Using a radar instrument on an orbiting spacecraft, scientists have spotted what they said on July 25 appears to be a sizable salt-laden lake under ice on the southern polar plain of Mars, a body of water they called a possible habitat for microbial life. The reservoir they detected — roughly 20km in diameter, shaped like a rounded triangle and located about 1.5km beneath the ice surface — represents the first stable body of liquid water ever found on Mars.
Whether anywhere other than Earth has harbored life is one of the supreme questions in science, and the new findings offer tantalizing evidence, though no proof. Water is considered a fundamental ingredient for life. The researchers said it could take years to verify whether something is actually living in this body of water that resembles a subglacial lake on Earth, perhaps with a future mission drilling through the ice to sample the water below.
“This is the place on Mars where you have something that most resembles a habitat, a place where life could subsist,” said planetary scientist Roberto Orosei of Istituto Nazionale di Astrofisica in Italy, who led the research published in the journal Science. “This kind of environment is not exactly your ideal vacation, or a place where fish would swim,” Orosei added. “But there are terrestrial organisms that can survive and thrive, in fact, in similar environments. There are microorganisms on Earth that are capable of surviving even in ice.”
Photo: AFP
照片:法新社
The detection was made using data collected between May 2012 and December 2015 by an instrument aboard the European Space Agency’s Mars Express spacecraft that transmits radar pulses, which penetrate the Martian surface and ice caps. “This took us long years of data analysis and struggles to find a good method to be sure that what we were observing was unambiguously liquid water,” said study co-author Enrico Flamini, chief scientist at the Italian Space Agency during the research. The location’s radar profile resembled that of subglacial lakes found beneath Earth’s Antarctic and Greenland ice sheets.
Mars long ago was warmer and wetter, possessing significant bodies of water, as evidenced by dry lake beds and river valleys on its surface. There had been some signs of liquid water currently on Mars, including disputed evidence of water activity on Martian slopes, but not stable bodies of water. Orosei said the water in the Martian lake was below the normal freezing point but remained liquid thanks in large part to high levels of salts. Orosei estimated the water temperature at somewhere between minus 10°C and minus 70°C.
It remains to be seen if more subsurface reservoirs of water will be found or whether the newly discovered one is some sort of quirk, Orosei said. If others are detected and a network of subglacial lakes exists like on Earth, he said, that could indicate liquid water has persisted for millions of years or even dating back to 3 to 0.5 billion years ago when Mars was a more hospitable planet.
The question would be, Orosei added, whether any life forms that could have evolved long ago on Mars have found a way to survive until now. “Nobody dares to propose that there could be any more complex life form,” Orosei said.
(Reuters)
科學家在七月二十五日表示,藉助於一艘繞軌道運行太空船上的雷達儀器,他們在火星的南極平原冰層底下,探測到一片充滿鹽分的大型湖泊,這塊水體被認為是微生物生命可能的棲息地。這個偵測到的天然水庫直徑約二十公里,呈圓弧狀三角形,位於冰層表面下一點五公里處,是火星上第一次發現的穩定液態水體。
