A vast ocean once covered a third of the surface of Mars, scientists revealed recently. Far from being a dusty red desert, our neighbouring planet was once wet and rainy-raising the prospect that it was home to extra-terrestrial life.
科學家最近披露，一個龐大的海洋曾覆蓋火星1/3地表，顯示這個鄰近地球的行星，絕非一個塵土飛揚的紅色沙漠，那裡反而一度多雨潮濕，更提高火星上有外星生命的可能性。
The researchers used a geographic information system, or GIS, to map the Martian terrain and conclude the ocean likely would have covered about 36 percent of the planet during the Noachian era around 3.5 billion years ago and contained 124 million cubic kilometers of water. The amount of water in the ancient ocean would have formed the equivalent of an 1,800-foot, or 550-meter deep layer of water spread out over the entire planet.
研究人員利用地理資訊系統，簡稱GIS，繪製火星地形圖，並得到結論：35億年前諾亞紀時期的海洋，很可能覆蓋約36%的火星地表，海洋中有1.24億立方公里的水。火星古老海洋中的水量，形成了相當於1800英尺或550公尺深的水層，散布在整個星球上。
The Martian sea-which has not been named- contained around a tenth of all the water found in Earth's oceans. Mars is slightly more than half the size of Earth. Long lived oceans may have teemed with microbes at a time when the life is thought to have also been starting on Earth.
火星的海洋迄未命名，其海水含量約為地球所有海洋的1/10左右。火星面積略大於地球的一半。年代久遠的海洋可能富含微生物，咸認當時也是地球上開始出現生物的時候。
Dr Brian Hynek, who took part in the study published in the June 13 journal Nature Geoscience, said Mars probably once had a water cycle like the Earth's-with rain falling into rivers and oceans, evaporating into the atmosphere and forming clouds. Using detailed maps of Maps created by orbiting NASA and European Space Agency spacecraft, the researchers looked at the remains of 52 river deltas, each fed by numerous river valleys. More than half were at the same altitude and appeared to mark the boundaries of a massive ocean.
這項研究發表於6月13日的《自然地球科學期刊》，參與研究工作的海涅克博士說，火星上可能曾出現一個類似地球的水循環系統：雨水落入河流和海洋中，蒸發到空氣中，再形成雲。利用在美國太空總署和歐洲太空總署軌道運行的太空船繪圖系統所繪製的詳細地圖，研究人員可以看見52個河川三角洲的遺址，每個三角洲匯聚無數河谷。其中半數以上高度相同，似乎標誌著一個巨大海洋的邊界。
The discovery is based on a detailed study of the dried-up river deltas and thousands of river valleys that scatter the Martian surface. Scientists from the University of Colorado at Boulder are unsure why the water vanished, but many suspect traces of the ocean remain in ice buried deep beneath the surface.
這項發現是根據詳細研究散布火星地表乾涸的河川三角洲和數以千計的河谷所得。但來自美國博爾德科羅拉多大學的科學家並不確定，為什麼後來海水消失了，但不少人懷疑，海洋的痕跡仍留在火星地表深處的冰層中。
Co-author Dr Gaetano Di Achille said: “On Earth, deltas and lakes are excellent collectors and preservers of signs of past life. If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past.” The idea of a large ancient ocean on Mars has been debated for two decades. However, the new study provides compelling evidence that the sea existed - and raises tantalizing questions about the planet's history. “One of the main questions we would like to answer is where all of the water on Mars went,” said Dr Di Achille.
