊維對分析結(jié)果表示同意，盡管他指出對于礦床可能還會有其他的解釋。