地球以外是否還有任何地方存有生命,這是科學界的終極問題之一,而這項發現儘管並非決定性物證,卻仍然提供吊人胃口的線索。水被視為生命的基本要素。研究人員表示,可能需要花上數年的時間,才能證實是否真有某種東西生存在這塊像地球冰下湖的水體中,或許未來的任務之一就是鑽透冰層,對底下的水進行抽樣檢測。
這篇發表於期刊《科學》的研究,其主持人羅貝托‧歐洛賽伊是義大利國家天文物理研究所的行星科學家,他表示:「這是火星上所找到最像棲息地的一個地方,生命或許能夠在此延續。」歐洛賽伊補充說:「像這樣的環境不太會是你的理想度假地點,或是會有魚類游來游去的地方。」他指出:「事實上,仍然有地球上的有機體可以在類似的環境中存活並繁衍。地球上甚至也有微生物能在冰裡存活。」
這項發現是借助於歐洲太空總署的「火星快車號」太空船上一台儀器在二○一二年五月到二○一五年十二月之間蒐集到的數據。這台儀器發送出雷達的脈衝波,能穿透火星表面與冰冠層。這份研究的共同作者恩利可‧法拉米尼是義大利太空總署的主任科學家,他在研究過程中表示:「我們耗費多年時間分析數據,努力找出一個正確的方法,以確認觀測的對象是毫無疑問的液態水。」這個地點的雷達數據與地球上南極洲與格陵蘭冰原底下發現的冰下湖非常相似。
很久以前,火星比現在溫暖且潮濕,表面乾涸的湖床與河谷也證明以前有相當大量的水體存在。也曾有跡象顯示目前火星上有液態水,包括受爭議的火星山坡水活動證據,但都不是穩定的水體。歐洛賽伊指出,火星湖裡的水溫度低於正常的冰點,但仍維持液態的一大部分原因可歸因於大量鹽分。他也估計湖水溫度約在攝氏零下十度到零下七十度之間。
歐洛賽伊表示,未來是否還會發現更多火星表面下的天然水庫,或是這個新發現其實是某種特殊情況,這都還需要繼續觀察。他指出,如果偵測到其他水體,並發現像地球上有一個冰下湖網絡存在,那可能暗示液態水已經持續存在了數百萬年,甚至能追溯到三十億至五億年前當火星是一個更適合居住的行星。
歐洛賽伊補充說,問題在於火星上是否有任何形式的生命,在很久以前就已開始演化,並找到方式存活至今。他表示:「沒有人敢說火星上會不會還有其他更複雜的生命形式。」
(台北時報章厚明譯)
Rice is an essential ingredient in Taiwanese cuisine. Many foods are made of rice, adding more variety to our cooking, such as rice cake, or “gui.” Wagui is made by steaming rice flour batter in a bowl. The term “gui” refers to a type of food made from rice, while “wa” refers to a bowl. The pronunciation of “gui” in Taiwanese Hokkien is similar to the word for “nobility” in Chinese, so it is common for people to prepare various types of gui, including wagui, as offerings to the gods or ancestors,. 米是台灣重要的主食,用米製成的食品十分多元,豐富我們的飲食,如米做成的「粿」。粿的意思是米做成的糕點,碗粿是將在來米漿倒入碗中蒸熟,因而得名。粿因為音同「貴」,因此碗粿等粿食常用作供品祭拜神明和祖先。 nobility (n.) 高貴,高尚;貴族 offering (n.) 供品 While Taiwan may not be
It’s no secret that Japanese people have a deep affection for noodles. Like in the rest of East Asia, noodles are an important staple food, second only to rice. Japanese people have enjoyed noodles for over 1,000 years. The first noodles came from China and were introduced around 800 CE. As time passed, noodles in Japan not only became widespread but also developed some unique Japanese characteristics. The three most popular types of noodles in Japan are ramen, soba, and udon. Ramen, typically made from wheat flour, is usually thin and firm. The dough is kneaded and left to
On Tuesday last week, the flame for this summer’s Paris Olympics was lit at the birthplace of the ancient Olympic Games in southern Greece in a meticulously choreographed ceremony. It will then be carried through Greece for more than 5,000km before being handed over to French organizers at the Athens venue used for the first modern Olympics in 1896. The pageantry at Olympia has been an essential part of every Olympics for nearly 90 years since the Games in Berlin. It’s meant to provide an ineluctable link between the modern event and the ancient Greek original on which it was initially modelled. Once
Drive-through (or drive-thru) restaurants provide people with the immense convenience of being able to purchase and pick up meals without needing to leave their vehicles. These restaurants have been around for decades, and their success has spawned a number of equally handy services. The drive-through concept originated with the drive-in restaurant, the first of which was established in the US in 1921. Patrons would order and eat the food that was delivered to their cars by workers called “carhops.” Ten years later, a drive-through service was introduced, but it was not until 1947 that the first exclusively drive-through restaurant opened its