研究共同作者狄艾奇里博士說：「在地球上，三角洲和湖泊是收藏和保存過去生命跡象最好的媒介。如果火星上曾出現生命，三角洲可能是解開火星過去生物之謎的關鍵。」這個火星上有大型古老海洋的想法已經持續爭論了20年。但這項新研究提供了令人信服的證據顯示，火星上的確存在著海洋，並提出有關火星歷史的誘人問題。「我們要回答的一個主要問題是：火星上的水到底到哪兒去了？」狄艾奇里博士說。
A second study also detected around 40,000 river valleys-four times more than have previously been spotted. The valleys were the source of sediment that was carried downstream and dumped into the deltas. Dr Hynek said:“The abundance of these river valleys required a significant amount of precipitation.” In addition, the large, ancient lakes upslope from the ancient Mars ocean likely formed inside impact craters and would have been filled by the transport of groundwater between the lakes and the ancient sea, according to the researchers. Twenty-nine of the 52 deltas were connected either to the ancient Mars ocean or to the groundwater table of the ocean and to several large, adjacent lakes. Future Mars missions-including NASA's Mars Atmosphere and Volatile Evolution project, due to blast off in 2013, should shed light in the mystery.
第2項研究也發現大約4萬個河谷，比過去發現的多4倍以上，河谷源自被沖刷到下游並傾倒到三角洲的沉積物。海涅克博士說：「這麼多河谷需要大量的降雨量。」此外，研究人員指出，在火星遠古時期海洋上游的古老大湖泊，可能在火星衝擊坑內部成形，並靠湖泊和古老海洋間地下水的流動填滿海水。52個三角洲中有29個不是和遠古時期的火星海洋銜接，就是和海洋地下水位及附近幾個大型湖泊相通。未來的火星任務，包括美國太空總署的火星大氣揮發演變計畫，預定2013年升空，應有助於進一步揭開神祕面紗。
Meanwhile, participants of a simulated Mars expedition “took off” for a 520-day “space trip”. Six people are sealed in the Mars-500 module, which will simulate all aspects of a journey to the Red Planet, with a 250-day trip onward, 30-day stay on “Mars surface” and a 240-day return flight. During nearly two years of isolation, the crew will experience many of the conditions likely to be encountered by astronauts on a real space flight, except for radiation and weightlessness.
此外，參加一項長達520天的「太空之旅」模擬火星探險計畫已經「起飛」。志願參加的6個人將密封在火星500太空艙中，模擬前往火星之旅的所有層面，去程有250天，再停留在「火星地表」30天，回程則有240天。經過近兩年的隔離，機組人員將經歷許多太空人在真正火星之旅中可能遭遇的種種情況，除了輻射和失重之外。
Three of the six crew members will leave the “spacecraft” and “walk” on Mars. Each of the crew members will receive about US$100,000 for participating in the mission. The crew will communicate with Earth via e-mails with a 40-minute delay. The “spacecraft” is equipped with a laboratory, living area, warehouse and mini-garden. The mission involved three Russians, a Frenchman, a Chinese, and an Italian. Chinese space trainer Wang Yue has been chosen as one of the volunteers for the Mars-500 test project. The Mars-500 test is being conducted by the Russian Federal Space Administration, Russian Academy and European Space Bureau. It is aimed at getting experience for a trip to Mars and to study the astronauts' psychology and physical state and work capabilities.
6名機組員中有3人將離開「太空艙」並在火星上「漫步」。參與這項任務的每名組員將獲得約10萬美元酬勞，他們並將透過電子郵件和地球通信，但會慢個40分鐘左右。「太空艙」裡有個實驗室、1個生活區、1個倉庫和小型花園。參與這項任務的包括3名俄羅斯人，法國人、中國人和義大利人各1名，中國太空教練王躍也被選中志願參加火星500計畫。火星500是由俄羅斯聯邦太空總署、俄羅斯科學院及歐洲太空局共同主辦，其目的是獲取火星之旅的經驗，並研究太空人的身心狀態和工作能力。
Hand out picture released on June 13, 2010 by the University of Colorado shows an illustration of what Mars might have looked like some 3.5 billion years ago when an ocean likely covered one-third of the planet's surface.
這張美國科羅拉多大學今年6月13日發布的照片顯示，約35億年前火星可能的形貌，當時海洋可能覆蓋火星1/3的地表。（法新社）